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