mirror of https://github.com/Qortal/Brooklyn
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
4670 lines
148 KiB
4670 lines
148 KiB
// SPDX-License-Identifier: GPL-2.0+ |
|
/* |
|
* Read-Copy Update mechanism for mutual exclusion (tree-based version) |
|
* |
|
* Copyright IBM Corporation, 2008 |
|
* |
|
* Authors: Dipankar Sarma <[email protected]> |
|
* Manfred Spraul <[email protected]> |
|
* Paul E. McKenney <[email protected]> |
|
* |
|
* Based on the original work by Paul McKenney <[email protected]> |
|
* and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. |
|
* |
|
* For detailed explanation of Read-Copy Update mechanism see - |
|
* Documentation/RCU |
|
*/ |
|
|
|
#define pr_fmt(fmt) "rcu: " fmt |
|
|
|
#include <linux/types.h> |
|
#include <linux/kernel.h> |
|
#include <linux/init.h> |
|
#include <linux/spinlock.h> |
|
#include <linux/smp.h> |
|
#include <linux/rcupdate_wait.h> |
|
#include <linux/interrupt.h> |
|
#include <linux/sched.h> |
|
#include <linux/sched/debug.h> |
|
#include <linux/nmi.h> |
|
#include <linux/atomic.h> |
|
#include <linux/bitops.h> |
|
#include <linux/export.h> |
|
#include <linux/completion.h> |
|
#include <linux/moduleparam.h> |
|
#include <linux/percpu.h> |
|
#include <linux/notifier.h> |
|
#include <linux/cpu.h> |
|
#include <linux/mutex.h> |
|
#include <linux/time.h> |
|
#include <linux/kernel_stat.h> |
|
#include <linux/wait.h> |
|
#include <linux/kthread.h> |
|
#include <uapi/linux/sched/types.h> |
|
#include <linux/prefetch.h> |
|
#include <linux/delay.h> |
|
#include <linux/random.h> |
|
#include <linux/trace_events.h> |
|
#include <linux/suspend.h> |
|
#include <linux/ftrace.h> |
|
#include <linux/tick.h> |
|
#include <linux/sysrq.h> |
|
#include <linux/kprobes.h> |
|
#include <linux/gfp.h> |
|
#include <linux/oom.h> |
|
#include <linux/smpboot.h> |
|
#include <linux/jiffies.h> |
|
#include <linux/slab.h> |
|
#include <linux/sched/isolation.h> |
|
#include <linux/sched/clock.h> |
|
#include <linux/vmalloc.h> |
|
#include <linux/mm.h> |
|
#include <linux/kasan.h> |
|
#include "../time/tick-internal.h" |
|
|
|
#include "tree.h" |
|
#include "rcu.h" |
|
|
|
#ifdef MODULE_PARAM_PREFIX |
|
#undef MODULE_PARAM_PREFIX |
|
#endif |
|
#define MODULE_PARAM_PREFIX "rcutree." |
|
|
|
/* Data structures. */ |
|
|
|
/* |
|
* Steal a bit from the bottom of ->dynticks for idle entry/exit |
|
* control. Initially this is for TLB flushing. |
|
*/ |
|
#define RCU_DYNTICK_CTRL_MASK 0x1 |
|
#define RCU_DYNTICK_CTRL_CTR (RCU_DYNTICK_CTRL_MASK + 1) |
|
|
|
static DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_data, rcu_data) = { |
|
.dynticks_nesting = 1, |
|
.dynticks_nmi_nesting = DYNTICK_IRQ_NONIDLE, |
|
.dynticks = ATOMIC_INIT(RCU_DYNTICK_CTRL_CTR), |
|
#ifdef CONFIG_RCU_NOCB_CPU |
|
.cblist.flags = SEGCBLIST_SOFTIRQ_ONLY, |
|
#endif |
|
}; |
|
static struct rcu_state rcu_state = { |
|
.level = { &rcu_state.node[0] }, |
|
.gp_state = RCU_GP_IDLE, |
|
.gp_seq = (0UL - 300UL) << RCU_SEQ_CTR_SHIFT, |
|
.barrier_mutex = __MUTEX_INITIALIZER(rcu_state.barrier_mutex), |
|
.name = RCU_NAME, |
|
.abbr = RCU_ABBR, |
|
.exp_mutex = __MUTEX_INITIALIZER(rcu_state.exp_mutex), |
|
.exp_wake_mutex = __MUTEX_INITIALIZER(rcu_state.exp_wake_mutex), |
|
.ofl_lock = __RAW_SPIN_LOCK_UNLOCKED(rcu_state.ofl_lock), |
|
}; |
|
|
|
/* Dump rcu_node combining tree at boot to verify correct setup. */ |
|
static bool dump_tree; |
|
module_param(dump_tree, bool, 0444); |
|
/* By default, use RCU_SOFTIRQ instead of rcuc kthreads. */ |
|
static bool use_softirq = !IS_ENABLED(CONFIG_PREEMPT_RT); |
|
#ifndef CONFIG_PREEMPT_RT |
|
module_param(use_softirq, bool, 0444); |
|
#endif |
|
/* Control rcu_node-tree auto-balancing at boot time. */ |
|
static bool rcu_fanout_exact; |
|
module_param(rcu_fanout_exact, bool, 0444); |
|
/* Increase (but not decrease) the RCU_FANOUT_LEAF at boot time. */ |
|
static int rcu_fanout_leaf = RCU_FANOUT_LEAF; |
|
module_param(rcu_fanout_leaf, int, 0444); |
|
int rcu_num_lvls __read_mostly = RCU_NUM_LVLS; |
|
/* Number of rcu_nodes at specified level. */ |
|
int num_rcu_lvl[] = NUM_RCU_LVL_INIT; |
|
int rcu_num_nodes __read_mostly = NUM_RCU_NODES; /* Total # rcu_nodes in use. */ |
|
|
|
/* |
|
* The rcu_scheduler_active variable is initialized to the value |
|
* RCU_SCHEDULER_INACTIVE and transitions RCU_SCHEDULER_INIT just before the |
|
* first task is spawned. So when this variable is RCU_SCHEDULER_INACTIVE, |
|
* RCU can assume that there is but one task, allowing RCU to (for example) |
|
* optimize synchronize_rcu() to a simple barrier(). When this variable |
|
* is RCU_SCHEDULER_INIT, RCU must actually do all the hard work required |
|
* to detect real grace periods. This variable is also used to suppress |
|
* boot-time false positives from lockdep-RCU error checking. Finally, it |
|
* transitions from RCU_SCHEDULER_INIT to RCU_SCHEDULER_RUNNING after RCU |
|
* is fully initialized, including all of its kthreads having been spawned. |
|
*/ |
|
int rcu_scheduler_active __read_mostly; |
|
EXPORT_SYMBOL_GPL(rcu_scheduler_active); |
|
|
|
/* |
|
* The rcu_scheduler_fully_active variable transitions from zero to one |
|
* during the early_initcall() processing, which is after the scheduler |
|
* is capable of creating new tasks. So RCU processing (for example, |
|
* creating tasks for RCU priority boosting) must be delayed until after |
|
* rcu_scheduler_fully_active transitions from zero to one. We also |
|
* currently delay invocation of any RCU callbacks until after this point. |
|
* |
|
* It might later prove better for people registering RCU callbacks during |
|
* early boot to take responsibility for these callbacks, but one step at |
|
* a time. |
|
*/ |
|
static int rcu_scheduler_fully_active __read_mostly; |
|
|
|
static void rcu_report_qs_rnp(unsigned long mask, struct rcu_node *rnp, |
|
unsigned long gps, unsigned long flags); |
|
static void rcu_init_new_rnp(struct rcu_node *rnp_leaf); |
|
static void rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf); |
|
static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu); |
|
static void invoke_rcu_core(void); |
|
static void rcu_report_exp_rdp(struct rcu_data *rdp); |
|
static void sync_sched_exp_online_cleanup(int cpu); |
|
static void check_cb_ovld_locked(struct rcu_data *rdp, struct rcu_node *rnp); |
|
|
|
/* rcuc/rcub kthread realtime priority */ |
|
static int kthread_prio = IS_ENABLED(CONFIG_RCU_BOOST) ? 1 : 0; |
|
module_param(kthread_prio, int, 0444); |
|
|
|
/* Delay in jiffies for grace-period initialization delays, debug only. */ |
|
|
|
static int gp_preinit_delay; |
|
module_param(gp_preinit_delay, int, 0444); |
|
static int gp_init_delay; |
|
module_param(gp_init_delay, int, 0444); |
|
static int gp_cleanup_delay; |
|
module_param(gp_cleanup_delay, int, 0444); |
|
|
|
// Add delay to rcu_read_unlock() for strict grace periods. |
|
static int rcu_unlock_delay; |
|
#ifdef CONFIG_RCU_STRICT_GRACE_PERIOD |
|
module_param(rcu_unlock_delay, int, 0444); |
|
#endif |
|
|
|
/* |
|
* This rcu parameter is runtime-read-only. It reflects |
|
* a minimum allowed number of objects which can be cached |
|
* per-CPU. Object size is equal to one page. This value |
|
* can be changed at boot time. |
|
*/ |
|
static int rcu_min_cached_objs = 5; |
|
module_param(rcu_min_cached_objs, int, 0444); |
|
|
|
/* Retrieve RCU kthreads priority for rcutorture */ |
|
int rcu_get_gp_kthreads_prio(void) |
|
{ |
|
return kthread_prio; |
|
} |
|
EXPORT_SYMBOL_GPL(rcu_get_gp_kthreads_prio); |
|
|
|
/* |
|
* Number of grace periods between delays, normalized by the duration of |
|
* the delay. The longer the delay, the more the grace periods between |
|
* each delay. The reason for this normalization is that it means that, |
|
* for non-zero delays, the overall slowdown of grace periods is constant |
|
* regardless of the duration of the delay. This arrangement balances |
|
* the need for long delays to increase some race probabilities with the |
|
* need for fast grace periods to increase other race probabilities. |
|
*/ |
|
#define PER_RCU_NODE_PERIOD 3 /* Number of grace periods between delays. */ |
|
|
|
/* |
|
* Compute the mask of online CPUs for the specified rcu_node structure. |
|
* This will not be stable unless the rcu_node structure's ->lock is |
|
* held, but the bit corresponding to the current CPU will be stable |
|
* in most contexts. |
|
*/ |
|
static unsigned long rcu_rnp_online_cpus(struct rcu_node *rnp) |
|
{ |
|
return READ_ONCE(rnp->qsmaskinitnext); |
|
} |
|
|
|
/* |
|
* Return true if an RCU grace period is in progress. The READ_ONCE()s |
|
* permit this function to be invoked without holding the root rcu_node |
|
* structure's ->lock, but of course results can be subject to change. |
|
*/ |
|
static int rcu_gp_in_progress(void) |
|
{ |
|
return rcu_seq_state(rcu_seq_current(&rcu_state.gp_seq)); |
|
} |
|
|
|
/* |
|
* Return the number of callbacks queued on the specified CPU. |
|
* Handles both the nocbs and normal cases. |
|
*/ |
|
static long rcu_get_n_cbs_cpu(int cpu) |
|
{ |
|
struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); |
|
|
|
if (rcu_segcblist_is_enabled(&rdp->cblist)) |
|
return rcu_segcblist_n_cbs(&rdp->cblist); |
|
return 0; |
|
} |
|
|
|
void rcu_softirq_qs(void) |
|
{ |
|
rcu_qs(); |
|
rcu_preempt_deferred_qs(current); |
|
} |
|
|
|
/* |
|
* Record entry into an extended quiescent state. This is only to be |
|
* called when not already in an extended quiescent state, that is, |
|
* RCU is watching prior to the call to this function and is no longer |
|
* watching upon return. |
|
*/ |
|
static noinstr void rcu_dynticks_eqs_enter(void) |
|
{ |
|
struct rcu_data *rdp = this_cpu_ptr(&rcu_data); |
|
int seq; |
|
|
|
/* |
|
* CPUs seeing atomic_add_return() must see prior RCU read-side |
|
* critical sections, and we also must force ordering with the |
|
* next idle sojourn. |
|
*/ |
|
rcu_dynticks_task_trace_enter(); // Before ->dynticks update! |
|
seq = arch_atomic_add_return(RCU_DYNTICK_CTRL_CTR, &rdp->dynticks); |
|
// RCU is no longer watching. Better be in extended quiescent state! |
|
WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && |
|
(seq & RCU_DYNTICK_CTRL_CTR)); |
|
/* Better not have special action (TLB flush) pending! */ |
|
WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && |
|
(seq & RCU_DYNTICK_CTRL_MASK)); |
|
} |
|
|
|
/* |
|
* Record exit from an extended quiescent state. This is only to be |
|
* called from an extended quiescent state, that is, RCU is not watching |
|
* prior to the call to this function and is watching upon return. |
|
*/ |
|
static noinstr void rcu_dynticks_eqs_exit(void) |
|
{ |
|
struct rcu_data *rdp = this_cpu_ptr(&rcu_data); |
|
int seq; |
|
|
|
/* |
|
* CPUs seeing atomic_add_return() must see prior idle sojourns, |
|
* and we also must force ordering with the next RCU read-side |
|
* critical section. |
|
*/ |
|
seq = arch_atomic_add_return(RCU_DYNTICK_CTRL_CTR, &rdp->dynticks); |
|
// RCU is now watching. Better not be in an extended quiescent state! |
|
rcu_dynticks_task_trace_exit(); // After ->dynticks update! |
|
WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && |
|
!(seq & RCU_DYNTICK_CTRL_CTR)); |
|
if (seq & RCU_DYNTICK_CTRL_MASK) { |
|
arch_atomic_andnot(RCU_DYNTICK_CTRL_MASK, &rdp->dynticks); |
|
smp_mb__after_atomic(); /* _exit after clearing mask. */ |
|
} |
|
} |
|
|
|
/* |
|
* Reset the current CPU's ->dynticks counter to indicate that the |
|
* newly onlined CPU is no longer in an extended quiescent state. |
|
* This will either leave the counter unchanged, or increment it |
|
* to the next non-quiescent value. |
|
* |
|
* The non-atomic test/increment sequence works because the upper bits |
|
* of the ->dynticks counter are manipulated only by the corresponding CPU, |
|
* or when the corresponding CPU is offline. |
|
*/ |
|
static void rcu_dynticks_eqs_online(void) |
|
{ |
|
struct rcu_data *rdp = this_cpu_ptr(&rcu_data); |
|
|
|
if (atomic_read(&rdp->dynticks) & RCU_DYNTICK_CTRL_CTR) |
|
return; |
|
atomic_add(RCU_DYNTICK_CTRL_CTR, &rdp->dynticks); |
|
} |
|
|
|
/* |
|
* Is the current CPU in an extended quiescent state? |
|
* |
|
* No ordering, as we are sampling CPU-local information. |
|
*/ |
|
static __always_inline bool rcu_dynticks_curr_cpu_in_eqs(void) |
|
{ |
|
struct rcu_data *rdp = this_cpu_ptr(&rcu_data); |
|
|
|
return !(arch_atomic_read(&rdp->dynticks) & RCU_DYNTICK_CTRL_CTR); |
|
} |
|
|
|
/* |
|
* Snapshot the ->dynticks counter with full ordering so as to allow |
|
* stable comparison of this counter with past and future snapshots. |
|
*/ |
|
static int rcu_dynticks_snap(struct rcu_data *rdp) |
|
{ |
|
int snap = atomic_add_return(0, &rdp->dynticks); |
|
|
|
return snap & ~RCU_DYNTICK_CTRL_MASK; |
|
} |
|
|
|
/* |
|
* Return true if the snapshot returned from rcu_dynticks_snap() |
|
* indicates that RCU is in an extended quiescent state. |
|
*/ |
|
static bool rcu_dynticks_in_eqs(int snap) |
|
{ |
|
return !(snap & RCU_DYNTICK_CTRL_CTR); |
|
} |
|
|
|
/* Return true if the specified CPU is currently idle from an RCU viewpoint. */ |
|
bool rcu_is_idle_cpu(int cpu) |
|
{ |
|
struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); |
|
|
|
return rcu_dynticks_in_eqs(rcu_dynticks_snap(rdp)); |
|
} |
|
|
|
/* |
|
* Return true if the CPU corresponding to the specified rcu_data |
|
* structure has spent some time in an extended quiescent state since |
|
* rcu_dynticks_snap() returned the specified snapshot. |
|
*/ |
|
static bool rcu_dynticks_in_eqs_since(struct rcu_data *rdp, int snap) |
|
{ |
|
return snap != rcu_dynticks_snap(rdp); |
|
} |
|
|
|
/* |
|
* Return true if the referenced integer is zero while the specified |
|
* CPU remains within a single extended quiescent state. |
|
*/ |
|
bool rcu_dynticks_zero_in_eqs(int cpu, int *vp) |
|
{ |
|
struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); |
|
int snap; |
|
|
|
// If not quiescent, force back to earlier extended quiescent state. |
|
snap = atomic_read(&rdp->dynticks) & ~(RCU_DYNTICK_CTRL_MASK | |
|
RCU_DYNTICK_CTRL_CTR); |
|
|
|
smp_rmb(); // Order ->dynticks and *vp reads. |
|
if (READ_ONCE(*vp)) |
|
return false; // Non-zero, so report failure; |
|
smp_rmb(); // Order *vp read and ->dynticks re-read. |
|
|
|
// If still in the same extended quiescent state, we are good! |
|
return snap == (atomic_read(&rdp->dynticks) & ~RCU_DYNTICK_CTRL_MASK); |
|
} |
|
|
|
/* |
|
* Set the special (bottom) bit of the specified CPU so that it |
|
* will take special action (such as flushing its TLB) on the |
|
* next exit from an extended quiescent state. Returns true if |
|
* the bit was successfully set, or false if the CPU was not in |
|
* an extended quiescent state. |
|
*/ |
|
bool rcu_eqs_special_set(int cpu) |
|
{ |
|
int old; |
|
int new; |
|
int new_old; |
|
struct rcu_data *rdp = &per_cpu(rcu_data, cpu); |
|
|
|
new_old = atomic_read(&rdp->dynticks); |
|
do { |
|
old = new_old; |
|
if (old & RCU_DYNTICK_CTRL_CTR) |
|
return false; |
|
new = old | RCU_DYNTICK_CTRL_MASK; |
|
new_old = atomic_cmpxchg(&rdp->dynticks, old, new); |
|
} while (new_old != old); |
|
return true; |
|
} |
|
|
|
/* |
|
* Let the RCU core know that this CPU has gone through the scheduler, |
|
* which is a quiescent state. This is called when the need for a |
|
* quiescent state is urgent, so we burn an atomic operation and full |
|
* memory barriers to let the RCU core know about it, regardless of what |
|
* this CPU might (or might not) do in the near future. |
|
* |
|
* We inform the RCU core by emulating a zero-duration dyntick-idle period. |
|
* |
|
* The caller must have disabled interrupts and must not be idle. |
|
*/ |
|
notrace void rcu_momentary_dyntick_idle(void) |
|
{ |
|
int special; |
|
|
|
raw_cpu_write(rcu_data.rcu_need_heavy_qs, false); |
|
special = atomic_add_return(2 * RCU_DYNTICK_CTRL_CTR, |
|
&this_cpu_ptr(&rcu_data)->dynticks); |
|
/* It is illegal to call this from idle state. */ |
|
WARN_ON_ONCE(!(special & RCU_DYNTICK_CTRL_CTR)); |
|
rcu_preempt_deferred_qs(current); |
|
} |
|
EXPORT_SYMBOL_GPL(rcu_momentary_dyntick_idle); |
|
|
|
/** |
|
* rcu_is_cpu_rrupt_from_idle - see if 'interrupted' from idle |
|
* |
|
* If the current CPU is idle and running at a first-level (not nested) |
|
* interrupt, or directly, from idle, return true. |
|
* |
|
* The caller must have at least disabled IRQs. |
|
*/ |
|
static int rcu_is_cpu_rrupt_from_idle(void) |
|
{ |
|
long nesting; |
|
|
|
/* |
|
* Usually called from the tick; but also used from smp_function_call() |
|
* for expedited grace periods. This latter can result in running from |
|
* the idle task, instead of an actual IPI. |
|
*/ |
|
lockdep_assert_irqs_disabled(); |
|
|
|
/* Check for counter underflows */ |
|
RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nesting) < 0, |
|
"RCU dynticks_nesting counter underflow!"); |
|
RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nmi_nesting) <= 0, |
|
"RCU dynticks_nmi_nesting counter underflow/zero!"); |
|
|
|
/* Are we at first interrupt nesting level? */ |
|
nesting = __this_cpu_read(rcu_data.dynticks_nmi_nesting); |
|
if (nesting > 1) |
|
return false; |
|
|
|
/* |
|
* If we're not in an interrupt, we must be in the idle task! |
|
*/ |
|
WARN_ON_ONCE(!nesting && !is_idle_task(current)); |
|
|
|
/* Does CPU appear to be idle from an RCU standpoint? */ |
|
return __this_cpu_read(rcu_data.dynticks_nesting) == 0; |
|
} |
|
|
|
#define DEFAULT_RCU_BLIMIT (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD) ? 1000 : 10) |
|
// Maximum callbacks per rcu_do_batch ... |
|
#define DEFAULT_MAX_RCU_BLIMIT 10000 // ... even during callback flood. |
|
static long blimit = DEFAULT_RCU_BLIMIT; |
|
#define DEFAULT_RCU_QHIMARK 10000 // If this many pending, ignore blimit. |
|
static long qhimark = DEFAULT_RCU_QHIMARK; |
|
#define DEFAULT_RCU_QLOMARK 100 // Once only this many pending, use blimit. |
|
static long qlowmark = DEFAULT_RCU_QLOMARK; |
|
#define DEFAULT_RCU_QOVLD_MULT 2 |
|
#define DEFAULT_RCU_QOVLD (DEFAULT_RCU_QOVLD_MULT * DEFAULT_RCU_QHIMARK) |
|
static long qovld = DEFAULT_RCU_QOVLD; // If this many pending, hammer QS. |
|
static long qovld_calc = -1; // No pre-initialization lock acquisitions! |
|
|
|
module_param(blimit, long, 0444); |
|
module_param(qhimark, long, 0444); |
|
module_param(qlowmark, long, 0444); |
|
module_param(qovld, long, 0444); |
|
|
|
static ulong jiffies_till_first_fqs = IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD) ? 0 : ULONG_MAX; |
|
static ulong jiffies_till_next_fqs = ULONG_MAX; |
|
static bool rcu_kick_kthreads; |
|
static int rcu_divisor = 7; |
|
module_param(rcu_divisor, int, 0644); |
|
|
|
/* Force an exit from rcu_do_batch() after 3 milliseconds. */ |
|
static long rcu_resched_ns = 3 * NSEC_PER_MSEC; |
|
module_param(rcu_resched_ns, long, 0644); |
|
|
|
/* |
|
* How long the grace period must be before we start recruiting |
|
* quiescent-state help from rcu_note_context_switch(). |
|
*/ |
|
static ulong jiffies_till_sched_qs = ULONG_MAX; |
|
module_param(jiffies_till_sched_qs, ulong, 0444); |
|
static ulong jiffies_to_sched_qs; /* See adjust_jiffies_till_sched_qs(). */ |
|
module_param(jiffies_to_sched_qs, ulong, 0444); /* Display only! */ |
|
|
|
/* |
|
* Make sure that we give the grace-period kthread time to detect any |
|
* idle CPUs before taking active measures to force quiescent states. |
|
* However, don't go below 100 milliseconds, adjusted upwards for really |
|
* large systems. |
|
*/ |
|
static void adjust_jiffies_till_sched_qs(void) |
|
{ |
|
unsigned long j; |
|
|
|
/* If jiffies_till_sched_qs was specified, respect the request. */ |
|
if (jiffies_till_sched_qs != ULONG_MAX) { |
|
WRITE_ONCE(jiffies_to_sched_qs, jiffies_till_sched_qs); |
|
return; |
|
} |
|
/* Otherwise, set to third fqs scan, but bound below on large system. */ |
|
j = READ_ONCE(jiffies_till_first_fqs) + |
|
2 * READ_ONCE(jiffies_till_next_fqs); |
|
if (j < HZ / 10 + nr_cpu_ids / RCU_JIFFIES_FQS_DIV) |
|
j = HZ / 10 + nr_cpu_ids / RCU_JIFFIES_FQS_DIV; |
|
pr_info("RCU calculated value of scheduler-enlistment delay is %ld jiffies.\n", j); |
|
WRITE_ONCE(jiffies_to_sched_qs, j); |
|
} |
|
|
|
static int param_set_first_fqs_jiffies(const char *val, const struct kernel_param *kp) |
|
{ |
|
ulong j; |
|
int ret = kstrtoul(val, 0, &j); |
|
|
|
if (!ret) { |
|
WRITE_ONCE(*(ulong *)kp->arg, (j > HZ) ? HZ : j); |
|
adjust_jiffies_till_sched_qs(); |
|
} |
|
return ret; |
|
} |
|
|
|
static int param_set_next_fqs_jiffies(const char *val, const struct kernel_param *kp) |
|
{ |
|
ulong j; |
|
int ret = kstrtoul(val, 0, &j); |
|
|
|
if (!ret) { |
|
WRITE_ONCE(*(ulong *)kp->arg, (j > HZ) ? HZ : (j ?: 1)); |
|
adjust_jiffies_till_sched_qs(); |
|
} |
|
return ret; |
|
} |
|
|
|
static const struct kernel_param_ops first_fqs_jiffies_ops = { |
|
.set = param_set_first_fqs_jiffies, |
|
.get = param_get_ulong, |
|
}; |
|
|
|
static const struct kernel_param_ops next_fqs_jiffies_ops = { |
|
.set = param_set_next_fqs_jiffies, |
|
.get = param_get_ulong, |
|
}; |
|
|
|
module_param_cb(jiffies_till_first_fqs, &first_fqs_jiffies_ops, &jiffies_till_first_fqs, 0644); |
|
module_param_cb(jiffies_till_next_fqs, &next_fqs_jiffies_ops, &jiffies_till_next_fqs, 0644); |
|
module_param(rcu_kick_kthreads, bool, 0644); |
|
|
|
static void force_qs_rnp(int (*f)(struct rcu_data *rdp)); |
|
static int rcu_pending(int user); |
|
|
|
/* |
|
* Return the number of RCU GPs completed thus far for debug & stats. |
|
*/ |
|
unsigned long rcu_get_gp_seq(void) |
|
{ |
|
return READ_ONCE(rcu_state.gp_seq); |
|
} |
|
EXPORT_SYMBOL_GPL(rcu_get_gp_seq); |
|
|
|
/* |
|
* Return the number of RCU expedited batches completed thus far for |
|
* debug & stats. Odd numbers mean that a batch is in progress, even |
|
* numbers mean idle. The value returned will thus be roughly double |
|
* the cumulative batches since boot. |
|
*/ |
|
unsigned long rcu_exp_batches_completed(void) |
|
{ |
|
return rcu_state.expedited_sequence; |
|
} |
|
EXPORT_SYMBOL_GPL(rcu_exp_batches_completed); |
|
|
|
/* |
|
* Return the root node of the rcu_state structure. |
|
*/ |
|
static struct rcu_node *rcu_get_root(void) |
|
{ |
|
return &rcu_state.node[0]; |
|
} |
|
|
|
/* |
|
* Send along grace-period-related data for rcutorture diagnostics. |
|
*/ |
|
void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags, |
|
unsigned long *gp_seq) |
|
{ |
|
switch (test_type) { |
|
case RCU_FLAVOR: |
|
*flags = READ_ONCE(rcu_state.gp_flags); |
|
*gp_seq = rcu_seq_current(&rcu_state.gp_seq); |
|
break; |
|
default: |
|
break; |
|
} |
|
} |
|
EXPORT_SYMBOL_GPL(rcutorture_get_gp_data); |
|
|
|
/* |
|
* Enter an RCU extended quiescent state, which can be either the |
|
* idle loop or adaptive-tickless usermode execution. |
|
* |
|
* We crowbar the ->dynticks_nmi_nesting field to zero to allow for |
|
* the possibility of usermode upcalls having messed up our count |
|
* of interrupt nesting level during the prior busy period. |
|
*/ |
|
static noinstr void rcu_eqs_enter(bool user) |
|
{ |
|
struct rcu_data *rdp = this_cpu_ptr(&rcu_data); |
|
|
|
WARN_ON_ONCE(rdp->dynticks_nmi_nesting != DYNTICK_IRQ_NONIDLE); |
|
WRITE_ONCE(rdp->dynticks_nmi_nesting, 0); |
|
WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && |
|
rdp->dynticks_nesting == 0); |
|
if (rdp->dynticks_nesting != 1) { |
|
// RCU will still be watching, so just do accounting and leave. |
|
rdp->dynticks_nesting--; |
|
return; |
|
} |
|
|
|
lockdep_assert_irqs_disabled(); |
|
instrumentation_begin(); |
|
trace_rcu_dyntick(TPS("Start"), rdp->dynticks_nesting, 0, atomic_read(&rdp->dynticks)); |
|
WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current)); |
|
rdp = this_cpu_ptr(&rcu_data); |
|
rcu_prepare_for_idle(); |
|
rcu_preempt_deferred_qs(current); |
|
|
|
// instrumentation for the noinstr rcu_dynticks_eqs_enter() |
|
instrument_atomic_write(&rdp->dynticks, sizeof(rdp->dynticks)); |
|
|
|
instrumentation_end(); |
|
WRITE_ONCE(rdp->dynticks_nesting, 0); /* Avoid irq-access tearing. */ |
|
// RCU is watching here ... |
|
rcu_dynticks_eqs_enter(); |
|
// ... but is no longer watching here. |
|
rcu_dynticks_task_enter(); |
|
} |
|
|
|
/** |
|
* rcu_idle_enter - inform RCU that current CPU is entering idle |
|
* |
|
* Enter idle mode, in other words, -leave- the mode in which RCU |
|
* read-side critical sections can occur. (Though RCU read-side |
|
* critical sections can occur in irq handlers in idle, a possibility |
|
* handled by irq_enter() and irq_exit().) |
|
* |
|
* If you add or remove a call to rcu_idle_enter(), be sure to test with |
|
* CONFIG_RCU_EQS_DEBUG=y. |
|
*/ |
|
void rcu_idle_enter(void) |
|
{ |
|
lockdep_assert_irqs_disabled(); |
|
rcu_eqs_enter(false); |
|
} |
|
EXPORT_SYMBOL_GPL(rcu_idle_enter); |
|
|
|
#ifdef CONFIG_NO_HZ_FULL |
|
|
|
#if !defined(CONFIG_GENERIC_ENTRY) || !defined(CONFIG_KVM_XFER_TO_GUEST_WORK) |
|
/* |
|
* An empty function that will trigger a reschedule on |
|
* IRQ tail once IRQs get re-enabled on userspace/guest resume. |
|
*/ |
|
static void late_wakeup_func(struct irq_work *work) |
|
{ |
|
} |
|
|
|
static DEFINE_PER_CPU(struct irq_work, late_wakeup_work) = |
|
IRQ_WORK_INIT(late_wakeup_func); |
|
|
|
/* |
|
* If either: |
|
* |
|
* 1) the task is about to enter in guest mode and $ARCH doesn't support KVM generic work |
|
* 2) the task is about to enter in user mode and $ARCH doesn't support generic entry. |
|
* |
|
* In these cases the late RCU wake ups aren't supported in the resched loops and our |
|
* last resort is to fire a local irq_work that will trigger a reschedule once IRQs |
|
* get re-enabled again. |
|
*/ |
|
noinstr static void rcu_irq_work_resched(void) |
|
{ |
|
struct rcu_data *rdp = this_cpu_ptr(&rcu_data); |
|
|
|
if (IS_ENABLED(CONFIG_GENERIC_ENTRY) && !(current->flags & PF_VCPU)) |
|
return; |
|
|
|
if (IS_ENABLED(CONFIG_KVM_XFER_TO_GUEST_WORK) && (current->flags & PF_VCPU)) |
|
return; |
|
|
|
instrumentation_begin(); |
|
if (do_nocb_deferred_wakeup(rdp) && need_resched()) { |
|
irq_work_queue(this_cpu_ptr(&late_wakeup_work)); |
|
} |
|
instrumentation_end(); |
|
} |
|
|
|
#else |
|
static inline void rcu_irq_work_resched(void) { } |
|
#endif |
|
|
|
/** |
|
* rcu_user_enter - inform RCU that we are resuming userspace. |
|
* |
|
* Enter RCU idle mode right before resuming userspace. No use of RCU |
|
* is permitted between this call and rcu_user_exit(). This way the |
|
* CPU doesn't need to maintain the tick for RCU maintenance purposes |
|
* when the CPU runs in userspace. |
|
* |
|
* If you add or remove a call to rcu_user_enter(), be sure to test with |
|
* CONFIG_RCU_EQS_DEBUG=y. |
|
*/ |
|
noinstr void rcu_user_enter(void) |
|
{ |
|
lockdep_assert_irqs_disabled(); |
|
|
|
/* |
|
* Other than generic entry implementation, we may be past the last |
|
* rescheduling opportunity in the entry code. Trigger a self IPI |
|
* that will fire and reschedule once we resume in user/guest mode. |
|
*/ |
|
rcu_irq_work_resched(); |
|
rcu_eqs_enter(true); |
|
} |
|
|
|
#endif /* CONFIG_NO_HZ_FULL */ |
|
|
|
/** |
|
* rcu_nmi_exit - inform RCU of exit from NMI context |
|
* |
|
* If we are returning from the outermost NMI handler that interrupted an |
|
* RCU-idle period, update rdp->dynticks and rdp->dynticks_nmi_nesting |
|
* to let the RCU grace-period handling know that the CPU is back to |
|
* being RCU-idle. |
|
* |
|
* If you add or remove a call to rcu_nmi_exit(), be sure to test |
|
* with CONFIG_RCU_EQS_DEBUG=y. |
|
*/ |
|
noinstr void rcu_nmi_exit(void) |
|
{ |
|
struct rcu_data *rdp = this_cpu_ptr(&rcu_data); |
|
|
|
instrumentation_begin(); |
|
/* |
|
* Check for ->dynticks_nmi_nesting underflow and bad ->dynticks. |
|
* (We are exiting an NMI handler, so RCU better be paying attention |
|
* to us!) |
|
*/ |
|
WARN_ON_ONCE(rdp->dynticks_nmi_nesting <= 0); |
|
WARN_ON_ONCE(rcu_dynticks_curr_cpu_in_eqs()); |
|
|
|
/* |
|
* If the nesting level is not 1, the CPU wasn't RCU-idle, so |
|
* leave it in non-RCU-idle state. |
|
*/ |
|
if (rdp->dynticks_nmi_nesting != 1) { |
|
trace_rcu_dyntick(TPS("--="), rdp->dynticks_nmi_nesting, rdp->dynticks_nmi_nesting - 2, |
|
atomic_read(&rdp->dynticks)); |
|
WRITE_ONCE(rdp->dynticks_nmi_nesting, /* No store tearing. */ |
|
rdp->dynticks_nmi_nesting - 2); |
|
instrumentation_end(); |
|
return; |
|
} |
|
|
|
/* This NMI interrupted an RCU-idle CPU, restore RCU-idleness. */ |
|
trace_rcu_dyntick(TPS("Startirq"), rdp->dynticks_nmi_nesting, 0, atomic_read(&rdp->dynticks)); |
|
WRITE_ONCE(rdp->dynticks_nmi_nesting, 0); /* Avoid store tearing. */ |
|
|
|
if (!in_nmi()) |
|
rcu_prepare_for_idle(); |
|
|
|
// instrumentation for the noinstr rcu_dynticks_eqs_enter() |
|
instrument_atomic_write(&rdp->dynticks, sizeof(rdp->dynticks)); |
|
instrumentation_end(); |
|
|
|
// RCU is watching here ... |
|
rcu_dynticks_eqs_enter(); |
|
// ... but is no longer watching here. |
|
|
|
if (!in_nmi()) |
|
rcu_dynticks_task_enter(); |
|
} |
|
|
|
/** |
|
* rcu_irq_exit - inform RCU that current CPU is exiting irq towards idle |
|
* |
|
* Exit from an interrupt handler, which might possibly result in entering |
|
* idle mode, in other words, leaving the mode in which read-side critical |
|
* sections can occur. The caller must have disabled interrupts. |
|
* |
|
* This code assumes that the idle loop never does anything that might |
|
* result in unbalanced calls to irq_enter() and irq_exit(). If your |
|
* architecture's idle loop violates this assumption, RCU will give you what |
|
* you deserve, good and hard. But very infrequently and irreproducibly. |
|
* |
|
* Use things like work queues to work around this limitation. |
|
* |
|
* You have been warned. |
|
* |
|
* If you add or remove a call to rcu_irq_exit(), be sure to test with |
|
* CONFIG_RCU_EQS_DEBUG=y. |
|
*/ |
|
void noinstr rcu_irq_exit(void) |
|
{ |
|
lockdep_assert_irqs_disabled(); |
|
rcu_nmi_exit(); |
|
} |
|
|
|
/** |
|
* rcu_irq_exit_preempt - Inform RCU that current CPU is exiting irq |
|
* towards in kernel preemption |
|
* |
|
* Same as rcu_irq_exit() but has a sanity check that scheduling is safe |
|
* from RCU point of view. Invoked from return from interrupt before kernel |
|
* preemption. |
|
*/ |
|
void rcu_irq_exit_preempt(void) |
|
{ |
|
lockdep_assert_irqs_disabled(); |
|
rcu_nmi_exit(); |
|
|
|
RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nesting) <= 0, |
|
"RCU dynticks_nesting counter underflow/zero!"); |
|
RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nmi_nesting) != |
|
DYNTICK_IRQ_NONIDLE, |
|
"Bad RCU dynticks_nmi_nesting counter\n"); |
|
RCU_LOCKDEP_WARN(rcu_dynticks_curr_cpu_in_eqs(), |
|
"RCU in extended quiescent state!"); |
|
} |
|
|
|
#ifdef CONFIG_PROVE_RCU |
|
/** |
|
* rcu_irq_exit_check_preempt - Validate that scheduling is possible |
|
*/ |
|
void rcu_irq_exit_check_preempt(void) |
|
{ |
|
lockdep_assert_irqs_disabled(); |
|
|
|
RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nesting) <= 0, |
|
"RCU dynticks_nesting counter underflow/zero!"); |
|
RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nmi_nesting) != |
|
DYNTICK_IRQ_NONIDLE, |
|
"Bad RCU dynticks_nmi_nesting counter\n"); |
|
RCU_LOCKDEP_WARN(rcu_dynticks_curr_cpu_in_eqs(), |
|
"RCU in extended quiescent state!"); |
|
} |
|
#endif /* #ifdef CONFIG_PROVE_RCU */ |
|
|
|
/* |
|
* Wrapper for rcu_irq_exit() where interrupts are enabled. |
|
* |
|
* If you add or remove a call to rcu_irq_exit_irqson(), be sure to test |
|
* with CONFIG_RCU_EQS_DEBUG=y. |
|
*/ |
|
void rcu_irq_exit_irqson(void) |
|
{ |
|
unsigned long flags; |
|
|
|
local_irq_save(flags); |
|
rcu_irq_exit(); |
|
local_irq_restore(flags); |
|
} |
|
|
|
/* |
|
* Exit an RCU extended quiescent state, which can be either the |
|
* idle loop or adaptive-tickless usermode execution. |
|
* |
|
* We crowbar the ->dynticks_nmi_nesting field to DYNTICK_IRQ_NONIDLE to |
|
* allow for the possibility of usermode upcalls messing up our count of |
|
* interrupt nesting level during the busy period that is just now starting. |
|
*/ |
|
static void noinstr rcu_eqs_exit(bool user) |
|
{ |
|
struct rcu_data *rdp; |
|
long oldval; |
|
|
|
lockdep_assert_irqs_disabled(); |
|
rdp = this_cpu_ptr(&rcu_data); |
|
oldval = rdp->dynticks_nesting; |
|
WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && oldval < 0); |
|
if (oldval) { |
|
// RCU was already watching, so just do accounting and leave. |
|
rdp->dynticks_nesting++; |
|
return; |
|
} |
|
rcu_dynticks_task_exit(); |
|
// RCU is not watching here ... |
|
rcu_dynticks_eqs_exit(); |
|
// ... but is watching here. |
|
instrumentation_begin(); |
|
|
|
// instrumentation for the noinstr rcu_dynticks_eqs_exit() |
|
instrument_atomic_write(&rdp->dynticks, sizeof(rdp->dynticks)); |
|
|
|
rcu_cleanup_after_idle(); |
|
trace_rcu_dyntick(TPS("End"), rdp->dynticks_nesting, 1, atomic_read(&rdp->dynticks)); |
|
WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current)); |
|
WRITE_ONCE(rdp->dynticks_nesting, 1); |
|
WARN_ON_ONCE(rdp->dynticks_nmi_nesting); |
|
WRITE_ONCE(rdp->dynticks_nmi_nesting, DYNTICK_IRQ_NONIDLE); |
|
instrumentation_end(); |
|
} |
|
|
|
/** |
|
* rcu_idle_exit - inform RCU that current CPU is leaving idle |
|
* |
|
* Exit idle mode, in other words, -enter- the mode in which RCU |
|
* read-side critical sections can occur. |
|
* |
|
* If you add or remove a call to rcu_idle_exit(), be sure to test with |
|
* CONFIG_RCU_EQS_DEBUG=y. |
|
*/ |
|
void rcu_idle_exit(void) |
|
{ |
|
unsigned long flags; |
|
|
|
local_irq_save(flags); |
|
rcu_eqs_exit(false); |
|
local_irq_restore(flags); |
|
} |
|
EXPORT_SYMBOL_GPL(rcu_idle_exit); |
|
|
|
#ifdef CONFIG_NO_HZ_FULL |
|
/** |
|
* rcu_user_exit - inform RCU that we are exiting userspace. |
|
* |
|
* Exit RCU idle mode while entering the kernel because it can |
|
* run a RCU read side critical section anytime. |
|
* |
|
* If you add or remove a call to rcu_user_exit(), be sure to test with |
|
* CONFIG_RCU_EQS_DEBUG=y. |
|
*/ |
|
void noinstr rcu_user_exit(void) |
|
{ |
|
rcu_eqs_exit(1); |
|
} |
|
|
|
/** |
|
* __rcu_irq_enter_check_tick - Enable scheduler tick on CPU if RCU needs it. |
|
* |
|
* The scheduler tick is not normally enabled when CPUs enter the kernel |
|
* from nohz_full userspace execution. After all, nohz_full userspace |
|
* execution is an RCU quiescent state and the time executing in the kernel |
|
* is quite short. Except of course when it isn't. And it is not hard to |
|
* cause a large system to spend tens of seconds or even minutes looping |
|
* in the kernel, which can cause a number of problems, include RCU CPU |
|
* stall warnings. |
|
* |
|
* Therefore, if a nohz_full CPU fails to report a quiescent state |
|
* in a timely manner, the RCU grace-period kthread sets that CPU's |
|
* ->rcu_urgent_qs flag with the expectation that the next interrupt or |
|
* exception will invoke this function, which will turn on the scheduler |
|
* tick, which will enable RCU to detect that CPU's quiescent states, |
|
* for example, due to cond_resched() calls in CONFIG_PREEMPT=n kernels. |
|
* The tick will be disabled once a quiescent state is reported for |
|
* this CPU. |
|
* |
|
* Of course, in carefully tuned systems, there might never be an |
|
* interrupt or exception. In that case, the RCU grace-period kthread |
|
* will eventually cause one to happen. However, in less carefully |
|
* controlled environments, this function allows RCU to get what it |
|
* needs without creating otherwise useless interruptions. |
|
*/ |
|
void __rcu_irq_enter_check_tick(void) |
|
{ |
|
struct rcu_data *rdp = this_cpu_ptr(&rcu_data); |
|
|
|
// If we're here from NMI there's nothing to do. |
|
if (in_nmi()) |
|
return; |
|
|
|
RCU_LOCKDEP_WARN(rcu_dynticks_curr_cpu_in_eqs(), |
|
"Illegal rcu_irq_enter_check_tick() from extended quiescent state"); |
|
|
|
if (!tick_nohz_full_cpu(rdp->cpu) || |
|
!READ_ONCE(rdp->rcu_urgent_qs) || |
|
READ_ONCE(rdp->rcu_forced_tick)) { |
|
// RCU doesn't need nohz_full help from this CPU, or it is |
|
// already getting that help. |
|
return; |
|
} |
|
|
|
// We get here only when not in an extended quiescent state and |
|
// from interrupts (as opposed to NMIs). Therefore, (1) RCU is |
|
// already watching and (2) The fact that we are in an interrupt |
|
// handler and that the rcu_node lock is an irq-disabled lock |
|
// prevents self-deadlock. So we can safely recheck under the lock. |
|
// Note that the nohz_full state currently cannot change. |
|
raw_spin_lock_rcu_node(rdp->mynode); |
|
if (rdp->rcu_urgent_qs && !rdp->rcu_forced_tick) { |
|
// A nohz_full CPU is in the kernel and RCU needs a |
|
// quiescent state. Turn on the tick! |
|
WRITE_ONCE(rdp->rcu_forced_tick, true); |
|
tick_dep_set_cpu(rdp->cpu, TICK_DEP_BIT_RCU); |
|
} |
|
raw_spin_unlock_rcu_node(rdp->mynode); |
|
} |
|
#endif /* CONFIG_NO_HZ_FULL */ |
|
|
|
/** |
|
* rcu_nmi_enter - inform RCU of entry to NMI context |
|
* |
|
* If the CPU was idle from RCU's viewpoint, update rdp->dynticks and |
|
* rdp->dynticks_nmi_nesting to let the RCU grace-period handling know |
|
* that the CPU is active. This implementation permits nested NMIs, as |
|
* long as the nesting level does not overflow an int. (You will probably |
|
* run out of stack space first.) |
|
* |
|
* If you add or remove a call to rcu_nmi_enter(), be sure to test |
|
* with CONFIG_RCU_EQS_DEBUG=y. |
|
*/ |
|
noinstr void rcu_nmi_enter(void) |
|
{ |
|
long incby = 2; |
|
struct rcu_data *rdp = this_cpu_ptr(&rcu_data); |
|
|
|
/* Complain about underflow. */ |
|
WARN_ON_ONCE(rdp->dynticks_nmi_nesting < 0); |
|
|
|
/* |
|
* If idle from RCU viewpoint, atomically increment ->dynticks |
|
* to mark non-idle and increment ->dynticks_nmi_nesting by one. |
|
* Otherwise, increment ->dynticks_nmi_nesting by two. This means |
|
* if ->dynticks_nmi_nesting is equal to one, we are guaranteed |
|
* to be in the outermost NMI handler that interrupted an RCU-idle |
|
* period (observation due to Andy Lutomirski). |
|
*/ |
|
if (rcu_dynticks_curr_cpu_in_eqs()) { |
|
|
|
if (!in_nmi()) |
|
rcu_dynticks_task_exit(); |
|
|
|
// RCU is not watching here ... |
|
rcu_dynticks_eqs_exit(); |
|
// ... but is watching here. |
|
|
|
if (!in_nmi()) { |
|
instrumentation_begin(); |
|
rcu_cleanup_after_idle(); |
|
instrumentation_end(); |
|
} |
|
|
|
instrumentation_begin(); |
|
// instrumentation for the noinstr rcu_dynticks_curr_cpu_in_eqs() |
|
instrument_atomic_read(&rdp->dynticks, sizeof(rdp->dynticks)); |
|
// instrumentation for the noinstr rcu_dynticks_eqs_exit() |
|
instrument_atomic_write(&rdp->dynticks, sizeof(rdp->dynticks)); |
|
|
|
incby = 1; |
|
} else if (!in_nmi()) { |
|
instrumentation_begin(); |
|
rcu_irq_enter_check_tick(); |
|
} else { |
|
instrumentation_begin(); |
|
} |
|
|
|
trace_rcu_dyntick(incby == 1 ? TPS("Endirq") : TPS("++="), |
|
rdp->dynticks_nmi_nesting, |
|
rdp->dynticks_nmi_nesting + incby, atomic_read(&rdp->dynticks)); |
|
instrumentation_end(); |
|
WRITE_ONCE(rdp->dynticks_nmi_nesting, /* Prevent store tearing. */ |
|
rdp->dynticks_nmi_nesting + incby); |
|
barrier(); |
|
} |
|
|
|
/** |
|
* rcu_irq_enter - inform RCU that current CPU is entering irq away from idle |
|
* |
|
* Enter an interrupt handler, which might possibly result in exiting |
|
* idle mode, in other words, entering the mode in which read-side critical |
|
* sections can occur. The caller must have disabled interrupts. |
|
* |
|
* Note that the Linux kernel is fully capable of entering an interrupt |
|
* handler that it never exits, for example when doing upcalls to user mode! |
|
* This code assumes that the idle loop never does upcalls to user mode. |
|
* If your architecture's idle loop does do upcalls to user mode (or does |
|
* anything else that results in unbalanced calls to the irq_enter() and |
|
* irq_exit() functions), RCU will give you what you deserve, good and hard. |
|
* But very infrequently and irreproducibly. |
|
* |
|
* Use things like work queues to work around this limitation. |
|
* |
|
* You have been warned. |
|
* |
|
* If you add or remove a call to rcu_irq_enter(), be sure to test with |
|
* CONFIG_RCU_EQS_DEBUG=y. |
|
*/ |
|
noinstr void rcu_irq_enter(void) |
|
{ |
|
lockdep_assert_irqs_disabled(); |
|
rcu_nmi_enter(); |
|
} |
|
|
|
/* |
|
* Wrapper for rcu_irq_enter() where interrupts are enabled. |
|
* |
|
* If you add or remove a call to rcu_irq_enter_irqson(), be sure to test |
|
* with CONFIG_RCU_EQS_DEBUG=y. |
|
*/ |
|
void rcu_irq_enter_irqson(void) |
|
{ |
|
unsigned long flags; |
|
|
|
local_irq_save(flags); |
|
rcu_irq_enter(); |
|
local_irq_restore(flags); |
|
} |
|
|
|
/* |
|
* If any sort of urgency was applied to the current CPU (for example, |
|
* the scheduler-clock interrupt was enabled on a nohz_full CPU) in order |
|
* to get to a quiescent state, disable it. |
|
*/ |
|
static void rcu_disable_urgency_upon_qs(struct rcu_data *rdp) |
|
{ |
|
raw_lockdep_assert_held_rcu_node(rdp->mynode); |
|
WRITE_ONCE(rdp->rcu_urgent_qs, false); |
|
WRITE_ONCE(rdp->rcu_need_heavy_qs, false); |
|
if (tick_nohz_full_cpu(rdp->cpu) && rdp->rcu_forced_tick) { |
|
tick_dep_clear_cpu(rdp->cpu, TICK_DEP_BIT_RCU); |
|
WRITE_ONCE(rdp->rcu_forced_tick, false); |
|
} |
|
} |
|
|
|
/** |
|
* rcu_is_watching - see if RCU thinks that the current CPU is not idle |
|
* |
|
* Return true if RCU is watching the running CPU, which means that this |
|
* CPU can safely enter RCU read-side critical sections. In other words, |
|
* if the current CPU is not in its idle loop or is in an interrupt or |
|
* NMI handler, return true. |
|
* |
|
* Make notrace because it can be called by the internal functions of |
|
* ftrace, and making this notrace removes unnecessary recursion calls. |
|
*/ |
|
notrace bool rcu_is_watching(void) |
|
{ |
|
bool ret; |
|
|
|
preempt_disable_notrace(); |
|
ret = !rcu_dynticks_curr_cpu_in_eqs(); |
|
preempt_enable_notrace(); |
|
return ret; |
|
} |
|
EXPORT_SYMBOL_GPL(rcu_is_watching); |
|
|
|
/* |
|
* If a holdout task is actually running, request an urgent quiescent |
|
* state from its CPU. This is unsynchronized, so migrations can cause |
|
* the request to go to the wrong CPU. Which is OK, all that will happen |
|
* is that the CPU's next context switch will be a bit slower and next |
|
* time around this task will generate another request. |
|
*/ |
|
void rcu_request_urgent_qs_task(struct task_struct *t) |
|
{ |
|
int cpu; |
|
|
|
barrier(); |
|
cpu = task_cpu(t); |
|
if (!task_curr(t)) |
|
return; /* This task is not running on that CPU. */ |
|
smp_store_release(per_cpu_ptr(&rcu_data.rcu_urgent_qs, cpu), true); |
|
} |
|
|
|
#if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU) |
|
|
|
/* |
|
* Is the current CPU online as far as RCU is concerned? |
|
* |
|
* Disable preemption to avoid false positives that could otherwise |
|
* happen due to the current CPU number being sampled, this task being |
|
* preempted, its old CPU being taken offline, resuming on some other CPU, |
|
* then determining that its old CPU is now offline. |
|
* |
|
* Disable checking if in an NMI handler because we cannot safely |
|
* report errors from NMI handlers anyway. In addition, it is OK to use |
|
* RCU on an offline processor during initial boot, hence the check for |
|
* rcu_scheduler_fully_active. |
|
*/ |
|
bool rcu_lockdep_current_cpu_online(void) |
|
{ |
|
struct rcu_data *rdp; |
|
struct rcu_node *rnp; |
|
bool ret = false; |
|
|
|
if (in_nmi() || !rcu_scheduler_fully_active) |
|
return true; |
|
preempt_disable_notrace(); |
|
rdp = this_cpu_ptr(&rcu_data); |
|
rnp = rdp->mynode; |
|
if (rdp->grpmask & rcu_rnp_online_cpus(rnp) || READ_ONCE(rnp->ofl_seq) & 0x1) |
|
ret = true; |
|
preempt_enable_notrace(); |
|
return ret; |
|
} |
|
EXPORT_SYMBOL_GPL(rcu_lockdep_current_cpu_online); |
|
|
|
#endif /* #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU) */ |
|
|
|
/* |
|
* We are reporting a quiescent state on behalf of some other CPU, so |
|
* it is our responsibility to check for and handle potential overflow |
|
* of the rcu_node ->gp_seq counter with respect to the rcu_data counters. |
|
* After all, the CPU might be in deep idle state, and thus executing no |
|
* code whatsoever. |
|
*/ |
|
static void rcu_gpnum_ovf(struct rcu_node *rnp, struct rcu_data *rdp) |
|
{ |
|
raw_lockdep_assert_held_rcu_node(rnp); |
|
if (ULONG_CMP_LT(rcu_seq_current(&rdp->gp_seq) + ULONG_MAX / 4, |
|
rnp->gp_seq)) |
|
WRITE_ONCE(rdp->gpwrap, true); |
|
if (ULONG_CMP_LT(rdp->rcu_iw_gp_seq + ULONG_MAX / 4, rnp->gp_seq)) |
|
rdp->rcu_iw_gp_seq = rnp->gp_seq + ULONG_MAX / 4; |
|
} |
|
|
|
/* |
|
* Snapshot the specified CPU's dynticks counter so that we can later |
|
* credit them with an implicit quiescent state. Return 1 if this CPU |
|
* is in dynticks idle mode, which is an extended quiescent state. |
|
*/ |
|
static int dyntick_save_progress_counter(struct rcu_data *rdp) |
|
{ |
|
rdp->dynticks_snap = rcu_dynticks_snap(rdp); |
|
if (rcu_dynticks_in_eqs(rdp->dynticks_snap)) { |
|
trace_rcu_fqs(rcu_state.name, rdp->gp_seq, rdp->cpu, TPS("dti")); |
|
rcu_gpnum_ovf(rdp->mynode, rdp); |
|
return 1; |
|
} |
|
return 0; |
|
} |
|
|
|
/* |
|
* Return true if the specified CPU has passed through a quiescent |
|
* state by virtue of being in or having passed through an dynticks |
|
* idle state since the last call to dyntick_save_progress_counter() |
|
* for this same CPU, or by virtue of having been offline. |
|
*/ |
|
static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) |
|
{ |
|
unsigned long jtsq; |
|
bool *rnhqp; |
|
bool *ruqp; |
|
struct rcu_node *rnp = rdp->mynode; |
|
|
|
/* |
|
* If the CPU passed through or entered a dynticks idle phase with |
|
* no active irq/NMI handlers, then we can safely pretend that the CPU |
|
* already acknowledged the request to pass through a quiescent |
|
* state. Either way, that CPU cannot possibly be in an RCU |
|
* read-side critical section that started before the beginning |
|
* of the current RCU grace period. |
|
*/ |
|
if (rcu_dynticks_in_eqs_since(rdp, rdp->dynticks_snap)) { |
|
trace_rcu_fqs(rcu_state.name, rdp->gp_seq, rdp->cpu, TPS("dti")); |
|
rcu_gpnum_ovf(rnp, rdp); |
|
return 1; |
|
} |
|
|
|
/* |
|
* Complain if a CPU that is considered to be offline from RCU's |
|
* perspective has not yet reported a quiescent state. After all, |
|
* the offline CPU should have reported a quiescent state during |
|
* the CPU-offline process, or, failing that, by rcu_gp_init() |
|
* if it ran concurrently with either the CPU going offline or the |
|
* last task on a leaf rcu_node structure exiting its RCU read-side |
|
* critical section while all CPUs corresponding to that structure |
|
* are offline. This added warning detects bugs in any of these |
|
* code paths. |
|
* |
|
* The rcu_node structure's ->lock is held here, which excludes |
|
* the relevant portions the CPU-hotplug code, the grace-period |
|
* initialization code, and the rcu_read_unlock() code paths. |
|
* |
|
* For more detail, please refer to the "Hotplug CPU" section |
|
* of RCU's Requirements documentation. |
|
*/ |
|
if (WARN_ON_ONCE(!(rdp->grpmask & rcu_rnp_online_cpus(rnp)))) { |
|
bool onl; |
|
struct rcu_node *rnp1; |
|
|
|
pr_info("%s: grp: %d-%d level: %d ->gp_seq %ld ->completedqs %ld\n", |
|
__func__, rnp->grplo, rnp->grphi, rnp->level, |
|
(long)rnp->gp_seq, (long)rnp->completedqs); |
|
for (rnp1 = rnp; rnp1; rnp1 = rnp1->parent) |
|
pr_info("%s: %d:%d ->qsmask %#lx ->qsmaskinit %#lx ->qsmaskinitnext %#lx ->rcu_gp_init_mask %#lx\n", |
|
__func__, rnp1->grplo, rnp1->grphi, rnp1->qsmask, rnp1->qsmaskinit, rnp1->qsmaskinitnext, rnp1->rcu_gp_init_mask); |
|
onl = !!(rdp->grpmask & rcu_rnp_online_cpus(rnp)); |
|
pr_info("%s %d: %c online: %ld(%d) offline: %ld(%d)\n", |
|
__func__, rdp->cpu, ".o"[onl], |
|
(long)rdp->rcu_onl_gp_seq, rdp->rcu_onl_gp_flags, |
|
(long)rdp->rcu_ofl_gp_seq, rdp->rcu_ofl_gp_flags); |
|
return 1; /* Break things loose after complaining. */ |
|
} |
|
|
|
/* |
|
* A CPU running for an extended time within the kernel can |
|
* delay RCU grace periods: (1) At age jiffies_to_sched_qs, |
|
* set .rcu_urgent_qs, (2) At age 2*jiffies_to_sched_qs, set |
|
* both .rcu_need_heavy_qs and .rcu_urgent_qs. Note that the |
|
* unsynchronized assignments to the per-CPU rcu_need_heavy_qs |
|
* variable are safe because the assignments are repeated if this |
|
* CPU failed to pass through a quiescent state. This code |
|
* also checks .jiffies_resched in case jiffies_to_sched_qs |
|
* is set way high. |
|
*/ |
|
jtsq = READ_ONCE(jiffies_to_sched_qs); |
|
ruqp = per_cpu_ptr(&rcu_data.rcu_urgent_qs, rdp->cpu); |
|
rnhqp = &per_cpu(rcu_data.rcu_need_heavy_qs, rdp->cpu); |
|
if (!READ_ONCE(*rnhqp) && |
|
(time_after(jiffies, rcu_state.gp_start + jtsq * 2) || |
|
time_after(jiffies, rcu_state.jiffies_resched) || |
|
rcu_state.cbovld)) { |
|
WRITE_ONCE(*rnhqp, true); |
|
/* Store rcu_need_heavy_qs before rcu_urgent_qs. */ |
|
smp_store_release(ruqp, true); |
|
} else if (time_after(jiffies, rcu_state.gp_start + jtsq)) { |
|
WRITE_ONCE(*ruqp, true); |
|
} |
|
|
|
/* |
|
* NO_HZ_FULL CPUs can run in-kernel without rcu_sched_clock_irq! |
|
* The above code handles this, but only for straight cond_resched(). |
|
* And some in-kernel loops check need_resched() before calling |
|
* cond_resched(), which defeats the above code for CPUs that are |
|
* running in-kernel with scheduling-clock interrupts disabled. |
|
* So hit them over the head with the resched_cpu() hammer! |
|
*/ |
|
if (tick_nohz_full_cpu(rdp->cpu) && |
|
(time_after(jiffies, READ_ONCE(rdp->last_fqs_resched) + jtsq * 3) || |
|
rcu_state.cbovld)) { |
|
WRITE_ONCE(*ruqp, true); |
|
resched_cpu(rdp->cpu); |
|
WRITE_ONCE(rdp->last_fqs_resched, jiffies); |
|
} |
|
|
|
/* |
|
* If more than halfway to RCU CPU stall-warning time, invoke |
|
* resched_cpu() more frequently to try to loosen things up a bit. |
|
* Also check to see if the CPU is getting hammered with interrupts, |
|
* but only once per grace period, just to keep the IPIs down to |
|
* a dull roar. |
|
*/ |
|
if (time_after(jiffies, rcu_state.jiffies_resched)) { |
|
if (time_after(jiffies, |
|
READ_ONCE(rdp->last_fqs_resched) + jtsq)) { |
|
resched_cpu(rdp->cpu); |
|
WRITE_ONCE(rdp->last_fqs_resched, jiffies); |
|
} |
|
if (IS_ENABLED(CONFIG_IRQ_WORK) && |
|
!rdp->rcu_iw_pending && rdp->rcu_iw_gp_seq != rnp->gp_seq && |
|
(rnp->ffmask & rdp->grpmask)) { |
|
rdp->rcu_iw_pending = true; |
|
rdp->rcu_iw_gp_seq = rnp->gp_seq; |
|
irq_work_queue_on(&rdp->rcu_iw, rdp->cpu); |
|
} |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
/* Trace-event wrapper function for trace_rcu_future_grace_period. */ |
|
static void trace_rcu_this_gp(struct rcu_node *rnp, struct rcu_data *rdp, |
|
unsigned long gp_seq_req, const char *s) |
|
{ |
|
trace_rcu_future_grace_period(rcu_state.name, READ_ONCE(rnp->gp_seq), |
|
gp_seq_req, rnp->level, |
|
rnp->grplo, rnp->grphi, s); |
|
} |
|
|
|
/* |
|
* rcu_start_this_gp - Request the start of a particular grace period |
|
* @rnp_start: The leaf node of the CPU from which to start. |
|
* @rdp: The rcu_data corresponding to the CPU from which to start. |
|
* @gp_seq_req: The gp_seq of the grace period to start. |
|
* |
|
* Start the specified grace period, as needed to handle newly arrived |
|
* callbacks. The required future grace periods are recorded in each |
|
* rcu_node structure's ->gp_seq_needed field. Returns true if there |
|
* is reason to awaken the grace-period kthread. |
|
* |
|
* The caller must hold the specified rcu_node structure's ->lock, which |
|
* is why the caller is responsible for waking the grace-period kthread. |
|
* |
|
* Returns true if the GP thread needs to be awakened else false. |
|
*/ |
|
static bool rcu_start_this_gp(struct rcu_node *rnp_start, struct rcu_data *rdp, |
|
unsigned long gp_seq_req) |
|
{ |
|
bool ret = false; |
|
struct rcu_node *rnp; |
|
|
|
/* |
|
* Use funnel locking to either acquire the root rcu_node |
|
* structure's lock or bail out if the need for this grace period |
|
* has already been recorded -- or if that grace period has in |
|
* fact already started. If there is already a grace period in |
|
* progress in a non-leaf node, no recording is needed because the |
|
* end of the grace period will scan the leaf rcu_node structures. |
|
* Note that rnp_start->lock must not be released. |
|
*/ |
|
raw_lockdep_assert_held_rcu_node(rnp_start); |
|
trace_rcu_this_gp(rnp_start, rdp, gp_seq_req, TPS("Startleaf")); |
|
for (rnp = rnp_start; 1; rnp = rnp->parent) { |
|
if (rnp != rnp_start) |
|
raw_spin_lock_rcu_node(rnp); |
|
if (ULONG_CMP_GE(rnp->gp_seq_needed, gp_seq_req) || |
|
rcu_seq_started(&rnp->gp_seq, gp_seq_req) || |
|
(rnp != rnp_start && |
|
rcu_seq_state(rcu_seq_current(&rnp->gp_seq)))) { |
|
trace_rcu_this_gp(rnp, rdp, gp_seq_req, |
|
TPS("Prestarted")); |
|
goto unlock_out; |
|
} |
|
WRITE_ONCE(rnp->gp_seq_needed, gp_seq_req); |
|
if (rcu_seq_state(rcu_seq_current(&rnp->gp_seq))) { |
|
/* |
|
* We just marked the leaf or internal node, and a |
|
* grace period is in progress, which means that |
|
* rcu_gp_cleanup() will see the marking. Bail to |
|
* reduce contention. |
|
*/ |
|
trace_rcu_this_gp(rnp_start, rdp, gp_seq_req, |
|
TPS("Startedleaf")); |
|
goto unlock_out; |
|
} |
|
if (rnp != rnp_start && rnp->parent != NULL) |
|
raw_spin_unlock_rcu_node(rnp); |
|
if (!rnp->parent) |
|
break; /* At root, and perhaps also leaf. */ |
|
} |
|
|
|
/* If GP already in progress, just leave, otherwise start one. */ |
|
if (rcu_gp_in_progress()) { |
|
trace_rcu_this_gp(rnp, rdp, gp_seq_req, TPS("Startedleafroot")); |
|
goto unlock_out; |
|
} |
|
trace_rcu_this_gp(rnp, rdp, gp_seq_req, TPS("Startedroot")); |
|
WRITE_ONCE(rcu_state.gp_flags, rcu_state.gp_flags | RCU_GP_FLAG_INIT); |
|
WRITE_ONCE(rcu_state.gp_req_activity, jiffies); |
|
if (!READ_ONCE(rcu_state.gp_kthread)) { |
|
trace_rcu_this_gp(rnp, rdp, gp_seq_req, TPS("NoGPkthread")); |
|
goto unlock_out; |
|
} |
|
trace_rcu_grace_period(rcu_state.name, data_race(rcu_state.gp_seq), TPS("newreq")); |
|
ret = true; /* Caller must wake GP kthread. */ |
|
unlock_out: |
|
/* Push furthest requested GP to leaf node and rcu_data structure. */ |
|
if (ULONG_CMP_LT(gp_seq_req, rnp->gp_seq_needed)) { |
|
WRITE_ONCE(rnp_start->gp_seq_needed, rnp->gp_seq_needed); |
|
WRITE_ONCE(rdp->gp_seq_needed, rnp->gp_seq_needed); |
|
} |
|
if (rnp != rnp_start) |
|
raw_spin_unlock_rcu_node(rnp); |
|
return ret; |
|
} |
|
|
|
/* |
|
* Clean up any old requests for the just-ended grace period. Also return |
|
* whether any additional grace periods have been requested. |
|
*/ |
|
static bool rcu_future_gp_cleanup(struct rcu_node *rnp) |
|
{ |
|
bool needmore; |
|
struct rcu_data *rdp = this_cpu_ptr(&rcu_data); |
|
|
|
needmore = ULONG_CMP_LT(rnp->gp_seq, rnp->gp_seq_needed); |
|
if (!needmore) |
|
rnp->gp_seq_needed = rnp->gp_seq; /* Avoid counter wrap. */ |
|
trace_rcu_this_gp(rnp, rdp, rnp->gp_seq, |
|
needmore ? TPS("CleanupMore") : TPS("Cleanup")); |
|
return needmore; |
|
} |
|
|
|
/* |
|
* Awaken the grace-period kthread. Don't do a self-awaken (unless in an |
|
* interrupt or softirq handler, in which case we just might immediately |
|
* sleep upon return, resulting in a grace-period hang), and don't bother |
|
* awakening when there is nothing for the grace-period kthread to do |
|
* (as in several CPUs raced to awaken, we lost), and finally don't try |
|
* to awaken a kthread that has not yet been created. If all those checks |
|
* are passed, track some debug information and awaken. |
|
* |
|
* So why do the self-wakeup when in an interrupt or softirq handler |
|
* in the grace-period kthread's context? Because the kthread might have |
|
* been interrupted just as it was going to sleep, and just after the final |
|
* pre-sleep check of the awaken condition. In this case, a wakeup really |
|
* is required, and is therefore supplied. |
|
*/ |
|
static void rcu_gp_kthread_wake(void) |
|
{ |
|
struct task_struct *t = READ_ONCE(rcu_state.gp_kthread); |
|
|
|
if ((current == t && !in_irq() && !in_serving_softirq()) || |
|
!READ_ONCE(rcu_state.gp_flags) || !t) |
|
return; |
|
WRITE_ONCE(rcu_state.gp_wake_time, jiffies); |
|
WRITE_ONCE(rcu_state.gp_wake_seq, READ_ONCE(rcu_state.gp_seq)); |
|
swake_up_one(&rcu_state.gp_wq); |
|
} |
|
|
|
/* |
|
* If there is room, assign a ->gp_seq number to any callbacks on this |
|
* CPU that have not already been assigned. Also accelerate any callbacks |
|
* that were previously assigned a ->gp_seq number that has since proven |
|
* to be too conservative, which can happen if callbacks get assigned a |
|
* ->gp_seq number while RCU is idle, but with reference to a non-root |
|
* rcu_node structure. This function is idempotent, so it does not hurt |
|
* to call it repeatedly. Returns an flag saying that we should awaken |
|
* the RCU grace-period kthread. |
|
* |
|
* The caller must hold rnp->lock with interrupts disabled. |
|
*/ |
|
static bool rcu_accelerate_cbs(struct rcu_node *rnp, struct rcu_data *rdp) |
|
{ |
|
unsigned long gp_seq_req; |
|
bool ret = false; |
|
|
|
rcu_lockdep_assert_cblist_protected(rdp); |
|
raw_lockdep_assert_held_rcu_node(rnp); |
|
|
|
/* If no pending (not yet ready to invoke) callbacks, nothing to do. */ |
|
if (!rcu_segcblist_pend_cbs(&rdp->cblist)) |
|
return false; |
|
|
|
trace_rcu_segcb_stats(&rdp->cblist, TPS("SegCbPreAcc")); |
|
|
|
/* |
|
* Callbacks are often registered with incomplete grace-period |
|
* information. Something about the fact that getting exact |
|
* information requires acquiring a global lock... RCU therefore |
|
* makes a conservative estimate of the grace period number at which |
|
* a given callback will become ready to invoke. The following |
|
* code checks this estimate and improves it when possible, thus |
|
* accelerating callback invocation to an earlier grace-period |
|
* number. |
|
*/ |
|
gp_seq_req = rcu_seq_snap(&rcu_state.gp_seq); |
|
if (rcu_segcblist_accelerate(&rdp->cblist, gp_seq_req)) |
|
ret = rcu_start_this_gp(rnp, rdp, gp_seq_req); |
|
|
|
/* Trace depending on how much we were able to accelerate. */ |
|
if (rcu_segcblist_restempty(&rdp->cblist, RCU_WAIT_TAIL)) |
|
trace_rcu_grace_period(rcu_state.name, gp_seq_req, TPS("AccWaitCB")); |
|
else |
|
trace_rcu_grace_period(rcu_state.name, gp_seq_req, TPS("AccReadyCB")); |
|
|
|
trace_rcu_segcb_stats(&rdp->cblist, TPS("SegCbPostAcc")); |
|
|
|
return ret; |
|
} |
|
|
|
/* |
|
* Similar to rcu_accelerate_cbs(), but does not require that the leaf |
|
* rcu_node structure's ->lock be held. It consults the cached value |
|
* of ->gp_seq_needed in the rcu_data structure, and if that indicates |
|
* that a new grace-period request be made, invokes rcu_accelerate_cbs() |
|
* while holding the leaf rcu_node structure's ->lock. |
|
*/ |
|
static void rcu_accelerate_cbs_unlocked(struct rcu_node *rnp, |
|
struct rcu_data *rdp) |
|
{ |
|
unsigned long c; |
|
bool needwake; |
|
|
|
rcu_lockdep_assert_cblist_protected(rdp); |
|
c = rcu_seq_snap(&rcu_state.gp_seq); |
|
if (!READ_ONCE(rdp->gpwrap) && ULONG_CMP_GE(rdp->gp_seq_needed, c)) { |
|
/* Old request still live, so mark recent callbacks. */ |
|
(void)rcu_segcblist_accelerate(&rdp->cblist, c); |
|
return; |
|
} |
|
raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */ |
|
needwake = rcu_accelerate_cbs(rnp, rdp); |
|
raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */ |
|
if (needwake) |
|
rcu_gp_kthread_wake(); |
|
} |
|
|
|
/* |
|
* Move any callbacks whose grace period has completed to the |
|
* RCU_DONE_TAIL sublist, then compact the remaining sublists and |
|
* assign ->gp_seq numbers to any callbacks in the RCU_NEXT_TAIL |
|
* sublist. This function is idempotent, so it does not hurt to |
|
* invoke it repeatedly. As long as it is not invoked -too- often... |
|
* Returns true if the RCU grace-period kthread needs to be awakened. |
|
* |
|
* The caller must hold rnp->lock with interrupts disabled. |
|
*/ |
|
static bool rcu_advance_cbs(struct rcu_node *rnp, struct rcu_data *rdp) |
|
{ |
|
rcu_lockdep_assert_cblist_protected(rdp); |
|
raw_lockdep_assert_held_rcu_node(rnp); |
|
|
|
/* If no pending (not yet ready to invoke) callbacks, nothing to do. */ |
|
if (!rcu_segcblist_pend_cbs(&rdp->cblist)) |
|
return false; |
|
|
|
/* |
|
* Find all callbacks whose ->gp_seq numbers indicate that they |
|
* are ready to invoke, and put them into the RCU_DONE_TAIL sublist. |
|
*/ |
|
rcu_segcblist_advance(&rdp->cblist, rnp->gp_seq); |
|
|
|
/* Classify any remaining callbacks. */ |
|
return rcu_accelerate_cbs(rnp, rdp); |
|
} |
|
|
|
/* |
|
* Move and classify callbacks, but only if doing so won't require |
|
* that the RCU grace-period kthread be awakened. |
|
*/ |
|
static void __maybe_unused rcu_advance_cbs_nowake(struct rcu_node *rnp, |
|
struct rcu_data *rdp) |
|
{ |
|
rcu_lockdep_assert_cblist_protected(rdp); |
|
if (!rcu_seq_state(rcu_seq_current(&rnp->gp_seq)) || |
|
!raw_spin_trylock_rcu_node(rnp)) |
|
return; |
|
WARN_ON_ONCE(rcu_advance_cbs(rnp, rdp)); |
|
raw_spin_unlock_rcu_node(rnp); |
|
} |
|
|
|
/* |
|
* In CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels, attempt to generate a |
|
* quiescent state. This is intended to be invoked when the CPU notices |
|
* a new grace period. |
|
*/ |
|
static void rcu_strict_gp_check_qs(void) |
|
{ |
|
if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD)) { |
|
rcu_read_lock(); |
|
rcu_read_unlock(); |
|
} |
|
} |
|
|
|
/* |
|
* Update CPU-local rcu_data state to record the beginnings and ends of |
|
* grace periods. The caller must hold the ->lock of the leaf rcu_node |
|
* structure corresponding to the current CPU, and must have irqs disabled. |
|
* Returns true if the grace-period kthread needs to be awakened. |
|
*/ |
|
static bool __note_gp_changes(struct rcu_node *rnp, struct rcu_data *rdp) |
|
{ |
|
bool ret = false; |
|
bool need_qs; |
|
const bool offloaded = rcu_segcblist_is_offloaded(&rdp->cblist); |
|
|
|
raw_lockdep_assert_held_rcu_node(rnp); |
|
|
|
if (rdp->gp_seq == rnp->gp_seq) |
|
return false; /* Nothing to do. */ |
|
|
|
/* Handle the ends of any preceding grace periods first. */ |
|
if (rcu_seq_completed_gp(rdp->gp_seq, rnp->gp_seq) || |
|
unlikely(READ_ONCE(rdp->gpwrap))) { |
|
if (!offloaded) |
|
ret = rcu_advance_cbs(rnp, rdp); /* Advance CBs. */ |
|
rdp->core_needs_qs = false; |
|
trace_rcu_grace_period(rcu_state.name, rdp->gp_seq, TPS("cpuend")); |
|
} else { |
|
if (!offloaded) |
|
ret = rcu_accelerate_cbs(rnp, rdp); /* Recent CBs. */ |
|
if (rdp->core_needs_qs) |
|
rdp->core_needs_qs = !!(rnp->qsmask & rdp->grpmask); |
|
} |
|
|
|
/* Now handle the beginnings of any new-to-this-CPU grace periods. */ |
|
if (rcu_seq_new_gp(rdp->gp_seq, rnp->gp_seq) || |
|
unlikely(READ_ONCE(rdp->gpwrap))) { |
|
/* |
|
* If the current grace period is waiting for this CPU, |
|
* set up to detect a quiescent state, otherwise don't |
|
* go looking for one. |
|
*/ |
|
trace_rcu_grace_period(rcu_state.name, rnp->gp_seq, TPS("cpustart")); |
|
need_qs = !!(rnp->qsmask & rdp->grpmask); |
|
rdp->cpu_no_qs.b.norm = need_qs; |
|
rdp->core_needs_qs = need_qs; |
|
zero_cpu_stall_ticks(rdp); |
|
} |
|
rdp->gp_seq = rnp->gp_seq; /* Remember new grace-period state. */ |
|
if (ULONG_CMP_LT(rdp->gp_seq_needed, rnp->gp_seq_needed) || rdp->gpwrap) |
|
WRITE_ONCE(rdp->gp_seq_needed, rnp->gp_seq_needed); |
|
WRITE_ONCE(rdp->gpwrap, false); |
|
rcu_gpnum_ovf(rnp, rdp); |
|
return ret; |
|
} |
|
|
|
static void note_gp_changes(struct rcu_data *rdp) |
|
{ |
|
unsigned long flags; |
|
bool needwake; |
|
struct rcu_node *rnp; |
|
|
|
local_irq_save(flags); |
|
rnp = rdp->mynode; |
|
if ((rdp->gp_seq == rcu_seq_current(&rnp->gp_seq) && |
|
!unlikely(READ_ONCE(rdp->gpwrap))) || /* w/out lock. */ |
|
!raw_spin_trylock_rcu_node(rnp)) { /* irqs already off, so later. */ |
|
local_irq_restore(flags); |
|
return; |
|
} |
|
needwake = __note_gp_changes(rnp, rdp); |
|
raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
|
rcu_strict_gp_check_qs(); |
|
if (needwake) |
|
rcu_gp_kthread_wake(); |
|
} |
|
|
|
static void rcu_gp_slow(int delay) |
|
{ |
|
if (delay > 0 && |
|
!(rcu_seq_ctr(rcu_state.gp_seq) % |
|
(rcu_num_nodes * PER_RCU_NODE_PERIOD * delay))) |
|
schedule_timeout_idle(delay); |
|
} |
|
|
|
static unsigned long sleep_duration; |
|
|
|
/* Allow rcutorture to stall the grace-period kthread. */ |
|
void rcu_gp_set_torture_wait(int duration) |
|
{ |
|
if (IS_ENABLED(CONFIG_RCU_TORTURE_TEST) && duration > 0) |
|
WRITE_ONCE(sleep_duration, duration); |
|
} |
|
EXPORT_SYMBOL_GPL(rcu_gp_set_torture_wait); |
|
|
|
/* Actually implement the aforementioned wait. */ |
|
static void rcu_gp_torture_wait(void) |
|
{ |
|
unsigned long duration; |
|
|
|
if (!IS_ENABLED(CONFIG_RCU_TORTURE_TEST)) |
|
return; |
|
duration = xchg(&sleep_duration, 0UL); |
|
if (duration > 0) { |
|
pr_alert("%s: Waiting %lu jiffies\n", __func__, duration); |
|
schedule_timeout_idle(duration); |
|
pr_alert("%s: Wait complete\n", __func__); |
|
} |
|
} |
|
|
|
/* |
|
* Handler for on_each_cpu() to invoke the target CPU's RCU core |
|
* processing. |
|
*/ |
|
static void rcu_strict_gp_boundary(void *unused) |
|
{ |
|
invoke_rcu_core(); |
|
} |
|
|
|
/* |
|
* Initialize a new grace period. Return false if no grace period required. |
|
*/ |
|
static bool rcu_gp_init(void) |
|
{ |
|
unsigned long firstseq; |
|
unsigned long flags; |
|
unsigned long oldmask; |
|
unsigned long mask; |
|
struct rcu_data *rdp; |
|
struct rcu_node *rnp = rcu_get_root(); |
|
|
|
WRITE_ONCE(rcu_state.gp_activity, jiffies); |
|
raw_spin_lock_irq_rcu_node(rnp); |
|
if (!READ_ONCE(rcu_state.gp_flags)) { |
|
/* Spurious wakeup, tell caller to go back to sleep. */ |
|
raw_spin_unlock_irq_rcu_node(rnp); |
|
return false; |
|
} |
|
WRITE_ONCE(rcu_state.gp_flags, 0); /* Clear all flags: New GP. */ |
|
|
|
if (WARN_ON_ONCE(rcu_gp_in_progress())) { |
|
/* |
|
* Grace period already in progress, don't start another. |
|
* Not supposed to be able to happen. |
|
*/ |
|
raw_spin_unlock_irq_rcu_node(rnp); |
|
return false; |
|
} |
|
|
|
/* Advance to a new grace period and initialize state. */ |
|
record_gp_stall_check_time(); |
|
/* Record GP times before starting GP, hence rcu_seq_start(). */ |
|
rcu_seq_start(&rcu_state.gp_seq); |
|
ASSERT_EXCLUSIVE_WRITER(rcu_state.gp_seq); |
|
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, TPS("start")); |
|
raw_spin_unlock_irq_rcu_node(rnp); |
|
|
|
/* |
|
* Apply per-leaf buffered online and offline operations to |
|
* the rcu_node tree. Note that this new grace period need not |
|
* wait for subsequent online CPUs, and that RCU hooks in the CPU |
|
* offlining path, when combined with checks in this function, |
|
* will handle CPUs that are currently going offline or that will |
|
* go offline later. Please also refer to "Hotplug CPU" section |
|
* of RCU's Requirements documentation. |
|
*/ |
|
WRITE_ONCE(rcu_state.gp_state, RCU_GP_ONOFF); |
|
rcu_for_each_leaf_node(rnp) { |
|
smp_mb(); // Pair with barriers used when updating ->ofl_seq to odd values. |
|
firstseq = READ_ONCE(rnp->ofl_seq); |
|
if (firstseq & 0x1) |
|
while (firstseq == READ_ONCE(rnp->ofl_seq)) |
|
schedule_timeout_idle(1); // Can't wake unless RCU is watching. |
|
smp_mb(); // Pair with barriers used when updating ->ofl_seq to even values. |
|
raw_spin_lock(&rcu_state.ofl_lock); |
|
raw_spin_lock_irq_rcu_node(rnp); |
|
if (rnp->qsmaskinit == rnp->qsmaskinitnext && |
|
!rnp->wait_blkd_tasks) { |
|
/* Nothing to do on this leaf rcu_node structure. */ |
|
raw_spin_unlock_irq_rcu_node(rnp); |
|
raw_spin_unlock(&rcu_state.ofl_lock); |
|
continue; |
|
} |
|
|
|
/* Record old state, apply changes to ->qsmaskinit field. */ |
|
oldmask = rnp->qsmaskinit; |
|
rnp->qsmaskinit = rnp->qsmaskinitnext; |
|
|
|
/* If zero-ness of ->qsmaskinit changed, propagate up tree. */ |
|
if (!oldmask != !rnp->qsmaskinit) { |
|
if (!oldmask) { /* First online CPU for rcu_node. */ |
|
if (!rnp->wait_blkd_tasks) /* Ever offline? */ |
|
rcu_init_new_rnp(rnp); |
|
} else if (rcu_preempt_has_tasks(rnp)) { |
|
rnp->wait_blkd_tasks = true; /* blocked tasks */ |
|
} else { /* Last offline CPU and can propagate. */ |
|
rcu_cleanup_dead_rnp(rnp); |
|
} |
|
} |
|
|
|
/* |
|
* If all waited-on tasks from prior grace period are |
|
* done, and if all this rcu_node structure's CPUs are |
|
* still offline, propagate up the rcu_node tree and |
|
* clear ->wait_blkd_tasks. Otherwise, if one of this |
|
* rcu_node structure's CPUs has since come back online, |
|
* simply clear ->wait_blkd_tasks. |
|
*/ |
|
if (rnp->wait_blkd_tasks && |
|
(!rcu_preempt_has_tasks(rnp) || rnp->qsmaskinit)) { |
|
rnp->wait_blkd_tasks = false; |
|
if (!rnp->qsmaskinit) |
|
rcu_cleanup_dead_rnp(rnp); |
|
} |
|
|
|
raw_spin_unlock_irq_rcu_node(rnp); |
|
raw_spin_unlock(&rcu_state.ofl_lock); |
|
} |
|
rcu_gp_slow(gp_preinit_delay); /* Races with CPU hotplug. */ |
|
|
|
/* |
|
* Set the quiescent-state-needed bits in all the rcu_node |
|
* structures for all currently online CPUs in breadth-first |
|
* order, starting from the root rcu_node structure, relying on the |
|
* layout of the tree within the rcu_state.node[] array. Note that |
|
* other CPUs will access only the leaves of the hierarchy, thus |
|
* seeing that no grace period is in progress, at least until the |
|
* corresponding leaf node has been initialized. |
|
* |
|
* The grace period cannot complete until the initialization |
|
* process finishes, because this kthread handles both. |
|
*/ |
|
WRITE_ONCE(rcu_state.gp_state, RCU_GP_INIT); |
|
rcu_for_each_node_breadth_first(rnp) { |
|
rcu_gp_slow(gp_init_delay); |
|
raw_spin_lock_irqsave_rcu_node(rnp, flags); |
|
rdp = this_cpu_ptr(&rcu_data); |
|
rcu_preempt_check_blocked_tasks(rnp); |
|
rnp->qsmask = rnp->qsmaskinit; |
|
WRITE_ONCE(rnp->gp_seq, rcu_state.gp_seq); |
|
if (rnp == rdp->mynode) |
|
(void)__note_gp_changes(rnp, rdp); |
|
rcu_preempt_boost_start_gp(rnp); |
|
trace_rcu_grace_period_init(rcu_state.name, rnp->gp_seq, |
|
rnp->level, rnp->grplo, |
|
rnp->grphi, rnp->qsmask); |
|
/* Quiescent states for tasks on any now-offline CPUs. */ |
|
mask = rnp->qsmask & ~rnp->qsmaskinitnext; |
|
rnp->rcu_gp_init_mask = mask; |
|
if ((mask || rnp->wait_blkd_tasks) && rcu_is_leaf_node(rnp)) |
|
rcu_report_qs_rnp(mask, rnp, rnp->gp_seq, flags); |
|
else |
|
raw_spin_unlock_irq_rcu_node(rnp); |
|
cond_resched_tasks_rcu_qs(); |
|
WRITE_ONCE(rcu_state.gp_activity, jiffies); |
|
} |
|
|
|
// If strict, make all CPUs aware of new grace period. |
|
if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD)) |
|
on_each_cpu(rcu_strict_gp_boundary, NULL, 0); |
|
|
|
return true; |
|
} |
|
|
|
/* |
|
* Helper function for swait_event_idle_exclusive() wakeup at force-quiescent-state |
|
* time. |
|
*/ |
|
static bool rcu_gp_fqs_check_wake(int *gfp) |
|
{ |
|
struct rcu_node *rnp = rcu_get_root(); |
|
|
|
// If under overload conditions, force an immediate FQS scan. |
|
if (*gfp & RCU_GP_FLAG_OVLD) |
|
return true; |
|
|
|
// Someone like call_rcu() requested a force-quiescent-state scan. |
|
*gfp = READ_ONCE(rcu_state.gp_flags); |
|
if (*gfp & RCU_GP_FLAG_FQS) |
|
return true; |
|
|
|
// The current grace period has completed. |
|
if (!READ_ONCE(rnp->qsmask) && !rcu_preempt_blocked_readers_cgp(rnp)) |
|
return true; |
|
|
|
return false; |
|
} |
|
|
|
/* |
|
* Do one round of quiescent-state forcing. |
|
*/ |
|
static void rcu_gp_fqs(bool first_time) |
|
{ |
|
struct rcu_node *rnp = rcu_get_root(); |
|
|
|
WRITE_ONCE(rcu_state.gp_activity, jiffies); |
|
rcu_state.n_force_qs++; |
|
if (first_time) { |
|
/* Collect dyntick-idle snapshots. */ |
|
force_qs_rnp(dyntick_save_progress_counter); |
|
} else { |
|
/* Handle dyntick-idle and offline CPUs. */ |
|
force_qs_rnp(rcu_implicit_dynticks_qs); |
|
} |
|
/* Clear flag to prevent immediate re-entry. */ |
|
if (READ_ONCE(rcu_state.gp_flags) & RCU_GP_FLAG_FQS) { |
|
raw_spin_lock_irq_rcu_node(rnp); |
|
WRITE_ONCE(rcu_state.gp_flags, |
|
READ_ONCE(rcu_state.gp_flags) & ~RCU_GP_FLAG_FQS); |
|
raw_spin_unlock_irq_rcu_node(rnp); |
|
} |
|
} |
|
|
|
/* |
|
* Loop doing repeated quiescent-state forcing until the grace period ends. |
|
*/ |
|
static void rcu_gp_fqs_loop(void) |
|
{ |
|
bool first_gp_fqs; |
|
int gf = 0; |
|
unsigned long j; |
|
int ret; |
|
struct rcu_node *rnp = rcu_get_root(); |
|
|
|
first_gp_fqs = true; |
|
j = READ_ONCE(jiffies_till_first_fqs); |
|
if (rcu_state.cbovld) |
|
gf = RCU_GP_FLAG_OVLD; |
|
ret = 0; |
|
for (;;) { |
|
if (!ret) { |
|
WRITE_ONCE(rcu_state.jiffies_force_qs, jiffies + j); |
|
/* |
|
* jiffies_force_qs before RCU_GP_WAIT_FQS state |
|
* update; required for stall checks. |
|
*/ |
|
smp_wmb(); |
|
WRITE_ONCE(rcu_state.jiffies_kick_kthreads, |
|
jiffies + (j ? 3 * j : 2)); |
|
} |
|
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, |
|
TPS("fqswait")); |
|
WRITE_ONCE(rcu_state.gp_state, RCU_GP_WAIT_FQS); |
|
ret = swait_event_idle_timeout_exclusive( |
|
rcu_state.gp_wq, rcu_gp_fqs_check_wake(&gf), j); |
|
rcu_gp_torture_wait(); |
|
WRITE_ONCE(rcu_state.gp_state, RCU_GP_DOING_FQS); |
|
/* Locking provides needed memory barriers. */ |
|
/* If grace period done, leave loop. */ |
|
if (!READ_ONCE(rnp->qsmask) && |
|
!rcu_preempt_blocked_readers_cgp(rnp)) |
|
break; |
|
/* If time for quiescent-state forcing, do it. */ |
|
if (!time_after(rcu_state.jiffies_force_qs, jiffies) || |
|
(gf & (RCU_GP_FLAG_FQS | RCU_GP_FLAG_OVLD))) { |
|
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, |
|
TPS("fqsstart")); |
|
rcu_gp_fqs(first_gp_fqs); |
|
gf = 0; |
|
if (first_gp_fqs) { |
|
first_gp_fqs = false; |
|
gf = rcu_state.cbovld ? RCU_GP_FLAG_OVLD : 0; |
|
} |
|
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, |
|
TPS("fqsend")); |
|
cond_resched_tasks_rcu_qs(); |
|
WRITE_ONCE(rcu_state.gp_activity, jiffies); |
|
ret = 0; /* Force full wait till next FQS. */ |
|
j = READ_ONCE(jiffies_till_next_fqs); |
|
} else { |
|
/* Deal with stray signal. */ |
|
cond_resched_tasks_rcu_qs(); |
|
WRITE_ONCE(rcu_state.gp_activity, jiffies); |
|
WARN_ON(signal_pending(current)); |
|
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, |
|
TPS("fqswaitsig")); |
|
ret = 1; /* Keep old FQS timing. */ |
|
j = jiffies; |
|
if (time_after(jiffies, rcu_state.jiffies_force_qs)) |
|
j = 1; |
|
else |
|
j = rcu_state.jiffies_force_qs - j; |
|
gf = 0; |
|
} |
|
} |
|
} |
|
|
|
/* |
|
* Clean up after the old grace period. |
|
*/ |
|
static void rcu_gp_cleanup(void) |
|
{ |
|
int cpu; |
|
bool needgp = false; |
|
unsigned long gp_duration; |
|
unsigned long new_gp_seq; |
|
bool offloaded; |
|
struct rcu_data *rdp; |
|
struct rcu_node *rnp = rcu_get_root(); |
|
struct swait_queue_head *sq; |
|
|
|
WRITE_ONCE(rcu_state.gp_activity, jiffies); |
|
raw_spin_lock_irq_rcu_node(rnp); |
|
rcu_state.gp_end = jiffies; |
|
gp_duration = rcu_state.gp_end - rcu_state.gp_start; |
|
if (gp_duration > rcu_state.gp_max) |
|
rcu_state.gp_max = gp_duration; |
|
|
|
/* |
|
* We know the grace period is complete, but to everyone else |
|
* it appears to still be ongoing. But it is also the case |
|
* that to everyone else it looks like there is nothing that |
|
* they can do to advance the grace period. It is therefore |
|
* safe for us to drop the lock in order to mark the grace |
|
* period as completed in all of the rcu_node structures. |
|
*/ |
|
raw_spin_unlock_irq_rcu_node(rnp); |
|
|
|
/* |
|
* Propagate new ->gp_seq value to rcu_node structures so that |
|
* other CPUs don't have to wait until the start of the next grace |
|
* period to process their callbacks. This also avoids some nasty |
|
* RCU grace-period initialization races by forcing the end of |
|
* the current grace period to be completely recorded in all of |
|
* the rcu_node structures before the beginning of the next grace |
|
* period is recorded in any of the rcu_node structures. |
|
*/ |
|
new_gp_seq = rcu_state.gp_seq; |
|
rcu_seq_end(&new_gp_seq); |
|
rcu_for_each_node_breadth_first(rnp) { |
|
raw_spin_lock_irq_rcu_node(rnp); |
|
if (WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp))) |
|
dump_blkd_tasks(rnp, 10); |
|
WARN_ON_ONCE(rnp->qsmask); |
|
WRITE_ONCE(rnp->gp_seq, new_gp_seq); |
|
rdp = this_cpu_ptr(&rcu_data); |
|
if (rnp == rdp->mynode) |
|
needgp = __note_gp_changes(rnp, rdp) || needgp; |
|
/* smp_mb() provided by prior unlock-lock pair. */ |
|
needgp = rcu_future_gp_cleanup(rnp) || needgp; |
|
// Reset overload indication for CPUs no longer overloaded |
|
if (rcu_is_leaf_node(rnp)) |
|
for_each_leaf_node_cpu_mask(rnp, cpu, rnp->cbovldmask) { |
|
rdp = per_cpu_ptr(&rcu_data, cpu); |
|
check_cb_ovld_locked(rdp, rnp); |
|
} |
|
sq = rcu_nocb_gp_get(rnp); |
|
raw_spin_unlock_irq_rcu_node(rnp); |
|
rcu_nocb_gp_cleanup(sq); |
|
cond_resched_tasks_rcu_qs(); |
|
WRITE_ONCE(rcu_state.gp_activity, jiffies); |
|
rcu_gp_slow(gp_cleanup_delay); |
|
} |
|
rnp = rcu_get_root(); |
|
raw_spin_lock_irq_rcu_node(rnp); /* GP before ->gp_seq update. */ |
|
|
|
/* Declare grace period done, trace first to use old GP number. */ |
|
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, TPS("end")); |
|
rcu_seq_end(&rcu_state.gp_seq); |
|
ASSERT_EXCLUSIVE_WRITER(rcu_state.gp_seq); |
|
WRITE_ONCE(rcu_state.gp_state, RCU_GP_IDLE); |
|
/* Check for GP requests since above loop. */ |
|
rdp = this_cpu_ptr(&rcu_data); |
|
if (!needgp && ULONG_CMP_LT(rnp->gp_seq, rnp->gp_seq_needed)) { |
|
trace_rcu_this_gp(rnp, rdp, rnp->gp_seq_needed, |
|
TPS("CleanupMore")); |
|
needgp = true; |
|
} |
|
/* Advance CBs to reduce false positives below. */ |
|
offloaded = rcu_segcblist_is_offloaded(&rdp->cblist); |
|
if ((offloaded || !rcu_accelerate_cbs(rnp, rdp)) && needgp) { |
|
WRITE_ONCE(rcu_state.gp_flags, RCU_GP_FLAG_INIT); |
|
WRITE_ONCE(rcu_state.gp_req_activity, jiffies); |
|
trace_rcu_grace_period(rcu_state.name, |
|
rcu_state.gp_seq, |
|
TPS("newreq")); |
|
} else { |
|
WRITE_ONCE(rcu_state.gp_flags, |
|
rcu_state.gp_flags & RCU_GP_FLAG_INIT); |
|
} |
|
raw_spin_unlock_irq_rcu_node(rnp); |
|
|
|
// If strict, make all CPUs aware of the end of the old grace period. |
|
if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD)) |
|
on_each_cpu(rcu_strict_gp_boundary, NULL, 0); |
|
} |
|
|
|
/* |
|
* Body of kthread that handles grace periods. |
|
*/ |
|
static int __noreturn rcu_gp_kthread(void *unused) |
|
{ |
|
rcu_bind_gp_kthread(); |
|
for (;;) { |
|
|
|
/* Handle grace-period start. */ |
|
for (;;) { |
|
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, |
|
TPS("reqwait")); |
|
WRITE_ONCE(rcu_state.gp_state, RCU_GP_WAIT_GPS); |
|
swait_event_idle_exclusive(rcu_state.gp_wq, |
|
READ_ONCE(rcu_state.gp_flags) & |
|
RCU_GP_FLAG_INIT); |
|
rcu_gp_torture_wait(); |
|
WRITE_ONCE(rcu_state.gp_state, RCU_GP_DONE_GPS); |
|
/* Locking provides needed memory barrier. */ |
|
if (rcu_gp_init()) |
|
break; |
|
cond_resched_tasks_rcu_qs(); |
|
WRITE_ONCE(rcu_state.gp_activity, jiffies); |
|
WARN_ON(signal_pending(current)); |
|
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, |
|
TPS("reqwaitsig")); |
|
} |
|
|
|
/* Handle quiescent-state forcing. */ |
|
rcu_gp_fqs_loop(); |
|
|
|
/* Handle grace-period end. */ |
|
WRITE_ONCE(rcu_state.gp_state, RCU_GP_CLEANUP); |
|
rcu_gp_cleanup(); |
|
WRITE_ONCE(rcu_state.gp_state, RCU_GP_CLEANED); |
|
} |
|
} |
|
|
|
/* |
|
* Report a full set of quiescent states to the rcu_state data structure. |
|
* Invoke rcu_gp_kthread_wake() to awaken the grace-period kthread if |
|
* another grace period is required. Whether we wake the grace-period |
|
* kthread or it awakens itself for the next round of quiescent-state |
|
* forcing, that kthread will clean up after the just-completed grace |
|
* period. Note that the caller must hold rnp->lock, which is released |
|
* before return. |
|
*/ |
|
static void rcu_report_qs_rsp(unsigned long flags) |
|
__releases(rcu_get_root()->lock) |
|
{ |
|
raw_lockdep_assert_held_rcu_node(rcu_get_root()); |
|
WARN_ON_ONCE(!rcu_gp_in_progress()); |
|
WRITE_ONCE(rcu_state.gp_flags, |
|
READ_ONCE(rcu_state.gp_flags) | RCU_GP_FLAG_FQS); |
|
raw_spin_unlock_irqrestore_rcu_node(rcu_get_root(), flags); |
|
rcu_gp_kthread_wake(); |
|
} |
|
|
|
/* |
|
* Similar to rcu_report_qs_rdp(), for which it is a helper function. |
|
* Allows quiescent states for a group of CPUs to be reported at one go |
|
* to the specified rcu_node structure, though all the CPUs in the group |
|
* must be represented by the same rcu_node structure (which need not be a |
|
* leaf rcu_node structure, though it often will be). The gps parameter |
|
* is the grace-period snapshot, which means that the quiescent states |
|
* are valid only if rnp->gp_seq is equal to gps. That structure's lock |
|
* must be held upon entry, and it is released before return. |
|
* |
|
* As a special case, if mask is zero, the bit-already-cleared check is |
|
* disabled. This allows propagating quiescent state due to resumed tasks |
|
* during grace-period initialization. |
|
*/ |
|
static void rcu_report_qs_rnp(unsigned long mask, struct rcu_node *rnp, |
|
unsigned long gps, unsigned long flags) |
|
__releases(rnp->lock) |
|
{ |
|
unsigned long oldmask = 0; |
|
struct rcu_node *rnp_c; |
|
|
|
raw_lockdep_assert_held_rcu_node(rnp); |
|
|
|
/* Walk up the rcu_node hierarchy. */ |
|
for (;;) { |
|
if ((!(rnp->qsmask & mask) && mask) || rnp->gp_seq != gps) { |
|
|
|
/* |
|
* Our bit has already been cleared, or the |
|
* relevant grace period is already over, so done. |
|
*/ |
|
raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
|
return; |
|
} |
|
WARN_ON_ONCE(oldmask); /* Any child must be all zeroed! */ |
|
WARN_ON_ONCE(!rcu_is_leaf_node(rnp) && |
|
rcu_preempt_blocked_readers_cgp(rnp)); |
|
WRITE_ONCE(rnp->qsmask, rnp->qsmask & ~mask); |
|
trace_rcu_quiescent_state_report(rcu_state.name, rnp->gp_seq, |
|
mask, rnp->qsmask, rnp->level, |
|
rnp->grplo, rnp->grphi, |
|
!!rnp->gp_tasks); |
|
if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) { |
|
|
|
/* Other bits still set at this level, so done. */ |
|
raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
|
return; |
|
} |
|
rnp->completedqs = rnp->gp_seq; |
|
mask = rnp->grpmask; |
|
if (rnp->parent == NULL) { |
|
|
|
/* No more levels. Exit loop holding root lock. */ |
|
|
|
break; |
|
} |
|
raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
|
rnp_c = rnp; |
|
rnp = rnp->parent; |
|
raw_spin_lock_irqsave_rcu_node(rnp, flags); |
|
oldmask = READ_ONCE(rnp_c->qsmask); |
|
} |
|
|
|
/* |
|
* Get here if we are the last CPU to pass through a quiescent |
|
* state for this grace period. Invoke rcu_report_qs_rsp() |
|
* to clean up and start the next grace period if one is needed. |
|
*/ |
|
rcu_report_qs_rsp(flags); /* releases rnp->lock. */ |
|
} |
|
|
|
/* |
|
* Record a quiescent state for all tasks that were previously queued |
|
* on the specified rcu_node structure and that were blocking the current |
|
* RCU grace period. The caller must hold the corresponding rnp->lock with |
|
* irqs disabled, and this lock is released upon return, but irqs remain |
|
* disabled. |
|
*/ |
|
static void __maybe_unused |
|
rcu_report_unblock_qs_rnp(struct rcu_node *rnp, unsigned long flags) |
|
__releases(rnp->lock) |
|
{ |
|
unsigned long gps; |
|
unsigned long mask; |
|
struct rcu_node *rnp_p; |
|
|
|
raw_lockdep_assert_held_rcu_node(rnp); |
|
if (WARN_ON_ONCE(!IS_ENABLED(CONFIG_PREEMPT_RCU)) || |
|
WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp)) || |
|
rnp->qsmask != 0) { |
|
raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
|
return; /* Still need more quiescent states! */ |
|
} |
|
|
|
rnp->completedqs = rnp->gp_seq; |
|
rnp_p = rnp->parent; |
|
if (rnp_p == NULL) { |
|
/* |
|
* Only one rcu_node structure in the tree, so don't |
|
* try to report up to its nonexistent parent! |
|
*/ |
|
rcu_report_qs_rsp(flags); |
|
return; |
|
} |
|
|
|
/* Report up the rest of the hierarchy, tracking current ->gp_seq. */ |
|
gps = rnp->gp_seq; |
|
mask = rnp->grpmask; |
|
raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */ |
|
raw_spin_lock_rcu_node(rnp_p); /* irqs already disabled. */ |
|
rcu_report_qs_rnp(mask, rnp_p, gps, flags); |
|
} |
|
|
|
/* |
|
* Record a quiescent state for the specified CPU to that CPU's rcu_data |
|
* structure. This must be called from the specified CPU. |
|
*/ |
|
static void |
|
rcu_report_qs_rdp(struct rcu_data *rdp) |
|
{ |
|
unsigned long flags; |
|
unsigned long mask; |
|
bool needwake = false; |
|
const bool offloaded = rcu_segcblist_is_offloaded(&rdp->cblist); |
|
struct rcu_node *rnp; |
|
|
|
WARN_ON_ONCE(rdp->cpu != smp_processor_id()); |
|
rnp = rdp->mynode; |
|
raw_spin_lock_irqsave_rcu_node(rnp, flags); |
|
if (rdp->cpu_no_qs.b.norm || rdp->gp_seq != rnp->gp_seq || |
|
rdp->gpwrap) { |
|
|
|
/* |
|
* The grace period in which this quiescent state was |
|
* recorded has ended, so don't report it upwards. |
|
* We will instead need a new quiescent state that lies |
|
* within the current grace period. |
|
*/ |
|
rdp->cpu_no_qs.b.norm = true; /* need qs for new gp. */ |
|
raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
|
return; |
|
} |
|
mask = rdp->grpmask; |
|
rdp->core_needs_qs = false; |
|
if ((rnp->qsmask & mask) == 0) { |
|
raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
|
} else { |
|
/* |
|
* This GP can't end until cpu checks in, so all of our |
|
* callbacks can be processed during the next GP. |
|
*/ |
|
if (!offloaded) |
|
needwake = rcu_accelerate_cbs(rnp, rdp); |
|
|
|
rcu_disable_urgency_upon_qs(rdp); |
|
rcu_report_qs_rnp(mask, rnp, rnp->gp_seq, flags); |
|
/* ^^^ Released rnp->lock */ |
|
if (needwake) |
|
rcu_gp_kthread_wake(); |
|
} |
|
} |
|
|
|
/* |
|
* Check to see if there is a new grace period of which this CPU |
|
* is not yet aware, and if so, set up local rcu_data state for it. |
|
* Otherwise, see if this CPU has just passed through its first |
|
* quiescent state for this grace period, and record that fact if so. |
|
*/ |
|
static void |
|
rcu_check_quiescent_state(struct rcu_data *rdp) |
|
{ |
|
/* Check for grace-period ends and beginnings. */ |
|
note_gp_changes(rdp); |
|
|
|
/* |
|
* Does this CPU still need to do its part for current grace period? |
|
* If no, return and let the other CPUs do their part as well. |
|
*/ |
|
if (!rdp->core_needs_qs) |
|
return; |
|
|
|
/* |
|
* Was there a quiescent state since the beginning of the grace |
|
* period? If no, then exit and wait for the next call. |
|
*/ |
|
if (rdp->cpu_no_qs.b.norm) |
|
return; |
|
|
|
/* |
|
* Tell RCU we are done (but rcu_report_qs_rdp() will be the |
|
* judge of that). |
|
*/ |
|
rcu_report_qs_rdp(rdp); |
|
} |
|
|
|
/* |
|
* Near the end of the offline process. Trace the fact that this CPU |
|
* is going offline. |
|
*/ |
|
int rcutree_dying_cpu(unsigned int cpu) |
|
{ |
|
bool blkd; |
|
struct rcu_data *rdp = this_cpu_ptr(&rcu_data); |
|
struct rcu_node *rnp = rdp->mynode; |
|
|
|
if (!IS_ENABLED(CONFIG_HOTPLUG_CPU)) |
|
return 0; |
|
|
|
blkd = !!(rnp->qsmask & rdp->grpmask); |
|
trace_rcu_grace_period(rcu_state.name, READ_ONCE(rnp->gp_seq), |
|
blkd ? TPS("cpuofl") : TPS("cpuofl-bgp")); |
|
return 0; |
|
} |
|
|
|
/* |
|
* All CPUs for the specified rcu_node structure have gone offline, |
|
* and all tasks that were preempted within an RCU read-side critical |
|
* section while running on one of those CPUs have since exited their RCU |
|
* read-side critical section. Some other CPU is reporting this fact with |
|
* the specified rcu_node structure's ->lock held and interrupts disabled. |
|
* This function therefore goes up the tree of rcu_node structures, |
|
* clearing the corresponding bits in the ->qsmaskinit fields. Note that |
|
* the leaf rcu_node structure's ->qsmaskinit field has already been |
|
* updated. |
|
* |
|
* This function does check that the specified rcu_node structure has |
|
* all CPUs offline and no blocked tasks, so it is OK to invoke it |
|
* prematurely. That said, invoking it after the fact will cost you |
|
* a needless lock acquisition. So once it has done its work, don't |
|
* invoke it again. |
|
*/ |
|
static void rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf) |
|
{ |
|
long mask; |
|
struct rcu_node *rnp = rnp_leaf; |
|
|
|
raw_lockdep_assert_held_rcu_node(rnp_leaf); |
|
if (!IS_ENABLED(CONFIG_HOTPLUG_CPU) || |
|
WARN_ON_ONCE(rnp_leaf->qsmaskinit) || |
|
WARN_ON_ONCE(rcu_preempt_has_tasks(rnp_leaf))) |
|
return; |
|
for (;;) { |
|
mask = rnp->grpmask; |
|
rnp = rnp->parent; |
|
if (!rnp) |
|
break; |
|
raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */ |
|
rnp->qsmaskinit &= ~mask; |
|
/* Between grace periods, so better already be zero! */ |
|
WARN_ON_ONCE(rnp->qsmask); |
|
if (rnp->qsmaskinit) { |
|
raw_spin_unlock_rcu_node(rnp); |
|
/* irqs remain disabled. */ |
|
return; |
|
} |
|
raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */ |
|
} |
|
} |
|
|
|
/* |
|
* The CPU has been completely removed, and some other CPU is reporting |
|
* this fact from process context. Do the remainder of the cleanup. |
|
* There can only be one CPU hotplug operation at a time, so no need for |
|
* explicit locking. |
|
*/ |
|
int rcutree_dead_cpu(unsigned int cpu) |
|
{ |
|
struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); |
|
struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */ |
|
|
|
if (!IS_ENABLED(CONFIG_HOTPLUG_CPU)) |
|
return 0; |
|
|
|
WRITE_ONCE(rcu_state.n_online_cpus, rcu_state.n_online_cpus - 1); |
|
/* Adjust any no-longer-needed kthreads. */ |
|
rcu_boost_kthread_setaffinity(rnp, -1); |
|
/* Do any needed no-CB deferred wakeups from this CPU. */ |
|
do_nocb_deferred_wakeup(per_cpu_ptr(&rcu_data, cpu)); |
|
|
|
// Stop-machine done, so allow nohz_full to disable tick. |
|
tick_dep_clear(TICK_DEP_BIT_RCU); |
|
return 0; |
|
} |
|
|
|
/* |
|
* Invoke any RCU callbacks that have made it to the end of their grace |
|
* period. Thottle as specified by rdp->blimit. |
|
*/ |
|
static void rcu_do_batch(struct rcu_data *rdp) |
|
{ |
|
int div; |
|
bool __maybe_unused empty; |
|
unsigned long flags; |
|
const bool offloaded = rcu_segcblist_is_offloaded(&rdp->cblist); |
|
struct rcu_head *rhp; |
|
struct rcu_cblist rcl = RCU_CBLIST_INITIALIZER(rcl); |
|
long bl, count = 0; |
|
long pending, tlimit = 0; |
|
|
|
/* If no callbacks are ready, just return. */ |
|
if (!rcu_segcblist_ready_cbs(&rdp->cblist)) { |
|
trace_rcu_batch_start(rcu_state.name, |
|
rcu_segcblist_n_cbs(&rdp->cblist), 0); |
|
trace_rcu_batch_end(rcu_state.name, 0, |
|
!rcu_segcblist_empty(&rdp->cblist), |
|
need_resched(), is_idle_task(current), |
|
rcu_is_callbacks_kthread()); |
|
return; |
|
} |
|
|
|
/* |
|
* Extract the list of ready callbacks, disabling to prevent |
|
* races with call_rcu() from interrupt handlers. Leave the |
|
* callback counts, as rcu_barrier() needs to be conservative. |
|
*/ |
|
local_irq_save(flags); |
|
rcu_nocb_lock(rdp); |
|
WARN_ON_ONCE(cpu_is_offline(smp_processor_id())); |
|
pending = rcu_segcblist_n_cbs(&rdp->cblist); |
|
div = READ_ONCE(rcu_divisor); |
|
div = div < 0 ? 7 : div > sizeof(long) * 8 - 2 ? sizeof(long) * 8 - 2 : div; |
|
bl = max(rdp->blimit, pending >> div); |
|
if (unlikely(bl > 100)) { |
|
long rrn = READ_ONCE(rcu_resched_ns); |
|
|
|
rrn = rrn < NSEC_PER_MSEC ? NSEC_PER_MSEC : rrn > NSEC_PER_SEC ? NSEC_PER_SEC : rrn; |
|
tlimit = local_clock() + rrn; |
|
} |
|
trace_rcu_batch_start(rcu_state.name, |
|
rcu_segcblist_n_cbs(&rdp->cblist), bl); |
|
rcu_segcblist_extract_done_cbs(&rdp->cblist, &rcl); |
|
if (offloaded) |
|
rdp->qlen_last_fqs_check = rcu_segcblist_n_cbs(&rdp->cblist); |
|
|
|
trace_rcu_segcb_stats(&rdp->cblist, TPS("SegCbDequeued")); |
|
rcu_nocb_unlock_irqrestore(rdp, flags); |
|
|
|
/* Invoke callbacks. */ |
|
tick_dep_set_task(current, TICK_DEP_BIT_RCU); |
|
rhp = rcu_cblist_dequeue(&rcl); |
|
|
|
for (; rhp; rhp = rcu_cblist_dequeue(&rcl)) { |
|
rcu_callback_t f; |
|
|
|
count++; |
|
debug_rcu_head_unqueue(rhp); |
|
|
|
rcu_lock_acquire(&rcu_callback_map); |
|
trace_rcu_invoke_callback(rcu_state.name, rhp); |
|
|
|
f = rhp->func; |
|
WRITE_ONCE(rhp->func, (rcu_callback_t)0L); |
|
f(rhp); |
|
|
|
rcu_lock_release(&rcu_callback_map); |
|
|
|
/* |
|
* Stop only if limit reached and CPU has something to do. |
|
*/ |
|
if (count >= bl && !offloaded && |
|
(need_resched() || |
|
(!is_idle_task(current) && !rcu_is_callbacks_kthread()))) |
|
break; |
|
if (unlikely(tlimit)) { |
|
/* only call local_clock() every 32 callbacks */ |
|
if (likely((count & 31) || local_clock() < tlimit)) |
|
continue; |
|
/* Exceeded the time limit, so leave. */ |
|
break; |
|
} |
|
if (!in_serving_softirq()) { |
|
local_bh_enable(); |
|
lockdep_assert_irqs_enabled(); |
|
cond_resched_tasks_rcu_qs(); |
|
lockdep_assert_irqs_enabled(); |
|
local_bh_disable(); |
|
} |
|
} |
|
|
|
local_irq_save(flags); |
|
rcu_nocb_lock(rdp); |
|
rdp->n_cbs_invoked += count; |
|
trace_rcu_batch_end(rcu_state.name, count, !!rcl.head, need_resched(), |
|
is_idle_task(current), rcu_is_callbacks_kthread()); |
|
|
|
/* Update counts and requeue any remaining callbacks. */ |
|
rcu_segcblist_insert_done_cbs(&rdp->cblist, &rcl); |
|
rcu_segcblist_add_len(&rdp->cblist, -count); |
|
|
|
/* Reinstate batch limit if we have worked down the excess. */ |
|
count = rcu_segcblist_n_cbs(&rdp->cblist); |
|
if (rdp->blimit >= DEFAULT_MAX_RCU_BLIMIT && count <= qlowmark) |
|
rdp->blimit = blimit; |
|
|
|
/* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */ |
|
if (count == 0 && rdp->qlen_last_fqs_check != 0) { |
|
rdp->qlen_last_fqs_check = 0; |
|
rdp->n_force_qs_snap = rcu_state.n_force_qs; |
|
} else if (count < rdp->qlen_last_fqs_check - qhimark) |
|
rdp->qlen_last_fqs_check = count; |
|
|
|
/* |
|
* The following usually indicates a double call_rcu(). To track |
|
* this down, try building with CONFIG_DEBUG_OBJECTS_RCU_HEAD=y. |
|
*/ |
|
empty = rcu_segcblist_empty(&rdp->cblist); |
|
WARN_ON_ONCE(count == 0 && !empty); |
|
WARN_ON_ONCE(!IS_ENABLED(CONFIG_RCU_NOCB_CPU) && |
|
count != 0 && empty); |
|
WARN_ON_ONCE(count == 0 && rcu_segcblist_n_segment_cbs(&rdp->cblist) != 0); |
|
WARN_ON_ONCE(!empty && rcu_segcblist_n_segment_cbs(&rdp->cblist) == 0); |
|
|
|
rcu_nocb_unlock_irqrestore(rdp, flags); |
|
|
|
/* Re-invoke RCU core processing if there are callbacks remaining. */ |
|
if (!offloaded && rcu_segcblist_ready_cbs(&rdp->cblist)) |
|
invoke_rcu_core(); |
|
tick_dep_clear_task(current, TICK_DEP_BIT_RCU); |
|
} |
|
|
|
/* |
|
* This function is invoked from each scheduling-clock interrupt, |
|
* and checks to see if this CPU is in a non-context-switch quiescent |
|
* state, for example, user mode or idle loop. It also schedules RCU |
|
* core processing. If the current grace period has gone on too long, |
|
* it will ask the scheduler to manufacture a context switch for the sole |
|
* purpose of providing a providing the needed quiescent state. |
|
*/ |
|
void rcu_sched_clock_irq(int user) |
|
{ |
|
trace_rcu_utilization(TPS("Start scheduler-tick")); |
|
lockdep_assert_irqs_disabled(); |
|
raw_cpu_inc(rcu_data.ticks_this_gp); |
|
/* The load-acquire pairs with the store-release setting to true. */ |
|
if (smp_load_acquire(this_cpu_ptr(&rcu_data.rcu_urgent_qs))) { |
|
/* Idle and userspace execution already are quiescent states. */ |
|
if (!rcu_is_cpu_rrupt_from_idle() && !user) { |
|
set_tsk_need_resched(current); |
|
set_preempt_need_resched(); |
|
} |
|
__this_cpu_write(rcu_data.rcu_urgent_qs, false); |
|
} |
|
rcu_flavor_sched_clock_irq(user); |
|
if (rcu_pending(user)) |
|
invoke_rcu_core(); |
|
lockdep_assert_irqs_disabled(); |
|
|
|
trace_rcu_utilization(TPS("End scheduler-tick")); |
|
} |
|
|
|
/* |
|
* Scan the leaf rcu_node structures. For each structure on which all |
|
* CPUs have reported a quiescent state and on which there are tasks |
|
* blocking the current grace period, initiate RCU priority boosting. |
|
* Otherwise, invoke the specified function to check dyntick state for |
|
* each CPU that has not yet reported a quiescent state. |
|
*/ |
|
static void force_qs_rnp(int (*f)(struct rcu_data *rdp)) |
|
{ |
|
int cpu; |
|
unsigned long flags; |
|
unsigned long mask; |
|
struct rcu_data *rdp; |
|
struct rcu_node *rnp; |
|
|
|
rcu_state.cbovld = rcu_state.cbovldnext; |
|
rcu_state.cbovldnext = false; |
|
rcu_for_each_leaf_node(rnp) { |
|
cond_resched_tasks_rcu_qs(); |
|
mask = 0; |
|
raw_spin_lock_irqsave_rcu_node(rnp, flags); |
|
rcu_state.cbovldnext |= !!rnp->cbovldmask; |
|
if (rnp->qsmask == 0) { |
|
if (rcu_preempt_blocked_readers_cgp(rnp)) { |
|
/* |
|
* No point in scanning bits because they |
|
* are all zero. But we might need to |
|
* priority-boost blocked readers. |
|
*/ |
|
rcu_initiate_boost(rnp, flags); |
|
/* rcu_initiate_boost() releases rnp->lock */ |
|
continue; |
|
} |
|
raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
|
continue; |
|
} |
|
for_each_leaf_node_cpu_mask(rnp, cpu, rnp->qsmask) { |
|
rdp = per_cpu_ptr(&rcu_data, cpu); |
|
if (f(rdp)) { |
|
mask |= rdp->grpmask; |
|
rcu_disable_urgency_upon_qs(rdp); |
|
} |
|
} |
|
if (mask != 0) { |
|
/* Idle/offline CPUs, report (releases rnp->lock). */ |
|
rcu_report_qs_rnp(mask, rnp, rnp->gp_seq, flags); |
|
} else { |
|
/* Nothing to do here, so just drop the lock. */ |
|
raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
|
} |
|
} |
|
} |
|
|
|
/* |
|
* Force quiescent states on reluctant CPUs, and also detect which |
|
* CPUs are in dyntick-idle mode. |
|
*/ |
|
void rcu_force_quiescent_state(void) |
|
{ |
|
unsigned long flags; |
|
bool ret; |
|
struct rcu_node *rnp; |
|
struct rcu_node *rnp_old = NULL; |
|
|
|
/* Funnel through hierarchy to reduce memory contention. */ |
|
rnp = __this_cpu_read(rcu_data.mynode); |
|
for (; rnp != NULL; rnp = rnp->parent) { |
|
ret = (READ_ONCE(rcu_state.gp_flags) & RCU_GP_FLAG_FQS) || |
|
!raw_spin_trylock(&rnp->fqslock); |
|
if (rnp_old != NULL) |
|
raw_spin_unlock(&rnp_old->fqslock); |
|
if (ret) |
|
return; |
|
rnp_old = rnp; |
|
} |
|
/* rnp_old == rcu_get_root(), rnp == NULL. */ |
|
|
|
/* Reached the root of the rcu_node tree, acquire lock. */ |
|
raw_spin_lock_irqsave_rcu_node(rnp_old, flags); |
|
raw_spin_unlock(&rnp_old->fqslock); |
|
if (READ_ONCE(rcu_state.gp_flags) & RCU_GP_FLAG_FQS) { |
|
raw_spin_unlock_irqrestore_rcu_node(rnp_old, flags); |
|
return; /* Someone beat us to it. */ |
|
} |
|
WRITE_ONCE(rcu_state.gp_flags, |
|
READ_ONCE(rcu_state.gp_flags) | RCU_GP_FLAG_FQS); |
|
raw_spin_unlock_irqrestore_rcu_node(rnp_old, flags); |
|
rcu_gp_kthread_wake(); |
|
} |
|
EXPORT_SYMBOL_GPL(rcu_force_quiescent_state); |
|
|
|
// Workqueue handler for an RCU reader for kernels enforcing struct RCU |
|
// grace periods. |
|
static void strict_work_handler(struct work_struct *work) |
|
{ |
|
rcu_read_lock(); |
|
rcu_read_unlock(); |
|
} |
|
|
|
/* Perform RCU core processing work for the current CPU. */ |
|
static __latent_entropy void rcu_core(void) |
|
{ |
|
unsigned long flags; |
|
struct rcu_data *rdp = raw_cpu_ptr(&rcu_data); |
|
struct rcu_node *rnp = rdp->mynode; |
|
const bool do_batch = !rcu_segcblist_completely_offloaded(&rdp->cblist); |
|
|
|
if (cpu_is_offline(smp_processor_id())) |
|
return; |
|
trace_rcu_utilization(TPS("Start RCU core")); |
|
WARN_ON_ONCE(!rdp->beenonline); |
|
|
|
/* Report any deferred quiescent states if preemption enabled. */ |
|
if (!(preempt_count() & PREEMPT_MASK)) { |
|
rcu_preempt_deferred_qs(current); |
|
} else if (rcu_preempt_need_deferred_qs(current)) { |
|
set_tsk_need_resched(current); |
|
set_preempt_need_resched(); |
|
} |
|
|
|
/* Update RCU state based on any recent quiescent states. */ |
|
rcu_check_quiescent_state(rdp); |
|
|
|
/* No grace period and unregistered callbacks? */ |
|
if (!rcu_gp_in_progress() && |
|
rcu_segcblist_is_enabled(&rdp->cblist) && do_batch) { |
|
rcu_nocb_lock_irqsave(rdp, flags); |
|
if (!rcu_segcblist_restempty(&rdp->cblist, RCU_NEXT_READY_TAIL)) |
|
rcu_accelerate_cbs_unlocked(rnp, rdp); |
|
rcu_nocb_unlock_irqrestore(rdp, flags); |
|
} |
|
|
|
rcu_check_gp_start_stall(rnp, rdp, rcu_jiffies_till_stall_check()); |
|
|
|
/* If there are callbacks ready, invoke them. */ |
|
if (do_batch && rcu_segcblist_ready_cbs(&rdp->cblist) && |
|
likely(READ_ONCE(rcu_scheduler_fully_active))) |
|
rcu_do_batch(rdp); |
|
|
|
/* Do any needed deferred wakeups of rcuo kthreads. */ |
|
do_nocb_deferred_wakeup(rdp); |
|
trace_rcu_utilization(TPS("End RCU core")); |
|
|
|
// If strict GPs, schedule an RCU reader in a clean environment. |
|
if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD)) |
|
queue_work_on(rdp->cpu, rcu_gp_wq, &rdp->strict_work); |
|
} |
|
|
|
static void rcu_core_si(struct softirq_action *h) |
|
{ |
|
rcu_core(); |
|
} |
|
|
|
static void rcu_wake_cond(struct task_struct *t, int status) |
|
{ |
|
/* |
|
* If the thread is yielding, only wake it when this |
|
* is invoked from idle |
|
*/ |
|
if (t && (status != RCU_KTHREAD_YIELDING || is_idle_task(current))) |
|
wake_up_process(t); |
|
} |
|
|
|
static void invoke_rcu_core_kthread(void) |
|
{ |
|
struct task_struct *t; |
|
unsigned long flags; |
|
|
|
local_irq_save(flags); |
|
__this_cpu_write(rcu_data.rcu_cpu_has_work, 1); |
|
t = __this_cpu_read(rcu_data.rcu_cpu_kthread_task); |
|
if (t != NULL && t != current) |
|
rcu_wake_cond(t, __this_cpu_read(rcu_data.rcu_cpu_kthread_status)); |
|
local_irq_restore(flags); |
|
} |
|
|
|
/* |
|
* Wake up this CPU's rcuc kthread to do RCU core processing. |
|
*/ |
|
static void invoke_rcu_core(void) |
|
{ |
|
if (!cpu_online(smp_processor_id())) |
|
return; |
|
if (use_softirq) |
|
raise_softirq(RCU_SOFTIRQ); |
|
else |
|
invoke_rcu_core_kthread(); |
|
} |
|
|
|
static void rcu_cpu_kthread_park(unsigned int cpu) |
|
{ |
|
per_cpu(rcu_data.rcu_cpu_kthread_status, cpu) = RCU_KTHREAD_OFFCPU; |
|
} |
|
|
|
static int rcu_cpu_kthread_should_run(unsigned int cpu) |
|
{ |
|
return __this_cpu_read(rcu_data.rcu_cpu_has_work); |
|
} |
|
|
|
/* |
|
* Per-CPU kernel thread that invokes RCU callbacks. This replaces |
|
* the RCU softirq used in configurations of RCU that do not support RCU |
|
* priority boosting. |
|
*/ |
|
static void rcu_cpu_kthread(unsigned int cpu) |
|
{ |
|
unsigned int *statusp = this_cpu_ptr(&rcu_data.rcu_cpu_kthread_status); |
|
char work, *workp = this_cpu_ptr(&rcu_data.rcu_cpu_has_work); |
|
int spincnt; |
|
|
|
trace_rcu_utilization(TPS("Start CPU kthread@rcu_run")); |
|
for (spincnt = 0; spincnt < 10; spincnt++) { |
|
local_bh_disable(); |
|
*statusp = RCU_KTHREAD_RUNNING; |
|
local_irq_disable(); |
|
work = *workp; |
|
*workp = 0; |
|
local_irq_enable(); |
|
if (work) |
|
rcu_core(); |
|
local_bh_enable(); |
|
if (*workp == 0) { |
|
trace_rcu_utilization(TPS("End CPU kthread@rcu_wait")); |
|
*statusp = RCU_KTHREAD_WAITING; |
|
return; |
|
} |
|
} |
|
*statusp = RCU_KTHREAD_YIELDING; |
|
trace_rcu_utilization(TPS("Start CPU kthread@rcu_yield")); |
|
schedule_timeout_idle(2); |
|
trace_rcu_utilization(TPS("End CPU kthread@rcu_yield")); |
|
*statusp = RCU_KTHREAD_WAITING; |
|
} |
|
|
|
static struct smp_hotplug_thread rcu_cpu_thread_spec = { |
|
.store = &rcu_data.rcu_cpu_kthread_task, |
|
.thread_should_run = rcu_cpu_kthread_should_run, |
|
.thread_fn = rcu_cpu_kthread, |
|
.thread_comm = "rcuc/%u", |
|
.setup = rcu_cpu_kthread_setup, |
|
.park = rcu_cpu_kthread_park, |
|
}; |
|
|
|
/* |
|
* Spawn per-CPU RCU core processing kthreads. |
|
*/ |
|
static int __init rcu_spawn_core_kthreads(void) |
|
{ |
|
int cpu; |
|
|
|
for_each_possible_cpu(cpu) |
|
per_cpu(rcu_data.rcu_cpu_has_work, cpu) = 0; |
|
if (!IS_ENABLED(CONFIG_RCU_BOOST) && use_softirq) |
|
return 0; |
|
WARN_ONCE(smpboot_register_percpu_thread(&rcu_cpu_thread_spec), |
|
"%s: Could not start rcuc kthread, OOM is now expected behavior\n", __func__); |
|
return 0; |
|
} |
|
early_initcall(rcu_spawn_core_kthreads); |
|
|
|
/* |
|
* Handle any core-RCU processing required by a call_rcu() invocation. |
|
*/ |
|
static void __call_rcu_core(struct rcu_data *rdp, struct rcu_head *head, |
|
unsigned long flags) |
|
{ |
|
/* |
|
* If called from an extended quiescent state, invoke the RCU |
|
* core in order to force a re-evaluation of RCU's idleness. |
|
*/ |
|
if (!rcu_is_watching()) |
|
invoke_rcu_core(); |
|
|
|
/* If interrupts were disabled or CPU offline, don't invoke RCU core. */ |
|
if (irqs_disabled_flags(flags) || cpu_is_offline(smp_processor_id())) |
|
return; |
|
|
|
/* |
|
* Force the grace period if too many callbacks or too long waiting. |
|
* Enforce hysteresis, and don't invoke rcu_force_quiescent_state() |
|
* if some other CPU has recently done so. Also, don't bother |
|
* invoking rcu_force_quiescent_state() if the newly enqueued callback |
|
* is the only one waiting for a grace period to complete. |
|
*/ |
|
if (unlikely(rcu_segcblist_n_cbs(&rdp->cblist) > |
|
rdp->qlen_last_fqs_check + qhimark)) { |
|
|
|
/* Are we ignoring a completed grace period? */ |
|
note_gp_changes(rdp); |
|
|
|
/* Start a new grace period if one not already started. */ |
|
if (!rcu_gp_in_progress()) { |
|
rcu_accelerate_cbs_unlocked(rdp->mynode, rdp); |
|
} else { |
|
/* Give the grace period a kick. */ |
|
rdp->blimit = DEFAULT_MAX_RCU_BLIMIT; |
|
if (rcu_state.n_force_qs == rdp->n_force_qs_snap && |
|
rcu_segcblist_first_pend_cb(&rdp->cblist) != head) |
|
rcu_force_quiescent_state(); |
|
rdp->n_force_qs_snap = rcu_state.n_force_qs; |
|
rdp->qlen_last_fqs_check = rcu_segcblist_n_cbs(&rdp->cblist); |
|
} |
|
} |
|
} |
|
|
|
/* |
|
* RCU callback function to leak a callback. |
|
*/ |
|
static void rcu_leak_callback(struct rcu_head *rhp) |
|
{ |
|
} |
|
|
|
/* |
|
* Check and if necessary update the leaf rcu_node structure's |
|
* ->cbovldmask bit corresponding to the current CPU based on that CPU's |
|
* number of queued RCU callbacks. The caller must hold the leaf rcu_node |
|
* structure's ->lock. |
|
*/ |
|
static void check_cb_ovld_locked(struct rcu_data *rdp, struct rcu_node *rnp) |
|
{ |
|
raw_lockdep_assert_held_rcu_node(rnp); |
|
if (qovld_calc <= 0) |
|
return; // Early boot and wildcard value set. |
|
if (rcu_segcblist_n_cbs(&rdp->cblist) >= qovld_calc) |
|
WRITE_ONCE(rnp->cbovldmask, rnp->cbovldmask | rdp->grpmask); |
|
else |
|
WRITE_ONCE(rnp->cbovldmask, rnp->cbovldmask & ~rdp->grpmask); |
|
} |
|
|
|
/* |
|
* Check and if necessary update the leaf rcu_node structure's |
|
* ->cbovldmask bit corresponding to the current CPU based on that CPU's |
|
* number of queued RCU callbacks. No locks need be held, but the |
|
* caller must have disabled interrupts. |
|
* |
|
* Note that this function ignores the possibility that there are a lot |
|
* of callbacks all of which have already seen the end of their respective |
|
* grace periods. This omission is due to the need for no-CBs CPUs to |
|
* be holding ->nocb_lock to do this check, which is too heavy for a |
|
* common-case operation. |
|
*/ |
|
static void check_cb_ovld(struct rcu_data *rdp) |
|
{ |
|
struct rcu_node *const rnp = rdp->mynode; |
|
|
|
if (qovld_calc <= 0 || |
|
((rcu_segcblist_n_cbs(&rdp->cblist) >= qovld_calc) == |
|
!!(READ_ONCE(rnp->cbovldmask) & rdp->grpmask))) |
|
return; // Early boot wildcard value or already set correctly. |
|
raw_spin_lock_rcu_node(rnp); |
|
check_cb_ovld_locked(rdp, rnp); |
|
raw_spin_unlock_rcu_node(rnp); |
|
} |
|
|
|
/* Helper function for call_rcu() and friends. */ |
|
static void |
|
__call_rcu(struct rcu_head *head, rcu_callback_t func) |
|
{ |
|
static atomic_t doublefrees; |
|
unsigned long flags; |
|
struct rcu_data *rdp; |
|
bool was_alldone; |
|
|
|
/* Misaligned rcu_head! */ |
|
WARN_ON_ONCE((unsigned long)head & (sizeof(void *) - 1)); |
|
|
|
if (debug_rcu_head_queue(head)) { |
|
/* |
|
* Probable double call_rcu(), so leak the callback. |
|
* Use rcu:rcu_callback trace event to find the previous |
|
* time callback was passed to __call_rcu(). |
|
*/ |
|
if (atomic_inc_return(&doublefrees) < 4) { |
|
pr_err("%s(): Double-freed CB %p->%pS()!!! ", __func__, head, head->func); |
|
mem_dump_obj(head); |
|
} |
|
WRITE_ONCE(head->func, rcu_leak_callback); |
|
return; |
|
} |
|
head->func = func; |
|
head->next = NULL; |
|
local_irq_save(flags); |
|
kasan_record_aux_stack(head); |
|
rdp = this_cpu_ptr(&rcu_data); |
|
|
|
/* Add the callback to our list. */ |
|
if (unlikely(!rcu_segcblist_is_enabled(&rdp->cblist))) { |
|
// This can trigger due to call_rcu() from offline CPU: |
|
WARN_ON_ONCE(rcu_scheduler_active != RCU_SCHEDULER_INACTIVE); |
|
WARN_ON_ONCE(!rcu_is_watching()); |
|
// Very early boot, before rcu_init(). Initialize if needed |
|
// and then drop through to queue the callback. |
|
if (rcu_segcblist_empty(&rdp->cblist)) |
|
rcu_segcblist_init(&rdp->cblist); |
|
} |
|
|
|
check_cb_ovld(rdp); |
|
if (rcu_nocb_try_bypass(rdp, head, &was_alldone, flags)) |
|
return; // Enqueued onto ->nocb_bypass, so just leave. |
|
// If no-CBs CPU gets here, rcu_nocb_try_bypass() acquired ->nocb_lock. |
|
rcu_segcblist_enqueue(&rdp->cblist, head); |
|
if (__is_kvfree_rcu_offset((unsigned long)func)) |
|
trace_rcu_kvfree_callback(rcu_state.name, head, |
|
(unsigned long)func, |
|
rcu_segcblist_n_cbs(&rdp->cblist)); |
|
else |
|
trace_rcu_callback(rcu_state.name, head, |
|
rcu_segcblist_n_cbs(&rdp->cblist)); |
|
|
|
trace_rcu_segcb_stats(&rdp->cblist, TPS("SegCBQueued")); |
|
|
|
/* Go handle any RCU core processing required. */ |
|
if (unlikely(rcu_segcblist_is_offloaded(&rdp->cblist))) { |
|
__call_rcu_nocb_wake(rdp, was_alldone, flags); /* unlocks */ |
|
} else { |
|
__call_rcu_core(rdp, head, flags); |
|
local_irq_restore(flags); |
|
} |
|
} |
|
|
|
/** |
|
* call_rcu() - Queue an RCU callback for invocation after a grace period. |
|
* @head: structure to be used for queueing the RCU updates. |
|
* @func: actual callback function to be invoked after the grace period |
|
* |
|
* The callback function will be invoked some time after a full grace |
|
* period elapses, in other words after all pre-existing RCU read-side |
|
* critical sections have completed. However, the callback function |
|
* might well execute concurrently with RCU read-side critical sections |
|
* that started after call_rcu() was invoked. RCU read-side critical |
|
* sections are delimited by rcu_read_lock() and rcu_read_unlock(), and |
|
* may be nested. In addition, regions of code across which interrupts, |
|
* preemption, or softirqs have been disabled also serve as RCU read-side |
|
* critical sections. This includes hardware interrupt handlers, softirq |
|
* handlers, and NMI handlers. |
|
* |
|
* Note that all CPUs must agree that the grace period extended beyond |
|
* all pre-existing RCU read-side critical section. On systems with more |
|
* than one CPU, this means that when "func()" is invoked, each CPU is |
|
* guaranteed to have executed a full memory barrier since the end of its |
|
* last RCU read-side critical section whose beginning preceded the call |
|
* to call_rcu(). It also means that each CPU executing an RCU read-side |
|
* critical section that continues beyond the start of "func()" must have |
|
* executed a memory barrier after the call_rcu() but before the beginning |
|
* of that RCU read-side critical section. Note that these guarantees |
|
* include CPUs that are offline, idle, or executing in user mode, as |
|
* well as CPUs that are executing in the kernel. |
|
* |
|
* Furthermore, if CPU A invoked call_rcu() and CPU B invoked the |
|
* resulting RCU callback function "func()", then both CPU A and CPU B are |
|
* guaranteed to execute a full memory barrier during the time interval |
|
* between the call to call_rcu() and the invocation of "func()" -- even |
|
* if CPU A and CPU B are the same CPU (but again only if the system has |
|
* more than one CPU). |
|
*/ |
|
void call_rcu(struct rcu_head *head, rcu_callback_t func) |
|
{ |
|
__call_rcu(head, func); |
|
} |
|
EXPORT_SYMBOL_GPL(call_rcu); |
|
|
|
|
|
/* Maximum number of jiffies to wait before draining a batch. */ |
|
#define KFREE_DRAIN_JIFFIES (HZ / 50) |
|
#define KFREE_N_BATCHES 2 |
|
#define FREE_N_CHANNELS 2 |
|
|
|
/** |
|
* struct kvfree_rcu_bulk_data - single block to store kvfree_rcu() pointers |
|
* @nr_records: Number of active pointers in the array |
|
* @next: Next bulk object in the block chain |
|
* @records: Array of the kvfree_rcu() pointers |
|
*/ |
|
struct kvfree_rcu_bulk_data { |
|
unsigned long nr_records; |
|
struct kvfree_rcu_bulk_data *next; |
|
void *records[]; |
|
}; |
|
|
|
/* |
|
* This macro defines how many entries the "records" array |
|
* will contain. It is based on the fact that the size of |
|
* kvfree_rcu_bulk_data structure becomes exactly one page. |
|
*/ |
|
#define KVFREE_BULK_MAX_ENTR \ |
|
((PAGE_SIZE - sizeof(struct kvfree_rcu_bulk_data)) / sizeof(void *)) |
|
|
|
/** |
|
* struct kfree_rcu_cpu_work - single batch of kfree_rcu() requests |
|
* @rcu_work: Let queue_rcu_work() invoke workqueue handler after grace period |
|
* @head_free: List of kfree_rcu() objects waiting for a grace period |
|
* @bkvhead_free: Bulk-List of kvfree_rcu() objects waiting for a grace period |
|
* @krcp: Pointer to @kfree_rcu_cpu structure |
|
*/ |
|
|
|
struct kfree_rcu_cpu_work { |
|
struct rcu_work rcu_work; |
|
struct rcu_head *head_free; |
|
struct kvfree_rcu_bulk_data *bkvhead_free[FREE_N_CHANNELS]; |
|
struct kfree_rcu_cpu *krcp; |
|
}; |
|
|
|
/** |
|
* struct kfree_rcu_cpu - batch up kfree_rcu() requests for RCU grace period |
|
* @head: List of kfree_rcu() objects not yet waiting for a grace period |
|
* @bkvhead: Bulk-List of kvfree_rcu() objects not yet waiting for a grace period |
|
* @krw_arr: Array of batches of kfree_rcu() objects waiting for a grace period |
|
* @lock: Synchronize access to this structure |
|
* @monitor_work: Promote @head to @head_free after KFREE_DRAIN_JIFFIES |
|
* @monitor_todo: Tracks whether a @monitor_work delayed work is pending |
|
* @initialized: The @rcu_work fields have been initialized |
|
* @count: Number of objects for which GP not started |
|
* @bkvcache: |
|
* A simple cache list that contains objects for reuse purpose. |
|
* In order to save some per-cpu space the list is singular. |
|
* Even though it is lockless an access has to be protected by the |
|
* per-cpu lock. |
|
* @page_cache_work: A work to refill the cache when it is empty |
|
* @work_in_progress: Indicates that page_cache_work is running |
|
* @hrtimer: A hrtimer for scheduling a page_cache_work |
|
* @nr_bkv_objs: number of allocated objects at @bkvcache. |
|
* |
|
* This is a per-CPU structure. The reason that it is not included in |
|
* the rcu_data structure is to permit this code to be extracted from |
|
* the RCU files. Such extraction could allow further optimization of |
|
* the interactions with the slab allocators. |
|
*/ |
|
struct kfree_rcu_cpu { |
|
struct rcu_head *head; |
|
struct kvfree_rcu_bulk_data *bkvhead[FREE_N_CHANNELS]; |
|
struct kfree_rcu_cpu_work krw_arr[KFREE_N_BATCHES]; |
|
raw_spinlock_t lock; |
|
struct delayed_work monitor_work; |
|
bool monitor_todo; |
|
bool initialized; |
|
int count; |
|
|
|
struct work_struct page_cache_work; |
|
atomic_t work_in_progress; |
|
struct hrtimer hrtimer; |
|
|
|
struct llist_head bkvcache; |
|
int nr_bkv_objs; |
|
}; |
|
|
|
static DEFINE_PER_CPU(struct kfree_rcu_cpu, krc) = { |
|
.lock = __RAW_SPIN_LOCK_UNLOCKED(krc.lock), |
|
}; |
|
|
|
static __always_inline void |
|
debug_rcu_bhead_unqueue(struct kvfree_rcu_bulk_data *bhead) |
|
{ |
|
#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD |
|
int i; |
|
|
|
for (i = 0; i < bhead->nr_records; i++) |
|
debug_rcu_head_unqueue((struct rcu_head *)(bhead->records[i])); |
|
#endif |
|
} |
|
|
|
static inline struct kfree_rcu_cpu * |
|
krc_this_cpu_lock(unsigned long *flags) |
|
{ |
|
struct kfree_rcu_cpu *krcp; |
|
|
|
local_irq_save(*flags); // For safely calling this_cpu_ptr(). |
|
krcp = this_cpu_ptr(&krc); |
|
raw_spin_lock(&krcp->lock); |
|
|
|
return krcp; |
|
} |
|
|
|
static inline void |
|
krc_this_cpu_unlock(struct kfree_rcu_cpu *krcp, unsigned long flags) |
|
{ |
|
raw_spin_unlock(&krcp->lock); |
|
local_irq_restore(flags); |
|
} |
|
|
|
static inline struct kvfree_rcu_bulk_data * |
|
get_cached_bnode(struct kfree_rcu_cpu *krcp) |
|
{ |
|
if (!krcp->nr_bkv_objs) |
|
return NULL; |
|
|
|
krcp->nr_bkv_objs--; |
|
return (struct kvfree_rcu_bulk_data *) |
|
llist_del_first(&krcp->bkvcache); |
|
} |
|
|
|
static inline bool |
|
put_cached_bnode(struct kfree_rcu_cpu *krcp, |
|
struct kvfree_rcu_bulk_data *bnode) |
|
{ |
|
// Check the limit. |
|
if (krcp->nr_bkv_objs >= rcu_min_cached_objs) |
|
return false; |
|
|
|
llist_add((struct llist_node *) bnode, &krcp->bkvcache); |
|
krcp->nr_bkv_objs++; |
|
return true; |
|
|
|
} |
|
|
|
/* |
|
* This function is invoked in workqueue context after a grace period. |
|
* It frees all the objects queued on ->bhead_free or ->head_free. |
|
*/ |
|
static void kfree_rcu_work(struct work_struct *work) |
|
{ |
|
unsigned long flags; |
|
struct kvfree_rcu_bulk_data *bkvhead[FREE_N_CHANNELS], *bnext; |
|
struct rcu_head *head, *next; |
|
struct kfree_rcu_cpu *krcp; |
|
struct kfree_rcu_cpu_work *krwp; |
|
int i, j; |
|
|
|
krwp = container_of(to_rcu_work(work), |
|
struct kfree_rcu_cpu_work, rcu_work); |
|
krcp = krwp->krcp; |
|
|
|
raw_spin_lock_irqsave(&krcp->lock, flags); |
|
// Channels 1 and 2. |
|
for (i = 0; i < FREE_N_CHANNELS; i++) { |
|
bkvhead[i] = krwp->bkvhead_free[i]; |
|
krwp->bkvhead_free[i] = NULL; |
|
} |
|
|
|
// Channel 3. |
|
head = krwp->head_free; |
|
krwp->head_free = NULL; |
|
raw_spin_unlock_irqrestore(&krcp->lock, flags); |
|
|
|
// Handle two first channels. |
|
for (i = 0; i < FREE_N_CHANNELS; i++) { |
|
for (; bkvhead[i]; bkvhead[i] = bnext) { |
|
bnext = bkvhead[i]->next; |
|
debug_rcu_bhead_unqueue(bkvhead[i]); |
|
|
|
rcu_lock_acquire(&rcu_callback_map); |
|
if (i == 0) { // kmalloc() / kfree(). |
|
trace_rcu_invoke_kfree_bulk_callback( |
|
rcu_state.name, bkvhead[i]->nr_records, |
|
bkvhead[i]->records); |
|
|
|
kfree_bulk(bkvhead[i]->nr_records, |
|
bkvhead[i]->records); |
|
} else { // vmalloc() / vfree(). |
|
for (j = 0; j < bkvhead[i]->nr_records; j++) { |
|
trace_rcu_invoke_kvfree_callback( |
|
rcu_state.name, |
|
bkvhead[i]->records[j], 0); |
|
|
|
vfree(bkvhead[i]->records[j]); |
|
} |
|
} |
|
rcu_lock_release(&rcu_callback_map); |
|
|
|
raw_spin_lock_irqsave(&krcp->lock, flags); |
|
if (put_cached_bnode(krcp, bkvhead[i])) |
|
bkvhead[i] = NULL; |
|
raw_spin_unlock_irqrestore(&krcp->lock, flags); |
|
|
|
if (bkvhead[i]) |
|
free_page((unsigned long) bkvhead[i]); |
|
|
|
cond_resched_tasks_rcu_qs(); |
|
} |
|
} |
|
|
|
/* |
|
* Emergency case only. It can happen under low memory |
|
* condition when an allocation gets failed, so the "bulk" |
|
* path can not be temporary maintained. |
|
*/ |
|
for (; head; head = next) { |
|
unsigned long offset = (unsigned long)head->func; |
|
void *ptr = (void *)head - offset; |
|
|
|
next = head->next; |
|
debug_rcu_head_unqueue((struct rcu_head *)ptr); |
|
rcu_lock_acquire(&rcu_callback_map); |
|
trace_rcu_invoke_kvfree_callback(rcu_state.name, head, offset); |
|
|
|
if (!WARN_ON_ONCE(!__is_kvfree_rcu_offset(offset))) |
|
kvfree(ptr); |
|
|
|
rcu_lock_release(&rcu_callback_map); |
|
cond_resched_tasks_rcu_qs(); |
|
} |
|
} |
|
|
|
/* |
|
* Schedule the kfree batch RCU work to run in workqueue context after a GP. |
|
* |
|
* This function is invoked by kfree_rcu_monitor() when the KFREE_DRAIN_JIFFIES |
|
* timeout has been reached. |
|
*/ |
|
static inline bool queue_kfree_rcu_work(struct kfree_rcu_cpu *krcp) |
|
{ |
|
struct kfree_rcu_cpu_work *krwp; |
|
bool repeat = false; |
|
int i, j; |
|
|
|
lockdep_assert_held(&krcp->lock); |
|
|
|
for (i = 0; i < KFREE_N_BATCHES; i++) { |
|
krwp = &(krcp->krw_arr[i]); |
|
|
|
/* |
|
* Try to detach bkvhead or head and attach it over any |
|
* available corresponding free channel. It can be that |
|
* a previous RCU batch is in progress, it means that |
|
* immediately to queue another one is not possible so |
|
* return false to tell caller to retry. |
|
*/ |
|
if ((krcp->bkvhead[0] && !krwp->bkvhead_free[0]) || |
|
(krcp->bkvhead[1] && !krwp->bkvhead_free[1]) || |
|
(krcp->head && !krwp->head_free)) { |
|
// Channel 1 corresponds to SLAB ptrs. |
|
// Channel 2 corresponds to vmalloc ptrs. |
|
for (j = 0; j < FREE_N_CHANNELS; j++) { |
|
if (!krwp->bkvhead_free[j]) { |
|
krwp->bkvhead_free[j] = krcp->bkvhead[j]; |
|
krcp->bkvhead[j] = NULL; |
|
} |
|
} |
|
|
|
// Channel 3 corresponds to emergency path. |
|
if (!krwp->head_free) { |
|
krwp->head_free = krcp->head; |
|
krcp->head = NULL; |
|
} |
|
|
|
WRITE_ONCE(krcp->count, 0); |
|
|
|
/* |
|
* One work is per one batch, so there are three |
|
* "free channels", the batch can handle. It can |
|
* be that the work is in the pending state when |
|
* channels have been detached following by each |
|
* other. |
|
*/ |
|
queue_rcu_work(system_wq, &krwp->rcu_work); |
|
} |
|
|
|
// Repeat if any "free" corresponding channel is still busy. |
|
if (krcp->bkvhead[0] || krcp->bkvhead[1] || krcp->head) |
|
repeat = true; |
|
} |
|
|
|
return !repeat; |
|
} |
|
|
|
static inline void kfree_rcu_drain_unlock(struct kfree_rcu_cpu *krcp, |
|
unsigned long flags) |
|
{ |
|
// Attempt to start a new batch. |
|
krcp->monitor_todo = false; |
|
if (queue_kfree_rcu_work(krcp)) { |
|
// Success! Our job is done here. |
|
raw_spin_unlock_irqrestore(&krcp->lock, flags); |
|
return; |
|
} |
|
|
|
// Previous RCU batch still in progress, try again later. |
|
krcp->monitor_todo = true; |
|
schedule_delayed_work(&krcp->monitor_work, KFREE_DRAIN_JIFFIES); |
|
raw_spin_unlock_irqrestore(&krcp->lock, flags); |
|
} |
|
|
|
/* |
|
* This function is invoked after the KFREE_DRAIN_JIFFIES timeout. |
|
* It invokes kfree_rcu_drain_unlock() to attempt to start another batch. |
|
*/ |
|
static void kfree_rcu_monitor(struct work_struct *work) |
|
{ |
|
unsigned long flags; |
|
struct kfree_rcu_cpu *krcp = container_of(work, struct kfree_rcu_cpu, |
|
monitor_work.work); |
|
|
|
raw_spin_lock_irqsave(&krcp->lock, flags); |
|
if (krcp->monitor_todo) |
|
kfree_rcu_drain_unlock(krcp, flags); |
|
else |
|
raw_spin_unlock_irqrestore(&krcp->lock, flags); |
|
} |
|
|
|
static enum hrtimer_restart |
|
schedule_page_work_fn(struct hrtimer *t) |
|
{ |
|
struct kfree_rcu_cpu *krcp = |
|
container_of(t, struct kfree_rcu_cpu, hrtimer); |
|
|
|
queue_work(system_highpri_wq, &krcp->page_cache_work); |
|
return HRTIMER_NORESTART; |
|
} |
|
|
|
static void fill_page_cache_func(struct work_struct *work) |
|
{ |
|
struct kvfree_rcu_bulk_data *bnode; |
|
struct kfree_rcu_cpu *krcp = |
|
container_of(work, struct kfree_rcu_cpu, |
|
page_cache_work); |
|
unsigned long flags; |
|
bool pushed; |
|
int i; |
|
|
|
for (i = 0; i < rcu_min_cached_objs; i++) { |
|
bnode = (struct kvfree_rcu_bulk_data *) |
|
__get_free_page(GFP_KERNEL | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN); |
|
|
|
if (bnode) { |
|
raw_spin_lock_irqsave(&krcp->lock, flags); |
|
pushed = put_cached_bnode(krcp, bnode); |
|
raw_spin_unlock_irqrestore(&krcp->lock, flags); |
|
|
|
if (!pushed) { |
|
free_page((unsigned long) bnode); |
|
break; |
|
} |
|
} |
|
} |
|
|
|
atomic_set(&krcp->work_in_progress, 0); |
|
} |
|
|
|
static void |
|
run_page_cache_worker(struct kfree_rcu_cpu *krcp) |
|
{ |
|
if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING && |
|
!atomic_xchg(&krcp->work_in_progress, 1)) { |
|
hrtimer_init(&krcp->hrtimer, CLOCK_MONOTONIC, |
|
HRTIMER_MODE_REL); |
|
krcp->hrtimer.function = schedule_page_work_fn; |
|
hrtimer_start(&krcp->hrtimer, 0, HRTIMER_MODE_REL); |
|
} |
|
} |
|
|
|
static inline bool |
|
kvfree_call_rcu_add_ptr_to_bulk(struct kfree_rcu_cpu *krcp, void *ptr) |
|
{ |
|
struct kvfree_rcu_bulk_data *bnode; |
|
int idx; |
|
|
|
if (unlikely(!krcp->initialized)) |
|
return false; |
|
|
|
lockdep_assert_held(&krcp->lock); |
|
idx = !!is_vmalloc_addr(ptr); |
|
|
|
/* Check if a new block is required. */ |
|
if (!krcp->bkvhead[idx] || |
|
krcp->bkvhead[idx]->nr_records == KVFREE_BULK_MAX_ENTR) { |
|
bnode = get_cached_bnode(krcp); |
|
/* Switch to emergency path. */ |
|
if (!bnode) |
|
return false; |
|
|
|
/* Initialize the new block. */ |
|
bnode->nr_records = 0; |
|
bnode->next = krcp->bkvhead[idx]; |
|
|
|
/* Attach it to the head. */ |
|
krcp->bkvhead[idx] = bnode; |
|
} |
|
|
|
/* Finally insert. */ |
|
krcp->bkvhead[idx]->records |
|
[krcp->bkvhead[idx]->nr_records++] = ptr; |
|
|
|
return true; |
|
} |
|
|
|
/* |
|
* Queue a request for lazy invocation of appropriate free routine after a |
|
* grace period. Please note there are three paths are maintained, two are the |
|
* main ones that use array of pointers interface and third one is emergency |
|
* one, that is used only when the main path can not be maintained temporary, |
|
* due to memory pressure. |
|
* |
|
* Each kvfree_call_rcu() request is added to a batch. The batch will be drained |
|
* every KFREE_DRAIN_JIFFIES number of jiffies. All the objects in the batch will |
|
* be free'd in workqueue context. This allows us to: batch requests together to |
|
* reduce the number of grace periods during heavy kfree_rcu()/kvfree_rcu() load. |
|
*/ |
|
void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func) |
|
{ |
|
unsigned long flags; |
|
struct kfree_rcu_cpu *krcp; |
|
bool success; |
|
void *ptr; |
|
|
|
if (head) { |
|
ptr = (void *) head - (unsigned long) func; |
|
} else { |
|
/* |
|
* Please note there is a limitation for the head-less |
|
* variant, that is why there is a clear rule for such |
|
* objects: it can be used from might_sleep() context |
|
* only. For other places please embed an rcu_head to |
|
* your data. |
|
*/ |
|
might_sleep(); |
|
ptr = (unsigned long *) func; |
|
} |
|
|
|
krcp = krc_this_cpu_lock(&flags); |
|
|
|
// Queue the object but don't yet schedule the batch. |
|
if (debug_rcu_head_queue(ptr)) { |
|
// Probable double kfree_rcu(), just leak. |
|
WARN_ONCE(1, "%s(): Double-freed call. rcu_head %p\n", |
|
__func__, head); |
|
|
|
// Mark as success and leave. |
|
success = true; |
|
goto unlock_return; |
|
} |
|
|
|
kasan_record_aux_stack(ptr); |
|
success = kvfree_call_rcu_add_ptr_to_bulk(krcp, ptr); |
|
if (!success) { |
|
run_page_cache_worker(krcp); |
|
|
|
if (head == NULL) |
|
// Inline if kvfree_rcu(one_arg) call. |
|
goto unlock_return; |
|
|
|
head->func = func; |
|
head->next = krcp->head; |
|
krcp->head = head; |
|
success = true; |
|
} |
|
|
|
WRITE_ONCE(krcp->count, krcp->count + 1); |
|
|
|
// Set timer to drain after KFREE_DRAIN_JIFFIES. |
|
if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING && |
|
!krcp->monitor_todo) { |
|
krcp->monitor_todo = true; |
|
schedule_delayed_work(&krcp->monitor_work, KFREE_DRAIN_JIFFIES); |
|
} |
|
|
|
unlock_return: |
|
krc_this_cpu_unlock(krcp, flags); |
|
|
|
/* |
|
* Inline kvfree() after synchronize_rcu(). We can do |
|
* it from might_sleep() context only, so the current |
|
* CPU can pass the QS state. |
|
*/ |
|
if (!success) { |
|
debug_rcu_head_unqueue((struct rcu_head *) ptr); |
|
synchronize_rcu(); |
|
kvfree(ptr); |
|
} |
|
} |
|
EXPORT_SYMBOL_GPL(kvfree_call_rcu); |
|
|
|
static unsigned long |
|
kfree_rcu_shrink_count(struct shrinker *shrink, struct shrink_control *sc) |
|
{ |
|
int cpu; |
|
unsigned long count = 0; |
|
|
|
/* Snapshot count of all CPUs */ |
|
for_each_possible_cpu(cpu) { |
|
struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu); |
|
|
|
count += READ_ONCE(krcp->count); |
|
} |
|
|
|
return count; |
|
} |
|
|
|
static unsigned long |
|
kfree_rcu_shrink_scan(struct shrinker *shrink, struct shrink_control *sc) |
|
{ |
|
int cpu, freed = 0; |
|
unsigned long flags; |
|
|
|
for_each_possible_cpu(cpu) { |
|
int count; |
|
struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu); |
|
|
|
count = krcp->count; |
|
raw_spin_lock_irqsave(&krcp->lock, flags); |
|
if (krcp->monitor_todo) |
|
kfree_rcu_drain_unlock(krcp, flags); |
|
else |
|
raw_spin_unlock_irqrestore(&krcp->lock, flags); |
|
|
|
sc->nr_to_scan -= count; |
|
freed += count; |
|
|
|
if (sc->nr_to_scan <= 0) |
|
break; |
|
} |
|
|
|
return freed == 0 ? SHRINK_STOP : freed; |
|
} |
|
|
|
static struct shrinker kfree_rcu_shrinker = { |
|
.count_objects = kfree_rcu_shrink_count, |
|
.scan_objects = kfree_rcu_shrink_scan, |
|
.batch = 0, |
|
.seeks = DEFAULT_SEEKS, |
|
}; |
|
|
|
void __init kfree_rcu_scheduler_running(void) |
|
{ |
|
int cpu; |
|
unsigned long flags; |
|
|
|
for_each_possible_cpu(cpu) { |
|
struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu); |
|
|
|
raw_spin_lock_irqsave(&krcp->lock, flags); |
|
if (!krcp->head || krcp->monitor_todo) { |
|
raw_spin_unlock_irqrestore(&krcp->lock, flags); |
|
continue; |
|
} |
|
krcp->monitor_todo = true; |
|
schedule_delayed_work_on(cpu, &krcp->monitor_work, |
|
KFREE_DRAIN_JIFFIES); |
|
raw_spin_unlock_irqrestore(&krcp->lock, flags); |
|
} |
|
} |
|
|
|
/* |
|
* During early boot, any blocking grace-period wait automatically |
|
* implies a grace period. Later on, this is never the case for PREEMPTION. |
|
* |
|
* However, because a context switch is a grace period for !PREEMPTION, any |
|
* blocking grace-period wait automatically implies a grace period if |
|
* there is only one CPU online at any point time during execution of |
|
* either synchronize_rcu() or synchronize_rcu_expedited(). It is OK to |
|
* occasionally incorrectly indicate that there are multiple CPUs online |
|
* when there was in fact only one the whole time, as this just adds some |
|
* overhead: RCU still operates correctly. |
|
*/ |
|
static int rcu_blocking_is_gp(void) |
|
{ |
|
int ret; |
|
|
|
if (IS_ENABLED(CONFIG_PREEMPTION)) |
|
return rcu_scheduler_active == RCU_SCHEDULER_INACTIVE; |
|
might_sleep(); /* Check for RCU read-side critical section. */ |
|
preempt_disable(); |
|
/* |
|
* If the rcu_state.n_online_cpus counter is equal to one, |
|
* there is only one CPU, and that CPU sees all prior accesses |
|
* made by any CPU that was online at the time of its access. |
|
* Furthermore, if this counter is equal to one, its value cannot |
|
* change until after the preempt_enable() below. |
|
* |
|
* Furthermore, if rcu_state.n_online_cpus is equal to one here, |
|
* all later CPUs (both this one and any that come online later |
|
* on) are guaranteed to see all accesses prior to this point |
|
* in the code, without the need for additional memory barriers. |
|
* Those memory barriers are provided by CPU-hotplug code. |
|
*/ |
|
ret = READ_ONCE(rcu_state.n_online_cpus) <= 1; |
|
preempt_enable(); |
|
return ret; |
|
} |
|
|
|
/** |
|
* synchronize_rcu - wait until a grace period has elapsed. |
|
* |
|
* Control will return to the caller some time after a full grace |
|
* period has elapsed, in other words after all currently executing RCU |
|
* read-side critical sections have completed. Note, however, that |
|
* upon return from synchronize_rcu(), the caller might well be executing |
|
* concurrently with new RCU read-side critical sections that began while |
|
* synchronize_rcu() was waiting. RCU read-side critical sections are |
|
* delimited by rcu_read_lock() and rcu_read_unlock(), and may be nested. |
|
* In addition, regions of code across which interrupts, preemption, or |
|
* softirqs have been disabled also serve as RCU read-side critical |
|
* sections. This includes hardware interrupt handlers, softirq handlers, |
|
* and NMI handlers. |
|
* |
|
* Note that this guarantee implies further memory-ordering guarantees. |
|
* On systems with more than one CPU, when synchronize_rcu() returns, |
|
* each CPU is guaranteed to have executed a full memory barrier since |
|
* the end of its last RCU read-side critical section whose beginning |
|
* preceded the call to synchronize_rcu(). In addition, each CPU having |
|
* an RCU read-side critical section that extends beyond the return from |
|
* synchronize_rcu() is guaranteed to have executed a full memory barrier |
|
* after the beginning of synchronize_rcu() and before the beginning of |
|
* that RCU read-side critical section. Note that these guarantees include |
|
* CPUs that are offline, idle, or executing in user mode, as well as CPUs |
|
* that are executing in the kernel. |
|
* |
|
* Furthermore, if CPU A invoked synchronize_rcu(), which returned |
|
* to its caller on CPU B, then both CPU A and CPU B are guaranteed |
|
* to have executed a full memory barrier during the execution of |
|
* synchronize_rcu() -- even if CPU A and CPU B are the same CPU (but |
|
* again only if the system has more than one CPU). |
|
*/ |
|
void synchronize_rcu(void) |
|
{ |
|
RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) || |
|
lock_is_held(&rcu_lock_map) || |
|
lock_is_held(&rcu_sched_lock_map), |
|
"Illegal synchronize_rcu() in RCU read-side critical section"); |
|
if (rcu_blocking_is_gp()) |
|
return; // Context allows vacuous grace periods. |
|
if (rcu_gp_is_expedited()) |
|
synchronize_rcu_expedited(); |
|
else |
|
wait_rcu_gp(call_rcu); |
|
} |
|
EXPORT_SYMBOL_GPL(synchronize_rcu); |
|
|
|
/** |
|
* get_state_synchronize_rcu - Snapshot current RCU state |
|
* |
|
* Returns a cookie that is used by a later call to cond_synchronize_rcu() |
|
* to determine whether or not a full grace period has elapsed in the |
|
* meantime. |
|
*/ |
|
unsigned long get_state_synchronize_rcu(void) |
|
{ |
|
/* |
|
* Any prior manipulation of RCU-protected data must happen |
|
* before the load from ->gp_seq. |
|
*/ |
|
smp_mb(); /* ^^^ */ |
|
return rcu_seq_snap(&rcu_state.gp_seq); |
|
} |
|
EXPORT_SYMBOL_GPL(get_state_synchronize_rcu); |
|
|
|
/** |
|
* cond_synchronize_rcu - Conditionally wait for an RCU grace period |
|
* |
|
* @oldstate: return value from earlier call to get_state_synchronize_rcu() |
|
* |
|
* If a full RCU grace period has elapsed since the earlier call to |
|
* get_state_synchronize_rcu(), just return. Otherwise, invoke |
|
* synchronize_rcu() to wait for a full grace period. |
|
* |
|
* Yes, this function does not take counter wrap into account. But |
|
* counter wrap is harmless. If the counter wraps, we have waited for |
|
* more than 2 billion grace periods (and way more on a 64-bit system!), |
|
* so waiting for one additional grace period should be just fine. |
|
*/ |
|
void cond_synchronize_rcu(unsigned long oldstate) |
|
{ |
|
if (!rcu_seq_done(&rcu_state.gp_seq, oldstate)) |
|
synchronize_rcu(); |
|
else |
|
smp_mb(); /* Ensure GP ends before subsequent accesses. */ |
|
} |
|
EXPORT_SYMBOL_GPL(cond_synchronize_rcu); |
|
|
|
/* |
|
* Check to see if there is any immediate RCU-related work to be done by |
|
* the current CPU, returning 1 if so and zero otherwise. The checks are |
|
* in order of increasing expense: checks that can be carried out against |
|
* CPU-local state are performed first. However, we must check for CPU |
|
* stalls first, else we might not get a chance. |
|
*/ |
|
static int rcu_pending(int user) |
|
{ |
|
bool gp_in_progress; |
|
struct rcu_data *rdp = this_cpu_ptr(&rcu_data); |
|
struct rcu_node *rnp = rdp->mynode; |
|
|
|
lockdep_assert_irqs_disabled(); |
|
|
|
/* Check for CPU stalls, if enabled. */ |
|
check_cpu_stall(rdp); |
|
|
|
/* Does this CPU need a deferred NOCB wakeup? */ |
|
if (rcu_nocb_need_deferred_wakeup(rdp)) |
|
return 1; |
|
|
|
/* Is this a nohz_full CPU in userspace or idle? (Ignore RCU if so.) */ |
|
if ((user || rcu_is_cpu_rrupt_from_idle()) && rcu_nohz_full_cpu()) |
|
return 0; |
|
|
|
/* Is the RCU core waiting for a quiescent state from this CPU? */ |
|
gp_in_progress = rcu_gp_in_progress(); |
|
if (rdp->core_needs_qs && !rdp->cpu_no_qs.b.norm && gp_in_progress) |
|
return 1; |
|
|
|
/* Does this CPU have callbacks ready to invoke? */ |
|
if (!rcu_segcblist_is_offloaded(&rdp->cblist) && |
|
rcu_segcblist_ready_cbs(&rdp->cblist)) |
|
return 1; |
|
|
|
/* Has RCU gone idle with this CPU needing another grace period? */ |
|
if (!gp_in_progress && rcu_segcblist_is_enabled(&rdp->cblist) && |
|
!rcu_segcblist_is_offloaded(&rdp->cblist) && |
|
!rcu_segcblist_restempty(&rdp->cblist, RCU_NEXT_READY_TAIL)) |
|
return 1; |
|
|
|
/* Have RCU grace period completed or started? */ |
|
if (rcu_seq_current(&rnp->gp_seq) != rdp->gp_seq || |
|
unlikely(READ_ONCE(rdp->gpwrap))) /* outside lock */ |
|
return 1; |
|
|
|
/* nothing to do */ |
|
return 0; |
|
} |
|
|
|
/* |
|
* Helper function for rcu_barrier() tracing. If tracing is disabled, |
|
* the compiler is expected to optimize this away. |
|
*/ |
|
static void rcu_barrier_trace(const char *s, int cpu, unsigned long done) |
|
{ |
|
trace_rcu_barrier(rcu_state.name, s, cpu, |
|
atomic_read(&rcu_state.barrier_cpu_count), done); |
|
} |
|
|
|
/* |
|
* RCU callback function for rcu_barrier(). If we are last, wake |
|
* up the task executing rcu_barrier(). |
|
* |
|
* Note that the value of rcu_state.barrier_sequence must be captured |
|
* before the atomic_dec_and_test(). Otherwise, if this CPU is not last, |
|
* other CPUs might count the value down to zero before this CPU gets |
|
* around to invoking rcu_barrier_trace(), which might result in bogus |
|
* data from the next instance of rcu_barrier(). |
|
*/ |
|
static void rcu_barrier_callback(struct rcu_head *rhp) |
|
{ |
|
unsigned long __maybe_unused s = rcu_state.barrier_sequence; |
|
|
|
if (atomic_dec_and_test(&rcu_state.barrier_cpu_count)) { |
|
rcu_barrier_trace(TPS("LastCB"), -1, s); |
|
complete(&rcu_state.barrier_completion); |
|
} else { |
|
rcu_barrier_trace(TPS("CB"), -1, s); |
|
} |
|
} |
|
|
|
/* |
|
* Called with preemption disabled, and from cross-cpu IRQ context. |
|
*/ |
|
static void rcu_barrier_func(void *cpu_in) |
|
{ |
|
uintptr_t cpu = (uintptr_t)cpu_in; |
|
struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); |
|
|
|
rcu_barrier_trace(TPS("IRQ"), -1, rcu_state.barrier_sequence); |
|
rdp->barrier_head.func = rcu_barrier_callback; |
|
debug_rcu_head_queue(&rdp->barrier_head); |
|
rcu_nocb_lock(rdp); |
|
WARN_ON_ONCE(!rcu_nocb_flush_bypass(rdp, NULL, jiffies)); |
|
if (rcu_segcblist_entrain(&rdp->cblist, &rdp->barrier_head)) { |
|
atomic_inc(&rcu_state.barrier_cpu_count); |
|
} else { |
|
debug_rcu_head_unqueue(&rdp->barrier_head); |
|
rcu_barrier_trace(TPS("IRQNQ"), -1, |
|
rcu_state.barrier_sequence); |
|
} |
|
rcu_nocb_unlock(rdp); |
|
} |
|
|
|
/** |
|
* rcu_barrier - Wait until all in-flight call_rcu() callbacks complete. |
|
* |
|
* Note that this primitive does not necessarily wait for an RCU grace period |
|
* to complete. For example, if there are no RCU callbacks queued anywhere |
|
* in the system, then rcu_barrier() is within its rights to return |
|
* immediately, without waiting for anything, much less an RCU grace period. |
|
*/ |
|
void rcu_barrier(void) |
|
{ |
|
uintptr_t cpu; |
|
struct rcu_data *rdp; |
|
unsigned long s = rcu_seq_snap(&rcu_state.barrier_sequence); |
|
|
|
rcu_barrier_trace(TPS("Begin"), -1, s); |
|
|
|
/* Take mutex to serialize concurrent rcu_barrier() requests. */ |
|
mutex_lock(&rcu_state.barrier_mutex); |
|
|
|
/* Did someone else do our work for us? */ |
|
if (rcu_seq_done(&rcu_state.barrier_sequence, s)) { |
|
rcu_barrier_trace(TPS("EarlyExit"), -1, |
|
rcu_state.barrier_sequence); |
|
smp_mb(); /* caller's subsequent code after above check. */ |
|
mutex_unlock(&rcu_state.barrier_mutex); |
|
return; |
|
} |
|
|
|
/* Mark the start of the barrier operation. */ |
|
rcu_seq_start(&rcu_state.barrier_sequence); |
|
rcu_barrier_trace(TPS("Inc1"), -1, rcu_state.barrier_sequence); |
|
|
|
/* |
|
* Initialize the count to two rather than to zero in order |
|
* to avoid a too-soon return to zero in case of an immediate |
|
* invocation of the just-enqueued callback (or preemption of |
|
* this task). Exclude CPU-hotplug operations to ensure that no |
|
* offline non-offloaded CPU has callbacks queued. |
|
*/ |
|
init_completion(&rcu_state.barrier_completion); |
|
atomic_set(&rcu_state.barrier_cpu_count, 2); |
|
get_online_cpus(); |
|
|
|
/* |
|
* Force each CPU with callbacks to register a new callback. |
|
* When that callback is invoked, we will know that all of the |
|
* corresponding CPU's preceding callbacks have been invoked. |
|
*/ |
|
for_each_possible_cpu(cpu) { |
|
rdp = per_cpu_ptr(&rcu_data, cpu); |
|
if (cpu_is_offline(cpu) && |
|
!rcu_segcblist_is_offloaded(&rdp->cblist)) |
|
continue; |
|
if (rcu_segcblist_n_cbs(&rdp->cblist) && cpu_online(cpu)) { |
|
rcu_barrier_trace(TPS("OnlineQ"), cpu, |
|
rcu_state.barrier_sequence); |
|
smp_call_function_single(cpu, rcu_barrier_func, (void *)cpu, 1); |
|
} else if (rcu_segcblist_n_cbs(&rdp->cblist) && |
|
cpu_is_offline(cpu)) { |
|
rcu_barrier_trace(TPS("OfflineNoCBQ"), cpu, |
|
rcu_state.barrier_sequence); |
|
local_irq_disable(); |
|
rcu_barrier_func((void *)cpu); |
|
local_irq_enable(); |
|
} else if (cpu_is_offline(cpu)) { |
|
rcu_barrier_trace(TPS("OfflineNoCBNoQ"), cpu, |
|
rcu_state.barrier_sequence); |
|
} else { |
|
rcu_barrier_trace(TPS("OnlineNQ"), cpu, |
|
rcu_state.barrier_sequence); |
|
} |
|
} |
|
put_online_cpus(); |
|
|
|
/* |
|
* Now that we have an rcu_barrier_callback() callback on each |
|
* CPU, and thus each counted, remove the initial count. |
|
*/ |
|
if (atomic_sub_and_test(2, &rcu_state.barrier_cpu_count)) |
|
complete(&rcu_state.barrier_completion); |
|
|
|
/* Wait for all rcu_barrier_callback() callbacks to be invoked. */ |
|
wait_for_completion(&rcu_state.barrier_completion); |
|
|
|
/* Mark the end of the barrier operation. */ |
|
rcu_barrier_trace(TPS("Inc2"), -1, rcu_state.barrier_sequence); |
|
rcu_seq_end(&rcu_state.barrier_sequence); |
|
|
|
/* Other rcu_barrier() invocations can now safely proceed. */ |
|
mutex_unlock(&rcu_state.barrier_mutex); |
|
} |
|
EXPORT_SYMBOL_GPL(rcu_barrier); |
|
|
|
/* |
|
* Propagate ->qsinitmask bits up the rcu_node tree to account for the |
|
* first CPU in a given leaf rcu_node structure coming online. The caller |
|
* must hold the corresponding leaf rcu_node ->lock with interrrupts |
|
* disabled. |
|
*/ |
|
static void rcu_init_new_rnp(struct rcu_node *rnp_leaf) |
|
{ |
|
long mask; |
|
long oldmask; |
|
struct rcu_node *rnp = rnp_leaf; |
|
|
|
raw_lockdep_assert_held_rcu_node(rnp_leaf); |
|
WARN_ON_ONCE(rnp->wait_blkd_tasks); |
|
for (;;) { |
|
mask = rnp->grpmask; |
|
rnp = rnp->parent; |
|
if (rnp == NULL) |
|
return; |
|
raw_spin_lock_rcu_node(rnp); /* Interrupts already disabled. */ |
|
oldmask = rnp->qsmaskinit; |
|
rnp->qsmaskinit |= mask; |
|
raw_spin_unlock_rcu_node(rnp); /* Interrupts remain disabled. */ |
|
if (oldmask) |
|
return; |
|
} |
|
} |
|
|
|
/* |
|
* Do boot-time initialization of a CPU's per-CPU RCU data. |
|
*/ |
|
static void __init |
|
rcu_boot_init_percpu_data(int cpu) |
|
{ |
|
struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); |
|
|
|
/* Set up local state, ensuring consistent view of global state. */ |
|
rdp->grpmask = leaf_node_cpu_bit(rdp->mynode, cpu); |
|
INIT_WORK(&rdp->strict_work, strict_work_handler); |
|
WARN_ON_ONCE(rdp->dynticks_nesting != 1); |
|
WARN_ON_ONCE(rcu_dynticks_in_eqs(rcu_dynticks_snap(rdp))); |
|
rdp->rcu_ofl_gp_seq = rcu_state.gp_seq; |
|
rdp->rcu_ofl_gp_flags = RCU_GP_CLEANED; |
|
rdp->rcu_onl_gp_seq = rcu_state.gp_seq; |
|
rdp->rcu_onl_gp_flags = RCU_GP_CLEANED; |
|
rdp->cpu = cpu; |
|
rcu_boot_init_nocb_percpu_data(rdp); |
|
} |
|
|
|
/* |
|
* Invoked early in the CPU-online process, when pretty much all services |
|
* are available. The incoming CPU is not present. |
|
* |
|
* Initializes a CPU's per-CPU RCU data. Note that only one online or |
|
* offline event can be happening at a given time. Note also that we can |
|
* accept some slop in the rsp->gp_seq access due to the fact that this |
|
* CPU cannot possibly have any non-offloaded RCU callbacks in flight yet. |
|
* And any offloaded callbacks are being numbered elsewhere. |
|
*/ |
|
int rcutree_prepare_cpu(unsigned int cpu) |
|
{ |
|
unsigned long flags; |
|
struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); |
|
struct rcu_node *rnp = rcu_get_root(); |
|
|
|
/* Set up local state, ensuring consistent view of global state. */ |
|
raw_spin_lock_irqsave_rcu_node(rnp, flags); |
|
rdp->qlen_last_fqs_check = 0; |
|
rdp->n_force_qs_snap = rcu_state.n_force_qs; |
|
rdp->blimit = blimit; |
|
rdp->dynticks_nesting = 1; /* CPU not up, no tearing. */ |
|
rcu_dynticks_eqs_online(); |
|
raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */ |
|
/* |
|
* Lock in case the CB/GP kthreads are still around handling |
|
* old callbacks (longer term we should flush all callbacks |
|
* before completing CPU offline) |
|
*/ |
|
rcu_nocb_lock(rdp); |
|
if (rcu_segcblist_empty(&rdp->cblist)) /* No early-boot CBs? */ |
|
rcu_segcblist_init(&rdp->cblist); /* Re-enable callbacks. */ |
|
rcu_nocb_unlock(rdp); |
|
|
|
/* |
|
* Add CPU to leaf rcu_node pending-online bitmask. Any needed |
|
* propagation up the rcu_node tree will happen at the beginning |
|
* of the next grace period. |
|
*/ |
|
rnp = rdp->mynode; |
|
raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */ |
|
rdp->beenonline = true; /* We have now been online. */ |
|
rdp->gp_seq = READ_ONCE(rnp->gp_seq); |
|
rdp->gp_seq_needed = rdp->gp_seq; |
|
rdp->cpu_no_qs.b.norm = true; |
|
rdp->core_needs_qs = false; |
|
rdp->rcu_iw_pending = false; |
|
rdp->rcu_iw = IRQ_WORK_INIT_HARD(rcu_iw_handler); |
|
rdp->rcu_iw_gp_seq = rdp->gp_seq - 1; |
|
trace_rcu_grace_period(rcu_state.name, rdp->gp_seq, TPS("cpuonl")); |
|
raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
|
rcu_prepare_kthreads(cpu); |
|
rcu_spawn_cpu_nocb_kthread(cpu); |
|
WRITE_ONCE(rcu_state.n_online_cpus, rcu_state.n_online_cpus + 1); |
|
|
|
return 0; |
|
} |
|
|
|
/* |
|
* Update RCU priority boot kthread affinity for CPU-hotplug changes. |
|
*/ |
|
static void rcutree_affinity_setting(unsigned int cpu, int outgoing) |
|
{ |
|
struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); |
|
|
|
rcu_boost_kthread_setaffinity(rdp->mynode, outgoing); |
|
} |
|
|
|
/* |
|
* Near the end of the CPU-online process. Pretty much all services |
|
* enabled, and the CPU is now very much alive. |
|
*/ |
|
int rcutree_online_cpu(unsigned int cpu) |
|
{ |
|
unsigned long flags; |
|
struct rcu_data *rdp; |
|
struct rcu_node *rnp; |
|
|
|
rdp = per_cpu_ptr(&rcu_data, cpu); |
|
rnp = rdp->mynode; |
|
raw_spin_lock_irqsave_rcu_node(rnp, flags); |
|
rnp->ffmask |= rdp->grpmask; |
|
raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
|
if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE) |
|
return 0; /* Too early in boot for scheduler work. */ |
|
sync_sched_exp_online_cleanup(cpu); |
|
rcutree_affinity_setting(cpu, -1); |
|
|
|
// Stop-machine done, so allow nohz_full to disable tick. |
|
tick_dep_clear(TICK_DEP_BIT_RCU); |
|
return 0; |
|
} |
|
|
|
/* |
|
* Near the beginning of the process. The CPU is still very much alive |
|
* with pretty much all services enabled. |
|
*/ |
|
int rcutree_offline_cpu(unsigned int cpu) |
|
{ |
|
unsigned long flags; |
|
struct rcu_data *rdp; |
|
struct rcu_node *rnp; |
|
|
|
rdp = per_cpu_ptr(&rcu_data, cpu); |
|
rnp = rdp->mynode; |
|
raw_spin_lock_irqsave_rcu_node(rnp, flags); |
|
rnp->ffmask &= ~rdp->grpmask; |
|
raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
|
|
|
rcutree_affinity_setting(cpu, cpu); |
|
|
|
// nohz_full CPUs need the tick for stop-machine to work quickly |
|
tick_dep_set(TICK_DEP_BIT_RCU); |
|
return 0; |
|
} |
|
|
|
/* |
|
* Mark the specified CPU as being online so that subsequent grace periods |
|
* (both expedited and normal) will wait on it. Note that this means that |
|
* incoming CPUs are not allowed to use RCU read-side critical sections |
|
* until this function is called. Failing to observe this restriction |
|
* will result in lockdep splats. |
|
* |
|
* Note that this function is special in that it is invoked directly |
|
* from the incoming CPU rather than from the cpuhp_step mechanism. |
|
* This is because this function must be invoked at a precise location. |
|
*/ |
|
void rcu_cpu_starting(unsigned int cpu) |
|
{ |
|
unsigned long flags; |
|
unsigned long mask; |
|
struct rcu_data *rdp; |
|
struct rcu_node *rnp; |
|
bool newcpu; |
|
|
|
rdp = per_cpu_ptr(&rcu_data, cpu); |
|
if (rdp->cpu_started) |
|
return; |
|
rdp->cpu_started = true; |
|
|
|
rnp = rdp->mynode; |
|
mask = rdp->grpmask; |
|
WRITE_ONCE(rnp->ofl_seq, rnp->ofl_seq + 1); |
|
WARN_ON_ONCE(!(rnp->ofl_seq & 0x1)); |
|
smp_mb(); // Pair with rcu_gp_cleanup()'s ->ofl_seq barrier(). |
|
raw_spin_lock_irqsave_rcu_node(rnp, flags); |
|
WRITE_ONCE(rnp->qsmaskinitnext, rnp->qsmaskinitnext | mask); |
|
newcpu = !(rnp->expmaskinitnext & mask); |
|
rnp->expmaskinitnext |= mask; |
|
/* Allow lockless access for expedited grace periods. */ |
|
smp_store_release(&rcu_state.ncpus, rcu_state.ncpus + newcpu); /* ^^^ */ |
|
ASSERT_EXCLUSIVE_WRITER(rcu_state.ncpus); |
|
rcu_gpnum_ovf(rnp, rdp); /* Offline-induced counter wrap? */ |
|
rdp->rcu_onl_gp_seq = READ_ONCE(rcu_state.gp_seq); |
|
rdp->rcu_onl_gp_flags = READ_ONCE(rcu_state.gp_flags); |
|
|
|
/* An incoming CPU should never be blocking a grace period. */ |
|
if (WARN_ON_ONCE(rnp->qsmask & mask)) { /* RCU waiting on incoming CPU? */ |
|
rcu_disable_urgency_upon_qs(rdp); |
|
/* Report QS -after- changing ->qsmaskinitnext! */ |
|
rcu_report_qs_rnp(mask, rnp, rnp->gp_seq, flags); |
|
} else { |
|
raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
|
} |
|
smp_mb(); // Pair with rcu_gp_cleanup()'s ->ofl_seq barrier(). |
|
WRITE_ONCE(rnp->ofl_seq, rnp->ofl_seq + 1); |
|
WARN_ON_ONCE(rnp->ofl_seq & 0x1); |
|
smp_mb(); /* Ensure RCU read-side usage follows above initialization. */ |
|
} |
|
|
|
/* |
|
* The outgoing function has no further need of RCU, so remove it from |
|
* the rcu_node tree's ->qsmaskinitnext bit masks. |
|
* |
|
* Note that this function is special in that it is invoked directly |
|
* from the outgoing CPU rather than from the cpuhp_step mechanism. |
|
* This is because this function must be invoked at a precise location. |
|
*/ |
|
void rcu_report_dead(unsigned int cpu) |
|
{ |
|
unsigned long flags; |
|
unsigned long mask; |
|
struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); |
|
struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */ |
|
|
|
// Do any dangling deferred wakeups. |
|
do_nocb_deferred_wakeup(rdp); |
|
|
|
/* QS for any half-done expedited grace period. */ |
|
preempt_disable(); |
|
rcu_report_exp_rdp(this_cpu_ptr(&rcu_data)); |
|
preempt_enable(); |
|
rcu_preempt_deferred_qs(current); |
|
|
|
/* Remove outgoing CPU from mask in the leaf rcu_node structure. */ |
|
mask = rdp->grpmask; |
|
WRITE_ONCE(rnp->ofl_seq, rnp->ofl_seq + 1); |
|
WARN_ON_ONCE(!(rnp->ofl_seq & 0x1)); |
|
smp_mb(); // Pair with rcu_gp_cleanup()'s ->ofl_seq barrier(). |
|
raw_spin_lock(&rcu_state.ofl_lock); |
|
raw_spin_lock_irqsave_rcu_node(rnp, flags); /* Enforce GP memory-order guarantee. */ |
|
rdp->rcu_ofl_gp_seq = READ_ONCE(rcu_state.gp_seq); |
|
rdp->rcu_ofl_gp_flags = READ_ONCE(rcu_state.gp_flags); |
|
if (rnp->qsmask & mask) { /* RCU waiting on outgoing CPU? */ |
|
/* Report quiescent state -before- changing ->qsmaskinitnext! */ |
|
rcu_report_qs_rnp(mask, rnp, rnp->gp_seq, flags); |
|
raw_spin_lock_irqsave_rcu_node(rnp, flags); |
|
} |
|
WRITE_ONCE(rnp->qsmaskinitnext, rnp->qsmaskinitnext & ~mask); |
|
raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
|
raw_spin_unlock(&rcu_state.ofl_lock); |
|
smp_mb(); // Pair with rcu_gp_cleanup()'s ->ofl_seq barrier(). |
|
WRITE_ONCE(rnp->ofl_seq, rnp->ofl_seq + 1); |
|
WARN_ON_ONCE(rnp->ofl_seq & 0x1); |
|
|
|
rdp->cpu_started = false; |
|
} |
|
|
|
#ifdef CONFIG_HOTPLUG_CPU |
|
/* |
|
* The outgoing CPU has just passed through the dying-idle state, and we |
|
* are being invoked from the CPU that was IPIed to continue the offline |
|
* operation. Migrate the outgoing CPU's callbacks to the current CPU. |
|
*/ |
|
void rcutree_migrate_callbacks(int cpu) |
|
{ |
|
unsigned long flags; |
|
struct rcu_data *my_rdp; |
|
struct rcu_node *my_rnp; |
|
struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); |
|
bool needwake; |
|
|
|
if (rcu_segcblist_is_offloaded(&rdp->cblist) || |
|
rcu_segcblist_empty(&rdp->cblist)) |
|
return; /* No callbacks to migrate. */ |
|
|
|
local_irq_save(flags); |
|
my_rdp = this_cpu_ptr(&rcu_data); |
|
my_rnp = my_rdp->mynode; |
|
rcu_nocb_lock(my_rdp); /* irqs already disabled. */ |
|
WARN_ON_ONCE(!rcu_nocb_flush_bypass(my_rdp, NULL, jiffies)); |
|
raw_spin_lock_rcu_node(my_rnp); /* irqs already disabled. */ |
|
/* Leverage recent GPs and set GP for new callbacks. */ |
|
needwake = rcu_advance_cbs(my_rnp, rdp) || |
|
rcu_advance_cbs(my_rnp, my_rdp); |
|
rcu_segcblist_merge(&my_rdp->cblist, &rdp->cblist); |
|
needwake = needwake || rcu_advance_cbs(my_rnp, my_rdp); |
|
rcu_segcblist_disable(&rdp->cblist); |
|
WARN_ON_ONCE(rcu_segcblist_empty(&my_rdp->cblist) != |
|
!rcu_segcblist_n_cbs(&my_rdp->cblist)); |
|
if (rcu_segcblist_is_offloaded(&my_rdp->cblist)) { |
|
raw_spin_unlock_rcu_node(my_rnp); /* irqs remain disabled. */ |
|
__call_rcu_nocb_wake(my_rdp, true, flags); |
|
} else { |
|
rcu_nocb_unlock(my_rdp); /* irqs remain disabled. */ |
|
raw_spin_unlock_irqrestore_rcu_node(my_rnp, flags); |
|
} |
|
if (needwake) |
|
rcu_gp_kthread_wake(); |
|
lockdep_assert_irqs_enabled(); |
|
WARN_ONCE(rcu_segcblist_n_cbs(&rdp->cblist) != 0 || |
|
!rcu_segcblist_empty(&rdp->cblist), |
|
"rcu_cleanup_dead_cpu: Callbacks on offline CPU %d: qlen=%lu, 1stCB=%p\n", |
|
cpu, rcu_segcblist_n_cbs(&rdp->cblist), |
|
rcu_segcblist_first_cb(&rdp->cblist)); |
|
} |
|
#endif |
|
|
|
/* |
|
* On non-huge systems, use expedited RCU grace periods to make suspend |
|
* and hibernation run faster. |
|
*/ |
|
static int rcu_pm_notify(struct notifier_block *self, |
|
unsigned long action, void *hcpu) |
|
{ |
|
switch (action) { |
|
case PM_HIBERNATION_PREPARE: |
|
case PM_SUSPEND_PREPARE: |
|
rcu_expedite_gp(); |
|
break; |
|
case PM_POST_HIBERNATION: |
|
case PM_POST_SUSPEND: |
|
rcu_unexpedite_gp(); |
|
break; |
|
default: |
|
break; |
|
} |
|
return NOTIFY_OK; |
|
} |
|
|
|
/* |
|
* Spawn the kthreads that handle RCU's grace periods. |
|
*/ |
|
static int __init rcu_spawn_gp_kthread(void) |
|
{ |
|
unsigned long flags; |
|
int kthread_prio_in = kthread_prio; |
|
struct rcu_node *rnp; |
|
struct sched_param sp; |
|
struct task_struct *t; |
|
|
|
/* Force priority into range. */ |
|
if (IS_ENABLED(CONFIG_RCU_BOOST) && kthread_prio < 2 |
|
&& IS_BUILTIN(CONFIG_RCU_TORTURE_TEST)) |
|
kthread_prio = 2; |
|
else if (IS_ENABLED(CONFIG_RCU_BOOST) && kthread_prio < 1) |
|
kthread_prio = 1; |
|
else if (kthread_prio < 0) |
|
kthread_prio = 0; |
|
else if (kthread_prio > 99) |
|
kthread_prio = 99; |
|
|
|
if (kthread_prio != kthread_prio_in) |
|
pr_alert("rcu_spawn_gp_kthread(): Limited prio to %d from %d\n", |
|
kthread_prio, kthread_prio_in); |
|
|
|
rcu_scheduler_fully_active = 1; |
|
t = kthread_create(rcu_gp_kthread, NULL, "%s", rcu_state.name); |
|
if (WARN_ONCE(IS_ERR(t), "%s: Could not start grace-period kthread, OOM is now expected behavior\n", __func__)) |
|
return 0; |
|
if (kthread_prio) { |
|
sp.sched_priority = kthread_prio; |
|
sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); |
|
} |
|
rnp = rcu_get_root(); |
|
raw_spin_lock_irqsave_rcu_node(rnp, flags); |
|
WRITE_ONCE(rcu_state.gp_activity, jiffies); |
|
WRITE_ONCE(rcu_state.gp_req_activity, jiffies); |
|
// Reset .gp_activity and .gp_req_activity before setting .gp_kthread. |
|
smp_store_release(&rcu_state.gp_kthread, t); /* ^^^ */ |
|
raw_spin_unlock_irqrestore_rcu_node(rnp, flags); |
|
wake_up_process(t); |
|
rcu_spawn_nocb_kthreads(); |
|
rcu_spawn_boost_kthreads(); |
|
return 0; |
|
} |
|
early_initcall(rcu_spawn_gp_kthread); |
|
|
|
/* |
|
* This function is invoked towards the end of the scheduler's |
|
* initialization process. Before this is called, the idle task might |
|
* contain synchronous grace-period primitives (during which time, this idle |
|
* task is booting the system, and such primitives are no-ops). After this |
|
* function is called, any synchronous grace-period primitives are run as |
|
* expedited, with the requesting task driving the grace period forward. |
|
* A later core_initcall() rcu_set_runtime_mode() will switch to full |
|
* runtime RCU functionality. |
|
*/ |
|
void rcu_scheduler_starting(void) |
|
{ |
|
WARN_ON(num_online_cpus() != 1); |
|
WARN_ON(nr_context_switches() > 0); |
|
rcu_test_sync_prims(); |
|
rcu_scheduler_active = RCU_SCHEDULER_INIT; |
|
rcu_test_sync_prims(); |
|
} |
|
|
|
/* |
|
* Helper function for rcu_init() that initializes the rcu_state structure. |
|
*/ |
|
static void __init rcu_init_one(void) |
|
{ |
|
static const char * const buf[] = RCU_NODE_NAME_INIT; |
|
static const char * const fqs[] = RCU_FQS_NAME_INIT; |
|
static struct lock_class_key rcu_node_class[RCU_NUM_LVLS]; |
|
static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS]; |
|
|
|
int levelspread[RCU_NUM_LVLS]; /* kids/node in each level. */ |
|
int cpustride = 1; |
|
int i; |
|
int j; |
|
struct rcu_node *rnp; |
|
|
|
BUILD_BUG_ON(RCU_NUM_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */ |
|
|
|
/* Silence gcc 4.8 false positive about array index out of range. */ |
|
if (rcu_num_lvls <= 0 || rcu_num_lvls > RCU_NUM_LVLS) |
|
panic("rcu_init_one: rcu_num_lvls out of range"); |
|
|
|
/* Initialize the level-tracking arrays. */ |
|
|
|
for (i = 1; i < rcu_num_lvls; i++) |
|
rcu_state.level[i] = |
|
rcu_state.level[i - 1] + num_rcu_lvl[i - 1]; |
|
rcu_init_levelspread(levelspread, num_rcu_lvl); |
|
|
|
/* Initialize the elements themselves, starting from the leaves. */ |
|
|
|
for (i = rcu_num_lvls - 1; i >= 0; i--) { |
|
cpustride *= levelspread[i]; |
|
rnp = rcu_state.level[i]; |
|
for (j = 0; j < num_rcu_lvl[i]; j++, rnp++) { |
|
raw_spin_lock_init(&ACCESS_PRIVATE(rnp, lock)); |
|
lockdep_set_class_and_name(&ACCESS_PRIVATE(rnp, lock), |
|
&rcu_node_class[i], buf[i]); |
|
raw_spin_lock_init(&rnp->fqslock); |
|
lockdep_set_class_and_name(&rnp->fqslock, |
|
&rcu_fqs_class[i], fqs[i]); |
|
rnp->gp_seq = rcu_state.gp_seq; |
|
rnp->gp_seq_needed = rcu_state.gp_seq; |
|
rnp->completedqs = rcu_state.gp_seq; |
|
rnp->qsmask = 0; |
|
rnp->qsmaskinit = 0; |
|
rnp->grplo = j * cpustride; |
|
rnp->grphi = (j + 1) * cpustride - 1; |
|
if (rnp->grphi >= nr_cpu_ids) |
|
rnp->grphi = nr_cpu_ids - 1; |
|
if (i == 0) { |
|
rnp->grpnum = 0; |
|
rnp->grpmask = 0; |
|
rnp->parent = NULL; |
|
} else { |
|
rnp->grpnum = j % levelspread[i - 1]; |
|
rnp->grpmask = BIT(rnp->grpnum); |
|
rnp->parent = rcu_state.level[i - 1] + |
|
j / levelspread[i - 1]; |
|
} |
|
rnp->level = i; |
|
INIT_LIST_HEAD(&rnp->blkd_tasks); |
|
rcu_init_one_nocb(rnp); |
|
init_waitqueue_head(&rnp->exp_wq[0]); |
|
init_waitqueue_head(&rnp->exp_wq[1]); |
|
init_waitqueue_head(&rnp->exp_wq[2]); |
|
init_waitqueue_head(&rnp->exp_wq[3]); |
|
spin_lock_init(&rnp->exp_lock); |
|
} |
|
} |
|
|
|
init_swait_queue_head(&rcu_state.gp_wq); |
|
init_swait_queue_head(&rcu_state.expedited_wq); |
|
rnp = rcu_first_leaf_node(); |
|
for_each_possible_cpu(i) { |
|
while (i > rnp->grphi) |
|
rnp++; |
|
per_cpu_ptr(&rcu_data, i)->mynode = rnp; |
|
rcu_boot_init_percpu_data(i); |
|
} |
|
} |
|
|
|
/* |
|
* Compute the rcu_node tree geometry from kernel parameters. This cannot |
|
* replace the definitions in tree.h because those are needed to size |
|
* the ->node array in the rcu_state structure. |
|
*/ |
|
static void __init rcu_init_geometry(void) |
|
{ |
|
ulong d; |
|
int i; |
|
int rcu_capacity[RCU_NUM_LVLS]; |
|
|
|
/* |
|
* Initialize any unspecified boot parameters. |
|
* The default values of jiffies_till_first_fqs and |
|
* jiffies_till_next_fqs are set to the RCU_JIFFIES_TILL_FORCE_QS |
|
* value, which is a function of HZ, then adding one for each |
|
* RCU_JIFFIES_FQS_DIV CPUs that might be on the system. |
|
*/ |
|
d = RCU_JIFFIES_TILL_FORCE_QS + nr_cpu_ids / RCU_JIFFIES_FQS_DIV; |
|
if (jiffies_till_first_fqs == ULONG_MAX) |
|
jiffies_till_first_fqs = d; |
|
if (jiffies_till_next_fqs == ULONG_MAX) |
|
jiffies_till_next_fqs = d; |
|
adjust_jiffies_till_sched_qs(); |
|
|
|
/* If the compile-time values are accurate, just leave. */ |
|
if (rcu_fanout_leaf == RCU_FANOUT_LEAF && |
|
nr_cpu_ids == NR_CPUS) |
|
return; |
|
pr_info("Adjusting geometry for rcu_fanout_leaf=%d, nr_cpu_ids=%u\n", |
|
rcu_fanout_leaf, nr_cpu_ids); |
|
|
|
/* |
|
* The boot-time rcu_fanout_leaf parameter must be at least two |
|
* and cannot exceed the number of bits in the rcu_node masks. |
|
* Complain and fall back to the compile-time values if this |
|
* limit is exceeded. |
|
*/ |
|
if (rcu_fanout_leaf < 2 || |
|
rcu_fanout_leaf > sizeof(unsigned long) * 8) { |
|
rcu_fanout_leaf = RCU_FANOUT_LEAF; |
|
WARN_ON(1); |
|
return; |
|
} |
|
|
|
/* |
|
* Compute number of nodes that can be handled an rcu_node tree |
|
* with the given number of levels. |
|
*/ |
|
rcu_capacity[0] = rcu_fanout_leaf; |
|
for (i = 1; i < RCU_NUM_LVLS; i++) |
|
rcu_capacity[i] = rcu_capacity[i - 1] * RCU_FANOUT; |
|
|
|
/* |
|
* The tree must be able to accommodate the configured number of CPUs. |
|
* If this limit is exceeded, fall back to the compile-time values. |
|
*/ |
|
if (nr_cpu_ids > rcu_capacity[RCU_NUM_LVLS - 1]) { |
|
rcu_fanout_leaf = RCU_FANOUT_LEAF; |
|
WARN_ON(1); |
|
return; |
|
} |
|
|
|
/* Calculate the number of levels in the tree. */ |
|
for (i = 0; nr_cpu_ids > rcu_capacity[i]; i++) { |
|
} |
|
rcu_num_lvls = i + 1; |
|
|
|
/* Calculate the number of rcu_nodes at each level of the tree. */ |
|
for (i = 0; i < rcu_num_lvls; i++) { |
|
int cap = rcu_capacity[(rcu_num_lvls - 1) - i]; |
|
num_rcu_lvl[i] = DIV_ROUND_UP(nr_cpu_ids, cap); |
|
} |
|
|
|
/* Calculate the total number of rcu_node structures. */ |
|
rcu_num_nodes = 0; |
|
for (i = 0; i < rcu_num_lvls; i++) |
|
rcu_num_nodes += num_rcu_lvl[i]; |
|
} |
|
|
|
/* |
|
* Dump out the structure of the rcu_node combining tree associated |
|
* with the rcu_state structure. |
|
*/ |
|
static void __init rcu_dump_rcu_node_tree(void) |
|
{ |
|
int level = 0; |
|
struct rcu_node *rnp; |
|
|
|
pr_info("rcu_node tree layout dump\n"); |
|
pr_info(" "); |
|
rcu_for_each_node_breadth_first(rnp) { |
|
if (rnp->level != level) { |
|
pr_cont("\n"); |
|
pr_info(" "); |
|
level = rnp->level; |
|
} |
|
pr_cont("%d:%d ^%d ", rnp->grplo, rnp->grphi, rnp->grpnum); |
|
} |
|
pr_cont("\n"); |
|
} |
|
|
|
struct workqueue_struct *rcu_gp_wq; |
|
struct workqueue_struct *rcu_par_gp_wq; |
|
|
|
static void __init kfree_rcu_batch_init(void) |
|
{ |
|
int cpu; |
|
int i; |
|
|
|
for_each_possible_cpu(cpu) { |
|
struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu); |
|
|
|
for (i = 0; i < KFREE_N_BATCHES; i++) { |
|
INIT_RCU_WORK(&krcp->krw_arr[i].rcu_work, kfree_rcu_work); |
|
krcp->krw_arr[i].krcp = krcp; |
|
} |
|
|
|
INIT_DELAYED_WORK(&krcp->monitor_work, kfree_rcu_monitor); |
|
INIT_WORK(&krcp->page_cache_work, fill_page_cache_func); |
|
krcp->initialized = true; |
|
} |
|
if (register_shrinker(&kfree_rcu_shrinker)) |
|
pr_err("Failed to register kfree_rcu() shrinker!\n"); |
|
} |
|
|
|
void __init rcu_init(void) |
|
{ |
|
int cpu; |
|
|
|
rcu_early_boot_tests(); |
|
|
|
kfree_rcu_batch_init(); |
|
rcu_bootup_announce(); |
|
rcu_init_geometry(); |
|
rcu_init_one(); |
|
if (dump_tree) |
|
rcu_dump_rcu_node_tree(); |
|
if (use_softirq) |
|
open_softirq(RCU_SOFTIRQ, rcu_core_si); |
|
|
|
/* |
|
* We don't need protection against CPU-hotplug here because |
|
* this is called early in boot, before either interrupts |
|
* or the scheduler are operational. |
|
*/ |
|
pm_notifier(rcu_pm_notify, 0); |
|
for_each_online_cpu(cpu) { |
|
rcutree_prepare_cpu(cpu); |
|
rcu_cpu_starting(cpu); |
|
rcutree_online_cpu(cpu); |
|
} |
|
|
|
/* Create workqueue for expedited GPs and for Tree SRCU. */ |
|
rcu_gp_wq = alloc_workqueue("rcu_gp", WQ_MEM_RECLAIM, 0); |
|
WARN_ON(!rcu_gp_wq); |
|
rcu_par_gp_wq = alloc_workqueue("rcu_par_gp", WQ_MEM_RECLAIM, 0); |
|
WARN_ON(!rcu_par_gp_wq); |
|
srcu_init(); |
|
|
|
/* Fill in default value for rcutree.qovld boot parameter. */ |
|
/* -After- the rcu_node ->lock fields are initialized! */ |
|
if (qovld < 0) |
|
qovld_calc = DEFAULT_RCU_QOVLD_MULT * qhimark; |
|
else |
|
qovld_calc = qovld; |
|
} |
|
|
|
#include "tree_stall.h" |
|
#include "tree_exp.h" |
|
#include "tree_plugin.h"
|
|
|