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, oflags, nflags;
40 * Start with our best wish as a premise but only trust any
41 * flag value after cmpxchg() result.
43 flags = work->flags & ~IRQ_WORK_PENDING;
45 nflags = flags | IRQ_WORK_FLAGS;
46 oflags = cmpxchg(&work->flags, flags, nflags);
49 if (oflags & IRQ_WORK_PENDING)
58 void __weak arch_irq_work_raise(void)
61 * Lame architectures will get the timer tick callback
66 * Queue the entry and raise the IPI if needed.
68 static void __irq_work_queue(struct irq_work *work)
74 empty = llist_add(&work->llnode, &__get_cpu_var(irq_work_list));
75 /* The list was empty, raise self-interrupt to start processing. */
77 arch_irq_work_raise();
83 * Enqueue the irq_work @entry, returns true on success, failure when the
84 * @entry was already enqueued by someone else.
86 * Can be re-enqueued while the callback is still in progress.
88 bool irq_work_queue(struct irq_work *work)
90 if (!irq_work_claim(work)) {
92 * Already enqueued, can't do!
97 __irq_work_queue(work);
100 EXPORT_SYMBOL_GPL(irq_work_queue);
103 * Run the irq_work entries on this cpu. Requires to be ran from hardirq
104 * context with local IRQs disabled.
106 void irq_work_run(void)
108 struct irq_work *work;
109 struct llist_head *this_list;
110 struct llist_node *llnode;
112 this_list = &__get_cpu_var(irq_work_list);
113 if (llist_empty(this_list))
117 BUG_ON(!irqs_disabled());
119 llnode = llist_del_all(this_list);
120 while (llnode != NULL) {
121 work = llist_entry(llnode, struct irq_work, llnode);
123 llnode = llist_next(llnode);
126 * Clear the PENDING bit, after this point the @work
128 * Make it immediately visible so that other CPUs trying
129 * to claim that work don't rely on us to handle their data
130 * while we are in the middle of the func.
132 xchg(&work->flags, IRQ_WORK_BUSY);
135 * Clear the BUSY bit and return to the free state if
136 * no-one else claimed it meanwhile.
138 (void)cmpxchg(&work->flags, IRQ_WORK_BUSY, 0);
141 EXPORT_SYMBOL_GPL(irq_work_run);
144 * Synchronize against the irq_work @entry, ensures the entry is not
147 void irq_work_sync(struct irq_work *work)
149 WARN_ON_ONCE(irqs_disabled());
151 while (work->flags & IRQ_WORK_BUSY)
154 EXPORT_SYMBOL_GPL(irq_work_sync);