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Copy pathirq_work.c
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342 lines (282 loc) · 8.06 KB
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// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2010 Red Hat, Inc., Peter Zijlstra
*
* Provides a framework for enqueueing and running callbacks from hardirq
* context. The enqueueing is NMI-safe.
*/
#include <linux/bug.h>
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/irq_work.h>
#include <linux/percpu.h>
#include <linux/hardirq.h>
#include <linux/irqflags.h>
#include <linux/sched.h>
#include <linux/tick.h>
#include <linux/cpu.h>
#include <linux/notifier.h>
#include <linux/smp.h>
#include <linux/smpboot.h>
#include <asm/processor.h>
#include <linux/kasan.h>
#include <trace/events/ipi.h>
static DEFINE_PER_CPU(struct llist_head, raised_list);
static DEFINE_PER_CPU(struct llist_head, lazy_list);
static DEFINE_PER_CPU(struct task_struct *, irq_workd);
static void wake_irq_workd(void)
{
struct task_struct *tsk = __this_cpu_read(irq_workd);
if (!llist_empty(this_cpu_ptr(&lazy_list)) && tsk)
wake_up_process(tsk);
}
#ifdef CONFIG_SMP
static void irq_work_wake(struct irq_work *entry)
{
wake_irq_workd();
}
static DEFINE_PER_CPU(struct irq_work, irq_work_wakeup) =
IRQ_WORK_INIT_HARD(irq_work_wake);
#endif
static int irq_workd_should_run(unsigned int cpu)
{
return !llist_empty(this_cpu_ptr(&lazy_list));
}
/*
* Claim the entry so that no one else will poke at it.
*/
static bool irq_work_claim(struct irq_work *work)
{
int oflags;
oflags = atomic_fetch_or(IRQ_WORK_CLAIMED | CSD_TYPE_IRQ_WORK, &work->node.a_flags);
/*
* If the work is already pending, no need to raise the IPI.
* The pairing smp_mb() in irq_work_single() makes sure
* everything we did before is visible.
*/
if (oflags & IRQ_WORK_PENDING)
return false;
return true;
}
void __weak arch_irq_work_raise(void)
{
/*
* Lame architectures will get the timer tick callback
*/
}
static __always_inline void irq_work_raise(struct irq_work *work)
{
if (trace_ipi_send_cpu_enabled() && arch_irq_work_has_interrupt())
trace_call__ipi_send_cpu(smp_processor_id(), _RET_IP_, work->func);
arch_irq_work_raise();
}
/* Enqueue on current CPU, work must already be claimed and preempt disabled */
static void __irq_work_queue_local(struct irq_work *work)
{
struct llist_head *list;
bool rt_lazy_work = false;
bool lazy_work = false;
int work_flags;
work_flags = atomic_read(&work->node.a_flags);
if (work_flags & IRQ_WORK_LAZY)
lazy_work = true;
else if (IS_ENABLED(CONFIG_PREEMPT_RT) &&
!(work_flags & IRQ_WORK_HARD_IRQ))
rt_lazy_work = true;
if (lazy_work || rt_lazy_work)
list = this_cpu_ptr(&lazy_list);
else
list = this_cpu_ptr(&raised_list);
if (!llist_add(&work->node.llist, list))
return;
/* If the work is "lazy", handle it from next tick if any */
if (!lazy_work || tick_nohz_tick_stopped())
irq_work_raise(work);
}
/* Enqueue the irq work @work on the current CPU */
bool irq_work_queue(struct irq_work *work)
{
/* Only queue if not already pending */
if (!irq_work_claim(work))
return false;
/* Queue the entry and raise the IPI if needed. */
preempt_disable();
__irq_work_queue_local(work);
preempt_enable();
return true;
}
EXPORT_SYMBOL_GPL(irq_work_queue);
/*
* Enqueue the irq_work @work on @cpu unless it's already pending
* somewhere.
*
* Can be re-enqueued while the callback is still in progress.
*/
bool irq_work_queue_on(struct irq_work *work, int cpu)
{
#ifndef CONFIG_SMP
return irq_work_queue(work);
#else /* CONFIG_SMP: */
/* All work should have been flushed before going offline */
WARN_ON_ONCE(cpu_is_offline(cpu));
/* Only queue if not already pending */
if (!irq_work_claim(work))
return false;
kasan_record_aux_stack(work);
preempt_disable();
if (cpu != smp_processor_id()) {
/* Arch remote IPI send/receive backend aren't NMI safe */
WARN_ON_ONCE(in_nmi());
/*
* On PREEMPT_RT the items which are not marked as
* IRQ_WORK_HARD_IRQ are added to the lazy list and a HARD work
* item is used on the remote CPU to wake the thread.
*/
if (IS_ENABLED(CONFIG_PREEMPT_RT) &&
!(atomic_read(&work->node.a_flags) & IRQ_WORK_HARD_IRQ)) {
if (!llist_add(&work->node.llist, &per_cpu(lazy_list, cpu)))
goto out;
work = &per_cpu(irq_work_wakeup, cpu);
if (!irq_work_claim(work))
goto out;
}
__smp_call_single_queue(cpu, &work->node.llist);
} else {
__irq_work_queue_local(work);
}
out:
preempt_enable();
return true;
#endif /* CONFIG_SMP */
}
bool irq_work_needs_cpu(void)
{
struct llist_head *raised, *lazy;
raised = this_cpu_ptr(&raised_list);
lazy = this_cpu_ptr(&lazy_list);
if (llist_empty(raised) || arch_irq_work_has_interrupt())
if (llist_empty(lazy))
return false;
/* All work should have been flushed before going offline */
WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
return true;
}
void irq_work_single(void *arg)
{
struct irq_work *work = arg;
int flags;
/*
* Clear the PENDING bit, after this point the @work can be re-used.
* The PENDING bit acts as a lock, and we own it, so we can clear it
* without atomic ops.
*/
flags = atomic_read(&work->node.a_flags);
flags &= ~IRQ_WORK_PENDING;
atomic_set(&work->node.a_flags, flags);
/*
* See irq_work_claim().
*/
smp_mb();
lockdep_irq_work_enter(flags);
work->func(work);
lockdep_irq_work_exit(flags);
/*
* Clear the BUSY bit, if set, and return to the free state if no-one
* else claimed it meanwhile.
*/
(void)atomic_cmpxchg(&work->node.a_flags, flags, flags & ~IRQ_WORK_BUSY);
if ((IS_ENABLED(CONFIG_PREEMPT_RT) && !irq_work_is_hard(work)) ||
!arch_irq_work_has_interrupt())
rcuwait_wake_up(&work->irqwait);
}
static void irq_work_run_list(struct llist_head *list)
{
struct irq_work *work, *tmp;
struct llist_node *llnode;
/*
* On PREEMPT_RT IRQ-work which is not marked as HARD will be processed
* in a per-CPU thread in preemptible context. Only the items which are
* marked as IRQ_WORK_HARD_IRQ will be processed in hardirq context.
*/
BUG_ON(!irqs_disabled() && !IS_ENABLED(CONFIG_PREEMPT_RT));
if (llist_empty(list))
return;
llnode = llist_del_all(list);
llist_for_each_entry_safe(work, tmp, llnode, node.llist)
irq_work_single(work);
}
/* CPU hotplug calls this through smpcfd_dying_cpu() */
void irq_work_run(void)
{
irq_work_run_list(this_cpu_ptr(&raised_list));
if (!IS_ENABLED(CONFIG_PREEMPT_RT))
irq_work_run_list(this_cpu_ptr(&lazy_list));
else
wake_irq_workd();
}
EXPORT_SYMBOL_GPL(irq_work_run);
void irq_work_run_cpu(unsigned int cpu)
{
if (WARN_ON_ONCE(!cpumask_test_cpu(cpu, cpu_dying_mask)))
return;
if (!IS_ENABLED(CONFIG_PREEMPT_RT))
return;
irq_work_run_list(per_cpu_ptr(&lazy_list, cpu));
}
void irq_work_tick(void)
{
struct llist_head *raised = this_cpu_ptr(&raised_list);
if (!llist_empty(raised) && !arch_irq_work_has_interrupt())
irq_work_run_list(raised);
if (!IS_ENABLED(CONFIG_PREEMPT_RT))
irq_work_run_list(this_cpu_ptr(&lazy_list));
else
wake_irq_workd();
}
/*
* Synchronize against the irq_work @entry, ensures the entry is not
* currently in use.
*/
void irq_work_sync(struct irq_work *work)
{
lockdep_assert_irqs_enabled();
might_sleep();
if ((IS_ENABLED(CONFIG_PREEMPT_RT) && !irq_work_is_hard(work)) ||
!arch_irq_work_has_interrupt()) {
rcuwait_wait_event(&work->irqwait, !irq_work_is_busy(work),
TASK_UNINTERRUPTIBLE);
/*
* Ensure irq_work_single() does not access @work
* after removing IRQ_WORK_BUSY. It is always
* accessed within a RCU-read section.
*/
synchronize_rcu();
return;
}
while (irq_work_is_busy(work))
cpu_relax();
}
EXPORT_SYMBOL_GPL(irq_work_sync);
static void run_irq_workd(unsigned int cpu)
{
guard(rcu)();
irq_work_run_list(this_cpu_ptr(&lazy_list));
}
static void irq_workd_setup(unsigned int cpu)
{
sched_set_fifo_low(current);
}
static struct smp_hotplug_thread irqwork_threads = {
.store = &irq_workd,
.setup = irq_workd_setup,
.thread_should_run = irq_workd_should_run,
.thread_fn = run_irq_workd,
.thread_comm = "irq_work/%u",
};
static __init int irq_work_init_threads(void)
{
if (IS_ENABLED(CONFIG_PREEMPT_RT))
BUG_ON(smpboot_register_percpu_thread(&irqwork_threads));
return 0;
}
early_initcall(irq_work_init_threads);