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998 lines
24 KiB
998 lines
24 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* linux/kernel/softirq.c |
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* |
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* Copyright (C) 1992 Linus Torvalds |
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* |
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* Rewritten. Old one was good in 2.2, but in 2.3 it was immoral. --ANK (990903) |
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*/ |
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|
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
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#include <linux/export.h> |
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#include <linux/kernel_stat.h> |
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#include <linux/interrupt.h> |
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#include <linux/init.h> |
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#include <linux/local_lock.h> |
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#include <linux/mm.h> |
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#include <linux/notifier.h> |
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#include <linux/percpu.h> |
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#include <linux/cpu.h> |
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#include <linux/freezer.h> |
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#include <linux/kthread.h> |
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#include <linux/rcupdate.h> |
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#include <linux/ftrace.h> |
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#include <linux/smp.h> |
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#include <linux/smpboot.h> |
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#include <linux/tick.h> |
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#include <linux/irq.h> |
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#include <linux/wait_bit.h> |
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#include <asm/softirq_stack.h> |
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#define CREATE_TRACE_POINTS |
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#include <trace/events/irq.h> |
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/* |
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- No shared variables, all the data are CPU local. |
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- If a softirq needs serialization, let it serialize itself |
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by its own spinlocks. |
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- Even if softirq is serialized, only local cpu is marked for |
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execution. Hence, we get something sort of weak cpu binding. |
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Though it is still not clear, will it result in better locality |
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or will not. |
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Examples: |
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- NET RX softirq. It is multithreaded and does not require |
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any global serialization. |
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- NET TX softirq. It kicks software netdevice queues, hence |
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it is logically serialized per device, but this serialization |
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is invisible to common code. |
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- Tasklets: serialized wrt itself. |
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*/ |
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#ifndef __ARCH_IRQ_STAT |
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DEFINE_PER_CPU_ALIGNED(irq_cpustat_t, irq_stat); |
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EXPORT_PER_CPU_SYMBOL(irq_stat); |
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#endif |
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static struct softirq_action softirq_vec[NR_SOFTIRQS] __cacheline_aligned_in_smp; |
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DEFINE_PER_CPU(struct task_struct *, ksoftirqd); |
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const char * const softirq_to_name[NR_SOFTIRQS] = { |
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"HI", "TIMER", "NET_TX", "NET_RX", "BLOCK", "IRQ_POLL", |
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"TASKLET", "SCHED", "HRTIMER", "RCU" |
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}; |
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/* |
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* we cannot loop indefinitely here to avoid userspace starvation, |
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* but we also don't want to introduce a worst case 1/HZ latency |
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* to the pending events, so lets the scheduler to balance |
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* the softirq load for us. |
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*/ |
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static void wakeup_softirqd(void) |
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{ |
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/* Interrupts are disabled: no need to stop preemption */ |
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struct task_struct *tsk = __this_cpu_read(ksoftirqd); |
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if (tsk) |
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wake_up_process(tsk); |
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} |
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/* |
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* If ksoftirqd is scheduled, we do not want to process pending softirqs |
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* right now. Let ksoftirqd handle this at its own rate, to get fairness, |
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* unless we're doing some of the synchronous softirqs. |
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*/ |
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#define SOFTIRQ_NOW_MASK ((1 << HI_SOFTIRQ) | (1 << TASKLET_SOFTIRQ)) |
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static bool ksoftirqd_running(unsigned long pending) |
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{ |
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struct task_struct *tsk = __this_cpu_read(ksoftirqd); |
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if (pending & SOFTIRQ_NOW_MASK) |
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return false; |
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return tsk && task_is_running(tsk) && !__kthread_should_park(tsk); |
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} |
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#ifdef CONFIG_TRACE_IRQFLAGS |
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DEFINE_PER_CPU(int, hardirqs_enabled); |
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DEFINE_PER_CPU(int, hardirq_context); |
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EXPORT_PER_CPU_SYMBOL_GPL(hardirqs_enabled); |
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EXPORT_PER_CPU_SYMBOL_GPL(hardirq_context); |
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#endif |
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/* |
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* SOFTIRQ_OFFSET usage: |
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* |
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* On !RT kernels 'count' is the preempt counter, on RT kernels this applies |
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* to a per CPU counter and to task::softirqs_disabled_cnt. |
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* |
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* - count is changed by SOFTIRQ_OFFSET on entering or leaving softirq |
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* processing. |
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* |
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* - count is changed by SOFTIRQ_DISABLE_OFFSET (= 2 * SOFTIRQ_OFFSET) |
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* on local_bh_disable or local_bh_enable. |
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* |
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* This lets us distinguish between whether we are currently processing |
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* softirq and whether we just have bh disabled. |
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*/ |
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#ifdef CONFIG_PREEMPT_RT |
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/* |
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* RT accounts for BH disabled sections in task::softirqs_disabled_cnt and |
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* also in per CPU softirq_ctrl::cnt. This is necessary to allow tasks in a |
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* softirq disabled section to be preempted. |
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* |
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* The per task counter is used for softirq_count(), in_softirq() and |
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* in_serving_softirqs() because these counts are only valid when the task |
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* holding softirq_ctrl::lock is running. |
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* |
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* The per CPU counter prevents pointless wakeups of ksoftirqd in case that |
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* the task which is in a softirq disabled section is preempted or blocks. |
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*/ |
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struct softirq_ctrl { |
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local_lock_t lock; |
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int cnt; |
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}; |
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static DEFINE_PER_CPU(struct softirq_ctrl, softirq_ctrl) = { |
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.lock = INIT_LOCAL_LOCK(softirq_ctrl.lock), |
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}; |
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/** |
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* local_bh_blocked() - Check for idle whether BH processing is blocked |
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* |
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* Returns false if the per CPU softirq::cnt is 0 otherwise true. |
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* |
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* This is invoked from the idle task to guard against false positive |
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* softirq pending warnings, which would happen when the task which holds |
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* softirq_ctrl::lock was the only running task on the CPU and blocks on |
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* some other lock. |
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*/ |
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bool local_bh_blocked(void) |
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{ |
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return __this_cpu_read(softirq_ctrl.cnt) != 0; |
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} |
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void __local_bh_disable_ip(unsigned long ip, unsigned int cnt) |
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{ |
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unsigned long flags; |
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int newcnt; |
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WARN_ON_ONCE(in_hardirq()); |
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/* First entry of a task into a BH disabled section? */ |
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if (!current->softirq_disable_cnt) { |
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if (preemptible()) { |
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local_lock(&softirq_ctrl.lock); |
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/* Required to meet the RCU bottomhalf requirements. */ |
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rcu_read_lock(); |
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} else { |
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DEBUG_LOCKS_WARN_ON(this_cpu_read(softirq_ctrl.cnt)); |
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} |
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} |
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/* |
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* Track the per CPU softirq disabled state. On RT this is per CPU |
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* state to allow preemption of bottom half disabled sections. |
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*/ |
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newcnt = __this_cpu_add_return(softirq_ctrl.cnt, cnt); |
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/* |
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* Reflect the result in the task state to prevent recursion on the |
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* local lock and to make softirq_count() & al work. |
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*/ |
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current->softirq_disable_cnt = newcnt; |
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if (IS_ENABLED(CONFIG_TRACE_IRQFLAGS) && newcnt == cnt) { |
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raw_local_irq_save(flags); |
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lockdep_softirqs_off(ip); |
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raw_local_irq_restore(flags); |
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} |
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} |
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EXPORT_SYMBOL(__local_bh_disable_ip); |
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static void __local_bh_enable(unsigned int cnt, bool unlock) |
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{ |
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unsigned long flags; |
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int newcnt; |
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DEBUG_LOCKS_WARN_ON(current->softirq_disable_cnt != |
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this_cpu_read(softirq_ctrl.cnt)); |
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if (IS_ENABLED(CONFIG_TRACE_IRQFLAGS) && softirq_count() == cnt) { |
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raw_local_irq_save(flags); |
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lockdep_softirqs_on(_RET_IP_); |
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raw_local_irq_restore(flags); |
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} |
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newcnt = __this_cpu_sub_return(softirq_ctrl.cnt, cnt); |
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current->softirq_disable_cnt = newcnt; |
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if (!newcnt && unlock) { |
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rcu_read_unlock(); |
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local_unlock(&softirq_ctrl.lock); |
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} |
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} |
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void __local_bh_enable_ip(unsigned long ip, unsigned int cnt) |
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{ |
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bool preempt_on = preemptible(); |
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unsigned long flags; |
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u32 pending; |
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int curcnt; |
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WARN_ON_ONCE(in_irq()); |
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lockdep_assert_irqs_enabled(); |
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local_irq_save(flags); |
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curcnt = __this_cpu_read(softirq_ctrl.cnt); |
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/* |
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* If this is not reenabling soft interrupts, no point in trying to |
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* run pending ones. |
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*/ |
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if (curcnt != cnt) |
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goto out; |
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pending = local_softirq_pending(); |
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if (!pending || ksoftirqd_running(pending)) |
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goto out; |
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/* |
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* If this was called from non preemptible context, wake up the |
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* softirq daemon. |
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*/ |
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if (!preempt_on) { |
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wakeup_softirqd(); |
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goto out; |
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} |
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/* |
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* Adjust softirq count to SOFTIRQ_OFFSET which makes |
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* in_serving_softirq() become true. |
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*/ |
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cnt = SOFTIRQ_OFFSET; |
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__local_bh_enable(cnt, false); |
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__do_softirq(); |
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out: |
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__local_bh_enable(cnt, preempt_on); |
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local_irq_restore(flags); |
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} |
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EXPORT_SYMBOL(__local_bh_enable_ip); |
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/* |
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* Invoked from ksoftirqd_run() outside of the interrupt disabled section |
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* to acquire the per CPU local lock for reentrancy protection. |
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*/ |
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static inline void ksoftirqd_run_begin(void) |
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{ |
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__local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET); |
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local_irq_disable(); |
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} |
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/* Counterpart to ksoftirqd_run_begin() */ |
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static inline void ksoftirqd_run_end(void) |
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{ |
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__local_bh_enable(SOFTIRQ_OFFSET, true); |
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WARN_ON_ONCE(in_interrupt()); |
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local_irq_enable(); |
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} |
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static inline void softirq_handle_begin(void) { } |
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static inline void softirq_handle_end(void) { } |
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static inline bool should_wake_ksoftirqd(void) |
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{ |
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return !this_cpu_read(softirq_ctrl.cnt); |
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} |
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static inline void invoke_softirq(void) |
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{ |
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if (should_wake_ksoftirqd()) |
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wakeup_softirqd(); |
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} |
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#else /* CONFIG_PREEMPT_RT */ |
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/* |
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* This one is for softirq.c-internal use, where hardirqs are disabled |
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* legitimately: |
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*/ |
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#ifdef CONFIG_TRACE_IRQFLAGS |
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void __local_bh_disable_ip(unsigned long ip, unsigned int cnt) |
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{ |
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unsigned long flags; |
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WARN_ON_ONCE(in_irq()); |
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raw_local_irq_save(flags); |
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/* |
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* The preempt tracer hooks into preempt_count_add and will break |
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* lockdep because it calls back into lockdep after SOFTIRQ_OFFSET |
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* is set and before current->softirq_enabled is cleared. |
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* We must manually increment preempt_count here and manually |
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* call the trace_preempt_off later. |
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*/ |
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__preempt_count_add(cnt); |
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/* |
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* Were softirqs turned off above: |
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*/ |
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if (softirq_count() == (cnt & SOFTIRQ_MASK)) |
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lockdep_softirqs_off(ip); |
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raw_local_irq_restore(flags); |
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if (preempt_count() == cnt) { |
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#ifdef CONFIG_DEBUG_PREEMPT |
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current->preempt_disable_ip = get_lock_parent_ip(); |
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#endif |
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trace_preempt_off(CALLER_ADDR0, get_lock_parent_ip()); |
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} |
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} |
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EXPORT_SYMBOL(__local_bh_disable_ip); |
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#endif /* CONFIG_TRACE_IRQFLAGS */ |
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static void __local_bh_enable(unsigned int cnt) |
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{ |
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lockdep_assert_irqs_disabled(); |
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if (preempt_count() == cnt) |
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trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip()); |
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if (softirq_count() == (cnt & SOFTIRQ_MASK)) |
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lockdep_softirqs_on(_RET_IP_); |
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__preempt_count_sub(cnt); |
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} |
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/* |
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* Special-case - softirqs can safely be enabled by __do_softirq(), |
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* without processing still-pending softirqs: |
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*/ |
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void _local_bh_enable(void) |
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{ |
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WARN_ON_ONCE(in_irq()); |
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__local_bh_enable(SOFTIRQ_DISABLE_OFFSET); |
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} |
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EXPORT_SYMBOL(_local_bh_enable); |
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void __local_bh_enable_ip(unsigned long ip, unsigned int cnt) |
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{ |
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WARN_ON_ONCE(in_irq()); |
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lockdep_assert_irqs_enabled(); |
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#ifdef CONFIG_TRACE_IRQFLAGS |
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local_irq_disable(); |
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#endif |
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/* |
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* Are softirqs going to be turned on now: |
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*/ |
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if (softirq_count() == SOFTIRQ_DISABLE_OFFSET) |
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lockdep_softirqs_on(ip); |
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/* |
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* Keep preemption disabled until we are done with |
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* softirq processing: |
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*/ |
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__preempt_count_sub(cnt - 1); |
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if (unlikely(!in_interrupt() && local_softirq_pending())) { |
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/* |
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* Run softirq if any pending. And do it in its own stack |
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* as we may be calling this deep in a task call stack already. |
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*/ |
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do_softirq(); |
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} |
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preempt_count_dec(); |
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#ifdef CONFIG_TRACE_IRQFLAGS |
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local_irq_enable(); |
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#endif |
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preempt_check_resched(); |
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} |
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EXPORT_SYMBOL(__local_bh_enable_ip); |
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static inline void softirq_handle_begin(void) |
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{ |
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__local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET); |
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} |
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static inline void softirq_handle_end(void) |
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{ |
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__local_bh_enable(SOFTIRQ_OFFSET); |
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WARN_ON_ONCE(in_interrupt()); |
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} |
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static inline void ksoftirqd_run_begin(void) |
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{ |
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local_irq_disable(); |
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} |
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static inline void ksoftirqd_run_end(void) |
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{ |
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local_irq_enable(); |
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} |
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static inline bool should_wake_ksoftirqd(void) |
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{ |
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return true; |
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} |
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static inline void invoke_softirq(void) |
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{ |
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if (ksoftirqd_running(local_softirq_pending())) |
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return; |
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if (!force_irqthreads() || !__this_cpu_read(ksoftirqd)) { |
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#ifdef CONFIG_HAVE_IRQ_EXIT_ON_IRQ_STACK |
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/* |
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* We can safely execute softirq on the current stack if |
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* it is the irq stack, because it should be near empty |
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* at this stage. |
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*/ |
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__do_softirq(); |
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#else |
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/* |
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* Otherwise, irq_exit() is called on the task stack that can |
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* be potentially deep already. So call softirq in its own stack |
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* to prevent from any overrun. |
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*/ |
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do_softirq_own_stack(); |
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#endif |
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} else { |
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wakeup_softirqd(); |
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} |
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} |
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asmlinkage __visible void do_softirq(void) |
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{ |
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__u32 pending; |
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unsigned long flags; |
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if (in_interrupt()) |
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return; |
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local_irq_save(flags); |
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pending = local_softirq_pending(); |
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if (pending && !ksoftirqd_running(pending)) |
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do_softirq_own_stack(); |
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local_irq_restore(flags); |
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} |
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#endif /* !CONFIG_PREEMPT_RT */ |
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/* |
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* We restart softirq processing for at most MAX_SOFTIRQ_RESTART times, |
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* but break the loop if need_resched() is set or after 2 ms. |
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* The MAX_SOFTIRQ_TIME provides a nice upper bound in most cases, but in |
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* certain cases, such as stop_machine(), jiffies may cease to |
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* increment and so we need the MAX_SOFTIRQ_RESTART limit as |
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* well to make sure we eventually return from this method. |
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* |
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* These limits have been established via experimentation. |
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* The two things to balance is latency against fairness - |
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* we want to handle softirqs as soon as possible, but they |
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* should not be able to lock up the box. |
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*/ |
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#define MAX_SOFTIRQ_TIME msecs_to_jiffies(2) |
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#define MAX_SOFTIRQ_RESTART 10 |
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#ifdef CONFIG_TRACE_IRQFLAGS |
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/* |
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* When we run softirqs from irq_exit() and thus on the hardirq stack we need |
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* to keep the lockdep irq context tracking as tight as possible in order to |
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* not miss-qualify lock contexts and miss possible deadlocks. |
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*/ |
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static inline bool lockdep_softirq_start(void) |
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{ |
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bool in_hardirq = false; |
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if (lockdep_hardirq_context()) { |
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in_hardirq = true; |
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lockdep_hardirq_exit(); |
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} |
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lockdep_softirq_enter(); |
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return in_hardirq; |
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} |
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static inline void lockdep_softirq_end(bool in_hardirq) |
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{ |
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lockdep_softirq_exit(); |
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if (in_hardirq) |
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lockdep_hardirq_enter(); |
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} |
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#else |
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static inline bool lockdep_softirq_start(void) { return false; } |
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static inline void lockdep_softirq_end(bool in_hardirq) { } |
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#endif |
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asmlinkage __visible void __softirq_entry __do_softirq(void) |
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{ |
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unsigned long end = jiffies + MAX_SOFTIRQ_TIME; |
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unsigned long old_flags = current->flags; |
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int max_restart = MAX_SOFTIRQ_RESTART; |
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struct softirq_action *h; |
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bool in_hardirq; |
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__u32 pending; |
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int softirq_bit; |
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/* |
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* Mask out PF_MEMALLOC as the current task context is borrowed for the |
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* softirq. A softirq handled, such as network RX, might set PF_MEMALLOC |
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* again if the socket is related to swapping. |
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*/ |
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current->flags &= ~PF_MEMALLOC; |
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pending = local_softirq_pending(); |
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softirq_handle_begin(); |
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in_hardirq = lockdep_softirq_start(); |
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account_softirq_enter(current); |
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restart: |
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/* Reset the pending bitmask before enabling irqs */ |
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set_softirq_pending(0); |
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local_irq_enable(); |
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h = softirq_vec; |
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while ((softirq_bit = ffs(pending))) { |
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unsigned int vec_nr; |
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int prev_count; |
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h += softirq_bit - 1; |
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vec_nr = h - softirq_vec; |
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prev_count = preempt_count(); |
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kstat_incr_softirqs_this_cpu(vec_nr); |
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trace_softirq_entry(vec_nr); |
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h->action(h); |
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trace_softirq_exit(vec_nr); |
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if (unlikely(prev_count != preempt_count())) { |
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pr_err("huh, entered softirq %u %s %p with preempt_count %08x, exited with %08x?\n", |
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vec_nr, softirq_to_name[vec_nr], h->action, |
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prev_count, preempt_count()); |
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preempt_count_set(prev_count); |
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} |
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h++; |
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pending >>= softirq_bit; |
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} |
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if (!IS_ENABLED(CONFIG_PREEMPT_RT) && |
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__this_cpu_read(ksoftirqd) == current) |
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rcu_softirq_qs(); |
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local_irq_disable(); |
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pending = local_softirq_pending(); |
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if (pending) { |
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if (time_before(jiffies, end) && !need_resched() && |
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--max_restart) |
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goto restart; |
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wakeup_softirqd(); |
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} |
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account_softirq_exit(current); |
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lockdep_softirq_end(in_hardirq); |
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softirq_handle_end(); |
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current_restore_flags(old_flags, PF_MEMALLOC); |
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} |
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/** |
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* irq_enter_rcu - Enter an interrupt context with RCU watching |
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*/ |
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void irq_enter_rcu(void) |
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{ |
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__irq_enter_raw(); |
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if (is_idle_task(current) && (irq_count() == HARDIRQ_OFFSET)) |
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tick_irq_enter(); |
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account_hardirq_enter(current); |
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} |
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/** |
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* irq_enter - Enter an interrupt context including RCU update |
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*/ |
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void irq_enter(void) |
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{ |
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rcu_irq_enter(); |
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irq_enter_rcu(); |
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} |
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|
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static inline void tick_irq_exit(void) |
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{ |
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#ifdef CONFIG_NO_HZ_COMMON |
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int cpu = smp_processor_id(); |
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|
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/* Make sure that timer wheel updates are propagated */ |
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if ((idle_cpu(cpu) && !need_resched()) || tick_nohz_full_cpu(cpu)) { |
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if (!in_irq()) |
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tick_nohz_irq_exit(); |
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} |
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#endif |
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} |
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|
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static inline void __irq_exit_rcu(void) |
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{ |
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#ifndef __ARCH_IRQ_EXIT_IRQS_DISABLED |
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local_irq_disable(); |
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#else |
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lockdep_assert_irqs_disabled(); |
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#endif |
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account_hardirq_exit(current); |
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preempt_count_sub(HARDIRQ_OFFSET); |
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if (!in_interrupt() && local_softirq_pending()) |
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invoke_softirq(); |
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|
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tick_irq_exit(); |
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} |
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|
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/** |
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* irq_exit_rcu() - Exit an interrupt context without updating RCU |
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* |
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* Also processes softirqs if needed and possible. |
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*/ |
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void irq_exit_rcu(void) |
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{ |
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__irq_exit_rcu(); |
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/* must be last! */ |
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lockdep_hardirq_exit(); |
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} |
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|
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/** |
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* irq_exit - Exit an interrupt context, update RCU and lockdep |
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* |
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* Also processes softirqs if needed and possible. |
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*/ |
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void irq_exit(void) |
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{ |
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__irq_exit_rcu(); |
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rcu_irq_exit(); |
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/* must be last! */ |
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lockdep_hardirq_exit(); |
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} |
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|
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/* |
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* This function must run with irqs disabled! |
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*/ |
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inline void raise_softirq_irqoff(unsigned int nr) |
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{ |
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__raise_softirq_irqoff(nr); |
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|
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/* |
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* If we're in an interrupt or softirq, we're done |
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* (this also catches softirq-disabled code). We will |
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* actually run the softirq once we return from |
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* the irq or softirq. |
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* |
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* Otherwise we wake up ksoftirqd to make sure we |
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* schedule the softirq soon. |
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*/ |
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if (!in_interrupt() && should_wake_ksoftirqd()) |
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wakeup_softirqd(); |
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} |
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|
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void raise_softirq(unsigned int nr) |
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{ |
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unsigned long flags; |
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|
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local_irq_save(flags); |
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raise_softirq_irqoff(nr); |
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local_irq_restore(flags); |
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} |
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|
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void __raise_softirq_irqoff(unsigned int nr) |
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{ |
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lockdep_assert_irqs_disabled(); |
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trace_softirq_raise(nr); |
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or_softirq_pending(1UL << nr); |
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} |
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|
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void open_softirq(int nr, void (*action)(struct softirq_action *)) |
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{ |
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softirq_vec[nr].action = action; |
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} |
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|
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/* |
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* Tasklets |
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*/ |
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struct tasklet_head { |
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struct tasklet_struct *head; |
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struct tasklet_struct **tail; |
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}; |
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|
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static DEFINE_PER_CPU(struct tasklet_head, tasklet_vec); |
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static DEFINE_PER_CPU(struct tasklet_head, tasklet_hi_vec); |
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|
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static void __tasklet_schedule_common(struct tasklet_struct *t, |
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struct tasklet_head __percpu *headp, |
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unsigned int softirq_nr) |
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{ |
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struct tasklet_head *head; |
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unsigned long flags; |
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|
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local_irq_save(flags); |
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head = this_cpu_ptr(headp); |
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t->next = NULL; |
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*head->tail = t; |
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head->tail = &(t->next); |
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raise_softirq_irqoff(softirq_nr); |
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local_irq_restore(flags); |
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} |
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|
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void __tasklet_schedule(struct tasklet_struct *t) |
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{ |
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__tasklet_schedule_common(t, &tasklet_vec, |
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TASKLET_SOFTIRQ); |
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} |
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EXPORT_SYMBOL(__tasklet_schedule); |
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|
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void __tasklet_hi_schedule(struct tasklet_struct *t) |
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{ |
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__tasklet_schedule_common(t, &tasklet_hi_vec, |
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HI_SOFTIRQ); |
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} |
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EXPORT_SYMBOL(__tasklet_hi_schedule); |
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|
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static bool tasklet_clear_sched(struct tasklet_struct *t) |
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{ |
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if (test_and_clear_bit(TASKLET_STATE_SCHED, &t->state)) { |
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wake_up_var(&t->state); |
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return true; |
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} |
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|
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WARN_ONCE(1, "tasklet SCHED state not set: %s %pS\n", |
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t->use_callback ? "callback" : "func", |
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t->use_callback ? (void *)t->callback : (void *)t->func); |
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|
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return false; |
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} |
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|
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static void tasklet_action_common(struct softirq_action *a, |
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struct tasklet_head *tl_head, |
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unsigned int softirq_nr) |
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{ |
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struct tasklet_struct *list; |
|
|
|
local_irq_disable(); |
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list = tl_head->head; |
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tl_head->head = NULL; |
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tl_head->tail = &tl_head->head; |
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local_irq_enable(); |
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|
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while (list) { |
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struct tasklet_struct *t = list; |
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|
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list = list->next; |
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|
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if (tasklet_trylock(t)) { |
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if (!atomic_read(&t->count)) { |
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if (tasklet_clear_sched(t)) { |
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if (t->use_callback) |
|
t->callback(t); |
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else |
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t->func(t->data); |
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} |
|
tasklet_unlock(t); |
|
continue; |
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} |
|
tasklet_unlock(t); |
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} |
|
|
|
local_irq_disable(); |
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t->next = NULL; |
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*tl_head->tail = t; |
|
tl_head->tail = &t->next; |
|
__raise_softirq_irqoff(softirq_nr); |
|
local_irq_enable(); |
|
} |
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} |
|
|
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static __latent_entropy void tasklet_action(struct softirq_action *a) |
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{ |
|
tasklet_action_common(a, this_cpu_ptr(&tasklet_vec), TASKLET_SOFTIRQ); |
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} |
|
|
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static __latent_entropy void tasklet_hi_action(struct softirq_action *a) |
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{ |
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tasklet_action_common(a, this_cpu_ptr(&tasklet_hi_vec), HI_SOFTIRQ); |
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} |
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|
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void tasklet_setup(struct tasklet_struct *t, |
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void (*callback)(struct tasklet_struct *)) |
|
{ |
|
t->next = NULL; |
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t->state = 0; |
|
atomic_set(&t->count, 0); |
|
t->callback = callback; |
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t->use_callback = true; |
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t->data = 0; |
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} |
|
EXPORT_SYMBOL(tasklet_setup); |
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|
|
void tasklet_init(struct tasklet_struct *t, |
|
void (*func)(unsigned long), unsigned long data) |
|
{ |
|
t->next = NULL; |
|
t->state = 0; |
|
atomic_set(&t->count, 0); |
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t->func = func; |
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t->use_callback = false; |
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t->data = data; |
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} |
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EXPORT_SYMBOL(tasklet_init); |
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|
|
#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT) |
|
/* |
|
* Do not use in new code. Waiting for tasklets from atomic contexts is |
|
* error prone and should be avoided. |
|
*/ |
|
void tasklet_unlock_spin_wait(struct tasklet_struct *t) |
|
{ |
|
while (test_bit(TASKLET_STATE_RUN, &(t)->state)) { |
|
if (IS_ENABLED(CONFIG_PREEMPT_RT)) { |
|
/* |
|
* Prevent a live lock when current preempted soft |
|
* interrupt processing or prevents ksoftirqd from |
|
* running. If the tasklet runs on a different CPU |
|
* then this has no effect other than doing the BH |
|
* disable/enable dance for nothing. |
|
*/ |
|
local_bh_disable(); |
|
local_bh_enable(); |
|
} else { |
|
cpu_relax(); |
|
} |
|
} |
|
} |
|
EXPORT_SYMBOL(tasklet_unlock_spin_wait); |
|
#endif |
|
|
|
void tasklet_kill(struct tasklet_struct *t) |
|
{ |
|
if (in_interrupt()) |
|
pr_notice("Attempt to kill tasklet from interrupt\n"); |
|
|
|
while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state)) |
|
wait_var_event(&t->state, !test_bit(TASKLET_STATE_SCHED, &t->state)); |
|
|
|
tasklet_unlock_wait(t); |
|
tasklet_clear_sched(t); |
|
} |
|
EXPORT_SYMBOL(tasklet_kill); |
|
|
|
#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT) |
|
void tasklet_unlock(struct tasklet_struct *t) |
|
{ |
|
smp_mb__before_atomic(); |
|
clear_bit(TASKLET_STATE_RUN, &t->state); |
|
smp_mb__after_atomic(); |
|
wake_up_var(&t->state); |
|
} |
|
EXPORT_SYMBOL_GPL(tasklet_unlock); |
|
|
|
void tasklet_unlock_wait(struct tasklet_struct *t) |
|
{ |
|
wait_var_event(&t->state, !test_bit(TASKLET_STATE_RUN, &t->state)); |
|
} |
|
EXPORT_SYMBOL_GPL(tasklet_unlock_wait); |
|
#endif |
|
|
|
void __init softirq_init(void) |
|
{ |
|
int cpu; |
|
|
|
for_each_possible_cpu(cpu) { |
|
per_cpu(tasklet_vec, cpu).tail = |
|
&per_cpu(tasklet_vec, cpu).head; |
|
per_cpu(tasklet_hi_vec, cpu).tail = |
|
&per_cpu(tasklet_hi_vec, cpu).head; |
|
} |
|
|
|
open_softirq(TASKLET_SOFTIRQ, tasklet_action); |
|
open_softirq(HI_SOFTIRQ, tasklet_hi_action); |
|
} |
|
|
|
static int ksoftirqd_should_run(unsigned int cpu) |
|
{ |
|
return local_softirq_pending(); |
|
} |
|
|
|
static void run_ksoftirqd(unsigned int cpu) |
|
{ |
|
ksoftirqd_run_begin(); |
|
if (local_softirq_pending()) { |
|
/* |
|
* We can safely run softirq on inline stack, as we are not deep |
|
* in the task stack here. |
|
*/ |
|
__do_softirq(); |
|
ksoftirqd_run_end(); |
|
cond_resched(); |
|
return; |
|
} |
|
ksoftirqd_run_end(); |
|
} |
|
|
|
#ifdef CONFIG_HOTPLUG_CPU |
|
static int takeover_tasklets(unsigned int cpu) |
|
{ |
|
/* CPU is dead, so no lock needed. */ |
|
local_irq_disable(); |
|
|
|
/* Find end, append list for that CPU. */ |
|
if (&per_cpu(tasklet_vec, cpu).head != per_cpu(tasklet_vec, cpu).tail) { |
|
*__this_cpu_read(tasklet_vec.tail) = per_cpu(tasklet_vec, cpu).head; |
|
__this_cpu_write(tasklet_vec.tail, per_cpu(tasklet_vec, cpu).tail); |
|
per_cpu(tasklet_vec, cpu).head = NULL; |
|
per_cpu(tasklet_vec, cpu).tail = &per_cpu(tasklet_vec, cpu).head; |
|
} |
|
raise_softirq_irqoff(TASKLET_SOFTIRQ); |
|
|
|
if (&per_cpu(tasklet_hi_vec, cpu).head != per_cpu(tasklet_hi_vec, cpu).tail) { |
|
*__this_cpu_read(tasklet_hi_vec.tail) = per_cpu(tasklet_hi_vec, cpu).head; |
|
__this_cpu_write(tasklet_hi_vec.tail, per_cpu(tasklet_hi_vec, cpu).tail); |
|
per_cpu(tasklet_hi_vec, cpu).head = NULL; |
|
per_cpu(tasklet_hi_vec, cpu).tail = &per_cpu(tasklet_hi_vec, cpu).head; |
|
} |
|
raise_softirq_irqoff(HI_SOFTIRQ); |
|
|
|
local_irq_enable(); |
|
return 0; |
|
} |
|
#else |
|
#define takeover_tasklets NULL |
|
#endif /* CONFIG_HOTPLUG_CPU */ |
|
|
|
static struct smp_hotplug_thread softirq_threads = { |
|
.store = &ksoftirqd, |
|
.thread_should_run = ksoftirqd_should_run, |
|
.thread_fn = run_ksoftirqd, |
|
.thread_comm = "ksoftirqd/%u", |
|
}; |
|
|
|
static __init int spawn_ksoftirqd(void) |
|
{ |
|
cpuhp_setup_state_nocalls(CPUHP_SOFTIRQ_DEAD, "softirq:dead", NULL, |
|
takeover_tasklets); |
|
BUG_ON(smpboot_register_percpu_thread(&softirq_threads)); |
|
|
|
return 0; |
|
} |
|
early_initcall(spawn_ksoftirqd); |
|
|
|
/* |
|
* [ These __weak aliases are kept in a separate compilation unit, so that |
|
* GCC does not inline them incorrectly. ] |
|
*/ |
|
|
|
int __init __weak early_irq_init(void) |
|
{ |
|
return 0; |
|
} |
|
|
|
int __init __weak arch_probe_nr_irqs(void) |
|
{ |
|
return NR_IRQS_LEGACY; |
|
} |
|
|
|
int __init __weak arch_early_irq_init(void) |
|
{ |
|
return 0; |
|
} |
|
|
|
unsigned int __weak arch_dynirq_lower_bound(unsigned int from) |
|
{ |
|
return from; |
|
}
|
|
|