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606 lines
18 KiB
606 lines
18 KiB
// SPDX-License-Identifier: GPL-2.0+ |
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/* |
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* Read-Copy Update mechanism for mutual exclusion |
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* |
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* Copyright IBM Corporation, 2001 |
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* |
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* Authors: Dipankar Sarma <[email protected]> |
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* Manfred Spraul <[email protected]> |
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* |
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* Based on the original work by Paul McKenney <[email protected]> |
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* and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. |
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* Papers: |
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* http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf |
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* http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001) |
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* |
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* For detailed explanation of Read-Copy Update mechanism see - |
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* http://lse.sourceforge.net/locking/rcupdate.html |
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* |
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*/ |
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#include <linux/types.h> |
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#include <linux/kernel.h> |
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#include <linux/init.h> |
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#include <linux/spinlock.h> |
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#include <linux/smp.h> |
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#include <linux/interrupt.h> |
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#include <linux/sched/signal.h> |
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#include <linux/sched/debug.h> |
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#include <linux/atomic.h> |
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#include <linux/bitops.h> |
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#include <linux/percpu.h> |
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#include <linux/notifier.h> |
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#include <linux/cpu.h> |
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#include <linux/mutex.h> |
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#include <linux/export.h> |
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#include <linux/hardirq.h> |
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#include <linux/delay.h> |
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#include <linux/moduleparam.h> |
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#include <linux/kthread.h> |
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#include <linux/tick.h> |
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#include <linux/rcupdate_wait.h> |
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#include <linux/sched/isolation.h> |
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#include <linux/kprobes.h> |
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#include <linux/slab.h> |
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#include <linux/irq_work.h> |
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#include <linux/rcupdate_trace.h> |
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#define CREATE_TRACE_POINTS |
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#include "rcu.h" |
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#ifdef MODULE_PARAM_PREFIX |
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#undef MODULE_PARAM_PREFIX |
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#endif |
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#define MODULE_PARAM_PREFIX "rcupdate." |
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|
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#ifndef CONFIG_TINY_RCU |
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module_param(rcu_expedited, int, 0); |
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module_param(rcu_normal, int, 0); |
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static int rcu_normal_after_boot = IS_ENABLED(CONFIG_PREEMPT_RT); |
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#ifndef CONFIG_PREEMPT_RT |
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module_param(rcu_normal_after_boot, int, 0); |
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#endif |
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#endif /* #ifndef CONFIG_TINY_RCU */ |
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#ifdef CONFIG_DEBUG_LOCK_ALLOC |
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/** |
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* rcu_read_lock_held_common() - might we be in RCU-sched read-side critical section? |
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* @ret: Best guess answer if lockdep cannot be relied on |
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* |
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* Returns true if lockdep must be ignored, in which case ``*ret`` contains |
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* the best guess described below. Otherwise returns false, in which |
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* case ``*ret`` tells the caller nothing and the caller should instead |
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* consult lockdep. |
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* |
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* If CONFIG_DEBUG_LOCK_ALLOC is selected, set ``*ret`` to nonzero iff in an |
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* RCU-sched read-side critical section. In absence of |
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* CONFIG_DEBUG_LOCK_ALLOC, this assumes we are in an RCU-sched read-side |
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* critical section unless it can prove otherwise. Note that disabling |
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* of preemption (including disabling irqs) counts as an RCU-sched |
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* read-side critical section. This is useful for debug checks in functions |
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* that required that they be called within an RCU-sched read-side |
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* critical section. |
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* |
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* Check debug_lockdep_rcu_enabled() to prevent false positives during boot |
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* and while lockdep is disabled. |
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* |
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* Note that if the CPU is in the idle loop from an RCU point of view (ie: |
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* that we are in the section between rcu_idle_enter() and rcu_idle_exit()) |
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* then rcu_read_lock_held() sets ``*ret`` to false even if the CPU did an |
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* rcu_read_lock(). The reason for this is that RCU ignores CPUs that are |
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* in such a section, considering these as in extended quiescent state, |
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* so such a CPU is effectively never in an RCU read-side critical section |
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* regardless of what RCU primitives it invokes. This state of affairs is |
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* required --- we need to keep an RCU-free window in idle where the CPU may |
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* possibly enter into low power mode. This way we can notice an extended |
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* quiescent state to other CPUs that started a grace period. Otherwise |
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* we would delay any grace period as long as we run in the idle task. |
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* |
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* Similarly, we avoid claiming an RCU read lock held if the current |
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* CPU is offline. |
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*/ |
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static bool rcu_read_lock_held_common(bool *ret) |
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{ |
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if (!debug_lockdep_rcu_enabled()) { |
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*ret = true; |
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return true; |
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} |
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if (!rcu_is_watching()) { |
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*ret = false; |
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return true; |
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} |
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if (!rcu_lockdep_current_cpu_online()) { |
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*ret = false; |
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return true; |
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} |
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return false; |
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} |
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int rcu_read_lock_sched_held(void) |
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{ |
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bool ret; |
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if (rcu_read_lock_held_common(&ret)) |
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return ret; |
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return lock_is_held(&rcu_sched_lock_map) || !preemptible(); |
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} |
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EXPORT_SYMBOL(rcu_read_lock_sched_held); |
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#endif |
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#ifndef CONFIG_TINY_RCU |
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/* |
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* Should expedited grace-period primitives always fall back to their |
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* non-expedited counterparts? Intended for use within RCU. Note |
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* that if the user specifies both rcu_expedited and rcu_normal, then |
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* rcu_normal wins. (Except during the time period during boot from |
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* when the first task is spawned until the rcu_set_runtime_mode() |
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* core_initcall() is invoked, at which point everything is expedited.) |
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*/ |
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bool rcu_gp_is_normal(void) |
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{ |
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return READ_ONCE(rcu_normal) && |
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rcu_scheduler_active != RCU_SCHEDULER_INIT; |
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} |
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EXPORT_SYMBOL_GPL(rcu_gp_is_normal); |
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static atomic_t rcu_expedited_nesting = ATOMIC_INIT(1); |
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/* |
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* Should normal grace-period primitives be expedited? Intended for |
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* use within RCU. Note that this function takes the rcu_expedited |
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* sysfs/boot variable and rcu_scheduler_active into account as well |
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* as the rcu_expedite_gp() nesting. So looping on rcu_unexpedite_gp() |
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* until rcu_gp_is_expedited() returns false is a -really- bad idea. |
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*/ |
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bool rcu_gp_is_expedited(void) |
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{ |
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return rcu_expedited || atomic_read(&rcu_expedited_nesting); |
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} |
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EXPORT_SYMBOL_GPL(rcu_gp_is_expedited); |
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/** |
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* rcu_expedite_gp - Expedite future RCU grace periods |
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* |
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* After a call to this function, future calls to synchronize_rcu() and |
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* friends act as the corresponding synchronize_rcu_expedited() function |
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* had instead been called. |
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*/ |
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void rcu_expedite_gp(void) |
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{ |
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atomic_inc(&rcu_expedited_nesting); |
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} |
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EXPORT_SYMBOL_GPL(rcu_expedite_gp); |
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/** |
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* rcu_unexpedite_gp - Cancel prior rcu_expedite_gp() invocation |
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* |
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* Undo a prior call to rcu_expedite_gp(). If all prior calls to |
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* rcu_expedite_gp() are undone by a subsequent call to rcu_unexpedite_gp(), |
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* and if the rcu_expedited sysfs/boot parameter is not set, then all |
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* subsequent calls to synchronize_rcu() and friends will return to |
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* their normal non-expedited behavior. |
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*/ |
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void rcu_unexpedite_gp(void) |
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{ |
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atomic_dec(&rcu_expedited_nesting); |
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} |
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EXPORT_SYMBOL_GPL(rcu_unexpedite_gp); |
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static bool rcu_boot_ended __read_mostly; |
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/* |
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* Inform RCU of the end of the in-kernel boot sequence. |
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*/ |
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void rcu_end_inkernel_boot(void) |
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{ |
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rcu_unexpedite_gp(); |
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if (rcu_normal_after_boot) |
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WRITE_ONCE(rcu_normal, 1); |
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rcu_boot_ended = true; |
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} |
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/* |
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* Let rcutorture know when it is OK to turn it up to eleven. |
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*/ |
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bool rcu_inkernel_boot_has_ended(void) |
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{ |
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return rcu_boot_ended; |
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} |
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EXPORT_SYMBOL_GPL(rcu_inkernel_boot_has_ended); |
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#endif /* #ifndef CONFIG_TINY_RCU */ |
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/* |
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* Test each non-SRCU synchronous grace-period wait API. This is |
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* useful just after a change in mode for these primitives, and |
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* during early boot. |
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*/ |
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void rcu_test_sync_prims(void) |
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{ |
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if (!IS_ENABLED(CONFIG_PROVE_RCU)) |
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return; |
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synchronize_rcu(); |
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synchronize_rcu_expedited(); |
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} |
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#if !defined(CONFIG_TINY_RCU) || defined(CONFIG_SRCU) |
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/* |
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* Switch to run-time mode once RCU has fully initialized. |
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*/ |
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static int __init rcu_set_runtime_mode(void) |
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{ |
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rcu_test_sync_prims(); |
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rcu_scheduler_active = RCU_SCHEDULER_RUNNING; |
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kfree_rcu_scheduler_running(); |
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rcu_test_sync_prims(); |
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return 0; |
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} |
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core_initcall(rcu_set_runtime_mode); |
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#endif /* #if !defined(CONFIG_TINY_RCU) || defined(CONFIG_SRCU) */ |
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#ifdef CONFIG_DEBUG_LOCK_ALLOC |
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static struct lock_class_key rcu_lock_key; |
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struct lockdep_map rcu_lock_map = { |
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.name = "rcu_read_lock", |
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.key = &rcu_lock_key, |
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.wait_type_outer = LD_WAIT_FREE, |
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.wait_type_inner = LD_WAIT_CONFIG, /* XXX PREEMPT_RCU ? */ |
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}; |
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EXPORT_SYMBOL_GPL(rcu_lock_map); |
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static struct lock_class_key rcu_bh_lock_key; |
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struct lockdep_map rcu_bh_lock_map = { |
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.name = "rcu_read_lock_bh", |
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.key = &rcu_bh_lock_key, |
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.wait_type_outer = LD_WAIT_FREE, |
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.wait_type_inner = LD_WAIT_CONFIG, /* PREEMPT_LOCK also makes BH preemptible */ |
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}; |
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EXPORT_SYMBOL_GPL(rcu_bh_lock_map); |
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static struct lock_class_key rcu_sched_lock_key; |
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struct lockdep_map rcu_sched_lock_map = { |
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.name = "rcu_read_lock_sched", |
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.key = &rcu_sched_lock_key, |
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.wait_type_outer = LD_WAIT_FREE, |
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.wait_type_inner = LD_WAIT_SPIN, |
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}; |
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EXPORT_SYMBOL_GPL(rcu_sched_lock_map); |
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// Tell lockdep when RCU callbacks are being invoked. |
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static struct lock_class_key rcu_callback_key; |
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struct lockdep_map rcu_callback_map = |
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STATIC_LOCKDEP_MAP_INIT("rcu_callback", &rcu_callback_key); |
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EXPORT_SYMBOL_GPL(rcu_callback_map); |
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noinstr int notrace debug_lockdep_rcu_enabled(void) |
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{ |
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return rcu_scheduler_active != RCU_SCHEDULER_INACTIVE && READ_ONCE(debug_locks) && |
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current->lockdep_recursion == 0; |
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} |
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EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled); |
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/** |
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* rcu_read_lock_held() - might we be in RCU read-side critical section? |
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* |
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* If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an RCU |
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* read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC, |
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* this assumes we are in an RCU read-side critical section unless it can |
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* prove otherwise. This is useful for debug checks in functions that |
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* require that they be called within an RCU read-side critical section. |
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* |
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* Checks debug_lockdep_rcu_enabled() to prevent false positives during boot |
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* and while lockdep is disabled. |
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* |
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* Note that rcu_read_lock() and the matching rcu_read_unlock() must |
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* occur in the same context, for example, it is illegal to invoke |
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* rcu_read_unlock() in process context if the matching rcu_read_lock() |
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* was invoked from within an irq handler. |
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* |
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* Note that rcu_read_lock() is disallowed if the CPU is either idle or |
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* offline from an RCU perspective, so check for those as well. |
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*/ |
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int rcu_read_lock_held(void) |
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{ |
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bool ret; |
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if (rcu_read_lock_held_common(&ret)) |
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return ret; |
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return lock_is_held(&rcu_lock_map); |
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} |
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EXPORT_SYMBOL_GPL(rcu_read_lock_held); |
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/** |
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* rcu_read_lock_bh_held() - might we be in RCU-bh read-side critical section? |
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* |
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* Check for bottom half being disabled, which covers both the |
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* CONFIG_PROVE_RCU and not cases. Note that if someone uses |
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* rcu_read_lock_bh(), but then later enables BH, lockdep (if enabled) |
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* will show the situation. This is useful for debug checks in functions |
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* that require that they be called within an RCU read-side critical |
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* section. |
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* |
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* Check debug_lockdep_rcu_enabled() to prevent false positives during boot. |
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* |
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* Note that rcu_read_lock_bh() is disallowed if the CPU is either idle or |
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* offline from an RCU perspective, so check for those as well. |
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*/ |
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int rcu_read_lock_bh_held(void) |
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{ |
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bool ret; |
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if (rcu_read_lock_held_common(&ret)) |
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return ret; |
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return in_softirq() || irqs_disabled(); |
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} |
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EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held); |
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int rcu_read_lock_any_held(void) |
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{ |
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bool ret; |
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if (rcu_read_lock_held_common(&ret)) |
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return ret; |
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if (lock_is_held(&rcu_lock_map) || |
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lock_is_held(&rcu_bh_lock_map) || |
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lock_is_held(&rcu_sched_lock_map)) |
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return 1; |
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return !preemptible(); |
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} |
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EXPORT_SYMBOL_GPL(rcu_read_lock_any_held); |
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#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
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/** |
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* wakeme_after_rcu() - Callback function to awaken a task after grace period |
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* @head: Pointer to rcu_head member within rcu_synchronize structure |
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* |
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* Awaken the corresponding task now that a grace period has elapsed. |
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*/ |
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void wakeme_after_rcu(struct rcu_head *head) |
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{ |
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struct rcu_synchronize *rcu; |
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rcu = container_of(head, struct rcu_synchronize, head); |
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complete(&rcu->completion); |
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} |
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EXPORT_SYMBOL_GPL(wakeme_after_rcu); |
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void __wait_rcu_gp(bool checktiny, int n, call_rcu_func_t *crcu_array, |
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struct rcu_synchronize *rs_array) |
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{ |
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int i; |
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int j; |
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/* Initialize and register callbacks for each crcu_array element. */ |
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for (i = 0; i < n; i++) { |
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if (checktiny && |
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(crcu_array[i] == call_rcu)) { |
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might_sleep(); |
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continue; |
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} |
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for (j = 0; j < i; j++) |
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if (crcu_array[j] == crcu_array[i]) |
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break; |
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if (j == i) { |
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init_rcu_head_on_stack(&rs_array[i].head); |
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init_completion(&rs_array[i].completion); |
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(crcu_array[i])(&rs_array[i].head, wakeme_after_rcu); |
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} |
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} |
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/* Wait for all callbacks to be invoked. */ |
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for (i = 0; i < n; i++) { |
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if (checktiny && |
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(crcu_array[i] == call_rcu)) |
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continue; |
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for (j = 0; j < i; j++) |
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if (crcu_array[j] == crcu_array[i]) |
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break; |
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if (j == i) { |
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wait_for_completion(&rs_array[i].completion); |
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destroy_rcu_head_on_stack(&rs_array[i].head); |
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} |
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} |
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} |
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EXPORT_SYMBOL_GPL(__wait_rcu_gp); |
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#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD |
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void init_rcu_head(struct rcu_head *head) |
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{ |
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debug_object_init(head, &rcuhead_debug_descr); |
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} |
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EXPORT_SYMBOL_GPL(init_rcu_head); |
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void destroy_rcu_head(struct rcu_head *head) |
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{ |
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debug_object_free(head, &rcuhead_debug_descr); |
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} |
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EXPORT_SYMBOL_GPL(destroy_rcu_head); |
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static bool rcuhead_is_static_object(void *addr) |
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{ |
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return true; |
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} |
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/** |
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* init_rcu_head_on_stack() - initialize on-stack rcu_head for debugobjects |
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* @head: pointer to rcu_head structure to be initialized |
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* |
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* This function informs debugobjects of a new rcu_head structure that |
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* has been allocated as an auto variable on the stack. This function |
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* is not required for rcu_head structures that are statically defined or |
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* that are dynamically allocated on the heap. This function has no |
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* effect for !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds. |
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*/ |
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void init_rcu_head_on_stack(struct rcu_head *head) |
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{ |
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debug_object_init_on_stack(head, &rcuhead_debug_descr); |
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} |
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EXPORT_SYMBOL_GPL(init_rcu_head_on_stack); |
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/** |
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* destroy_rcu_head_on_stack() - destroy on-stack rcu_head for debugobjects |
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* @head: pointer to rcu_head structure to be initialized |
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* |
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* This function informs debugobjects that an on-stack rcu_head structure |
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* is about to go out of scope. As with init_rcu_head_on_stack(), this |
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* function is not required for rcu_head structures that are statically |
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* defined or that are dynamically allocated on the heap. Also as with |
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* init_rcu_head_on_stack(), this function has no effect for |
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* !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds. |
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*/ |
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void destroy_rcu_head_on_stack(struct rcu_head *head) |
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{ |
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debug_object_free(head, &rcuhead_debug_descr); |
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} |
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EXPORT_SYMBOL_GPL(destroy_rcu_head_on_stack); |
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const struct debug_obj_descr rcuhead_debug_descr = { |
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.name = "rcu_head", |
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.is_static_object = rcuhead_is_static_object, |
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}; |
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EXPORT_SYMBOL_GPL(rcuhead_debug_descr); |
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#endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */ |
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#if defined(CONFIG_TREE_RCU) || defined(CONFIG_RCU_TRACE) |
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void do_trace_rcu_torture_read(const char *rcutorturename, struct rcu_head *rhp, |
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unsigned long secs, |
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unsigned long c_old, unsigned long c) |
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{ |
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trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c); |
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} |
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EXPORT_SYMBOL_GPL(do_trace_rcu_torture_read); |
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#else |
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#define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \ |
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do { } while (0) |
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#endif |
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#if IS_ENABLED(CONFIG_RCU_TORTURE_TEST) || IS_MODULE(CONFIG_RCU_TORTURE_TEST) |
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/* Get rcutorture access to sched_setaffinity(). */ |
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long rcutorture_sched_setaffinity(pid_t pid, const struct cpumask *in_mask) |
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{ |
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int ret; |
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ret = sched_setaffinity(pid, in_mask); |
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WARN_ONCE(ret, "%s: sched_setaffinity() returned %d\n", __func__, ret); |
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return ret; |
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} |
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EXPORT_SYMBOL_GPL(rcutorture_sched_setaffinity); |
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#endif |
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#ifdef CONFIG_RCU_STALL_COMMON |
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int rcu_cpu_stall_ftrace_dump __read_mostly; |
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module_param(rcu_cpu_stall_ftrace_dump, int, 0644); |
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int rcu_cpu_stall_suppress __read_mostly; // !0 = suppress stall warnings. |
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EXPORT_SYMBOL_GPL(rcu_cpu_stall_suppress); |
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module_param(rcu_cpu_stall_suppress, int, 0644); |
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int rcu_cpu_stall_timeout __read_mostly = CONFIG_RCU_CPU_STALL_TIMEOUT; |
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module_param(rcu_cpu_stall_timeout, int, 0644); |
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#endif /* #ifdef CONFIG_RCU_STALL_COMMON */ |
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// Suppress boot-time RCU CPU stall warnings and rcutorture writer stall |
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// warnings. Also used by rcutorture even if stall warnings are excluded. |
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int rcu_cpu_stall_suppress_at_boot __read_mostly; // !0 = suppress boot stalls. |
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EXPORT_SYMBOL_GPL(rcu_cpu_stall_suppress_at_boot); |
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module_param(rcu_cpu_stall_suppress_at_boot, int, 0444); |
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#ifdef CONFIG_PROVE_RCU |
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/* |
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* Early boot self test parameters. |
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*/ |
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static bool rcu_self_test; |
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module_param(rcu_self_test, bool, 0444); |
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|
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static int rcu_self_test_counter; |
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|
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static void test_callback(struct rcu_head *r) |
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{ |
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rcu_self_test_counter++; |
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pr_info("RCU test callback executed %d\n", rcu_self_test_counter); |
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} |
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|
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DEFINE_STATIC_SRCU(early_srcu); |
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static unsigned long early_srcu_cookie; |
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|
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struct early_boot_kfree_rcu { |
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struct rcu_head rh; |
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}; |
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|
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static void early_boot_test_call_rcu(void) |
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{ |
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static struct rcu_head head; |
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static struct rcu_head shead; |
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struct early_boot_kfree_rcu *rhp; |
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|
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call_rcu(&head, test_callback); |
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if (IS_ENABLED(CONFIG_SRCU)) { |
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early_srcu_cookie = start_poll_synchronize_srcu(&early_srcu); |
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call_srcu(&early_srcu, &shead, test_callback); |
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} |
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rhp = kmalloc(sizeof(*rhp), GFP_KERNEL); |
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if (!WARN_ON_ONCE(!rhp)) |
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kfree_rcu(rhp, rh); |
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} |
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|
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void rcu_early_boot_tests(void) |
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{ |
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pr_info("Running RCU self tests\n"); |
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|
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if (rcu_self_test) |
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early_boot_test_call_rcu(); |
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rcu_test_sync_prims(); |
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} |
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|
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static int rcu_verify_early_boot_tests(void) |
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{ |
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int ret = 0; |
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int early_boot_test_counter = 0; |
|
|
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if (rcu_self_test) { |
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early_boot_test_counter++; |
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rcu_barrier(); |
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if (IS_ENABLED(CONFIG_SRCU)) { |
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early_boot_test_counter++; |
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srcu_barrier(&early_srcu); |
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WARN_ON_ONCE(!poll_state_synchronize_srcu(&early_srcu, early_srcu_cookie)); |
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} |
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} |
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if (rcu_self_test_counter != early_boot_test_counter) { |
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WARN_ON(1); |
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ret = -1; |
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} |
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|
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return ret; |
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} |
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late_initcall(rcu_verify_early_boot_tests); |
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#else |
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void rcu_early_boot_tests(void) {} |
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#endif /* CONFIG_PROVE_RCU */ |
|
|
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#include "tasks.h" |
|
|
|
#ifndef CONFIG_TINY_RCU |
|
|
|
/* |
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* Print any significant non-default boot-time settings. |
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*/ |
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void __init rcupdate_announce_bootup_oddness(void) |
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{ |
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if (rcu_normal) |
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pr_info("\tNo expedited grace period (rcu_normal).\n"); |
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else if (rcu_normal_after_boot) |
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pr_info("\tNo expedited grace period (rcu_normal_after_boot).\n"); |
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else if (rcu_expedited) |
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pr_info("\tAll grace periods are expedited (rcu_expedited).\n"); |
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if (rcu_cpu_stall_suppress) |
|
pr_info("\tRCU CPU stall warnings suppressed (rcu_cpu_stall_suppress).\n"); |
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if (rcu_cpu_stall_timeout != CONFIG_RCU_CPU_STALL_TIMEOUT) |
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pr_info("\tRCU CPU stall warnings timeout set to %d (rcu_cpu_stall_timeout).\n", rcu_cpu_stall_timeout); |
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rcu_tasks_bootup_oddness(); |
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} |
|
|
|
#endif /* #ifndef CONFIG_TINY_RCU */
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