165 lines
3.7 KiB
C
165 lines
3.7 KiB
C
/*
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* Copyright (C) 2010 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
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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/kernel.h>
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#include <linux/module.h>
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#include <linux/irq_work.h>
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#include <linux/hardirq.h>
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/*
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* An entry can be in one of four states:
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*
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* free NULL, 0 -> {claimed} : free to be used
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* claimed NULL, 3 -> {pending} : claimed to be enqueued
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* pending next, 3 -> {busy} : queued, pending callback
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* busy NULL, 2 -> {free, claimed} : callback in progress, can be claimed
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*
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* We use the lower two bits of the next pointer to keep PENDING and BUSY
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* flags.
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*/
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#define IRQ_WORK_PENDING 1UL
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#define IRQ_WORK_BUSY 2UL
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#define IRQ_WORK_FLAGS 3UL
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static inline bool irq_work_is_set(struct irq_work *entry, int flags)
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{
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return (unsigned long)entry->next & flags;
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}
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static inline struct irq_work *irq_work_next(struct irq_work *entry)
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{
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unsigned long next = (unsigned long)entry->next;
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next &= ~IRQ_WORK_FLAGS;
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return (struct irq_work *)next;
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}
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static inline struct irq_work *next_flags(struct irq_work *entry, int flags)
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{
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unsigned long next = (unsigned long)entry;
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next |= flags;
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return (struct irq_work *)next;
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}
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static DEFINE_PER_CPU(struct irq_work *, irq_work_list);
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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 *entry)
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{
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struct irq_work *next, *nflags;
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do {
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next = entry->next;
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if ((unsigned long)next & IRQ_WORK_PENDING)
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return false;
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nflags = next_flags(next, IRQ_WORK_FLAGS);
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} while (cmpxchg(&entry->next, next, nflags) != next);
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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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/*
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* Queue the entry and raise the IPI if needed.
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*/
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static void __irq_work_queue(struct irq_work *entry)
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{
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struct irq_work **head, *next;
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head = &get_cpu_var(irq_work_list);
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do {
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next = *head;
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/* Can assign non-atomic because we keep the flags set. */
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entry->next = next_flags(next, IRQ_WORK_FLAGS);
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} while (cmpxchg(head, next, entry) != next);
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/* The list was empty, raise self-interrupt to start processing. */
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if (!irq_work_next(entry))
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arch_irq_work_raise();
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put_cpu_var(irq_work_list);
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}
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/*
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* Enqueue the irq_work @entry, returns true on success, failure when the
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* @entry was already enqueued by someone else.
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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(struct irq_work *entry)
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{
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if (!irq_work_claim(entry)) {
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/*
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* Already enqueued, can't do!
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*/
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return false;
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}
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__irq_work_queue(entry);
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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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* Run the irq_work entries on this cpu. Requires to be ran from hardirq
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* context with local IRQs disabled.
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*/
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void irq_work_run(void)
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{
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struct irq_work *list, **head;
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head = &__get_cpu_var(irq_work_list);
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if (*head == NULL)
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return;
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BUG_ON(!in_irq());
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BUG_ON(!irqs_disabled());
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list = xchg(head, NULL);
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while (list != NULL) {
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struct irq_work *entry = list;
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list = irq_work_next(list);
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/*
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* Clear the PENDING bit, after this point the @entry
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* can be re-used.
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*/
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entry->next = next_flags(NULL, IRQ_WORK_BUSY);
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entry->func(entry);
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/*
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* Clear the BUSY bit and return to the free state if
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* no-one else claimed it meanwhile.
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*/
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cmpxchg(&entry->next, next_flags(NULL, IRQ_WORK_BUSY), NULL);
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}
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}
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EXPORT_SYMBOL_GPL(irq_work_run);
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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 *entry)
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{
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WARN_ON_ONCE(irqs_disabled());
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while (irq_work_is_set(entry, IRQ_WORK_BUSY))
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cpu_relax();
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}
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EXPORT_SYMBOL_GPL(irq_work_sync);
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