2 * Copyright (C) 2010 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
4 * Provides a framework for enqueueing and running callbacks from hardirq
5 * context. The enqueueing is NMI-safe.
9 #include <linux/kernel.h>
10 #include <linux/export.h>
11 #include <linux/irq_work.h>
12 #include <linux/percpu.h>
13 #include <linux/hardirq.h>
14 #include <linux/irqflags.h>
15 #include <asm/processor.h>
18 * An entry can be in one of four states:
20 * free NULL, 0 -> {claimed} : free to be used
21 * claimed NULL, 3 -> {pending} : claimed to be enqueued
22 * pending next, 3 -> {busy} : queued, pending callback
23 * busy NULL, 2 -> {free, claimed} : callback in progress, can be claimed
26 #define IRQ_WORK_PENDING 1UL
27 #define IRQ_WORK_BUSY 2UL
28 #define IRQ_WORK_FLAGS 3UL
30 static DEFINE_PER_CPU(struct llist_head, irq_work_list);
33 * Claim the entry so that no one else will poke at it.
35 static bool irq_work_claim(struct irq_work *work)
37 unsigned long flags, nflags;
41 if (flags & IRQ_WORK_PENDING)
43 nflags = flags | IRQ_WORK_FLAGS;
44 if (cmpxchg(&work->flags, flags, nflags) == flags)
52 void __weak arch_irq_work_raise(void)
55 * Lame architectures will get the timer tick callback
60 * Queue the entry and raise the IPI if needed.
62 static void __irq_work_queue(struct irq_work *work)
68 empty = llist_add(&work->llnode, &__get_cpu_var(irq_work_list));
69 /* The list was empty, raise self-interrupt to start processing. */
71 arch_irq_work_raise();
77 * Enqueue the irq_work @entry, returns true on success, failure when the
78 * @entry was already enqueued by someone else.
80 * Can be re-enqueued while the callback is still in progress.
82 bool irq_work_queue(struct irq_work *work)
84 if (!irq_work_claim(work)) {
86 * Already enqueued, can't do!
91 __irq_work_queue(work);
94 EXPORT_SYMBOL_GPL(irq_work_queue);
97 * Run the irq_work entries on this cpu. Requires to be ran from hardirq
98 * context with local IRQs disabled.
100 void irq_work_run(void)
102 struct irq_work *work;
103 struct llist_head *this_list;
104 struct llist_node *llnode;
106 this_list = &__get_cpu_var(irq_work_list);
107 if (llist_empty(this_list))
111 BUG_ON(!irqs_disabled());
113 llnode = llist_del_all(this_list);
114 while (llnode != NULL) {
115 work = llist_entry(llnode, struct irq_work, llnode);
117 llnode = llist_next(llnode);
120 * Clear the PENDING bit, after this point the @work
122 * Make it immediately visible so that other CPUs trying
123 * to claim that work don't rely on us to handle their data
124 * while we are in the middle of the func.
126 xchg(&work->flags, IRQ_WORK_BUSY);
129 * Clear the BUSY bit and return to the free state if
130 * no-one else claimed it meanwhile.
132 (void)cmpxchg(&work->flags, IRQ_WORK_BUSY, 0);
135 EXPORT_SYMBOL_GPL(irq_work_run);
138 * Synchronize against the irq_work @entry, ensures the entry is not
141 void irq_work_sync(struct irq_work *work)
143 WARN_ON_ONCE(irqs_disabled());
145 while (work->flags & IRQ_WORK_BUSY)
148 EXPORT_SYMBOL_GPL(irq_work_sync);