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 <linux/sched.h>
16 #include <linux/tick.h>
17 #include <linux/cpu.h>
18 #include <linux/notifier.h>
19 #include <linux/smp.h>
20 #include <asm/processor.h>
23 static DEFINE_PER_CPU(struct llist_head, raised_list);
24 static DEFINE_PER_CPU(struct llist_head, lazy_list);
27 * Claim the entry so that no one else will poke at it.
29 static bool irq_work_claim(struct irq_work *work)
31 unsigned long flags, oflags, nflags;
34 * Start with our best wish as a premise but only trust any
35 * flag value after cmpxchg() result.
37 flags = work->flags & ~IRQ_WORK_PENDING;
39 nflags = flags | IRQ_WORK_FLAGS;
40 oflags = cmpxchg(&work->flags, flags, nflags);
43 if (oflags & IRQ_WORK_PENDING)
52 void __weak arch_irq_work_raise(void)
55 * Lame architectures will get the timer tick callback
61 * Enqueue the irq_work @work on @cpu unless it's already pending
64 * Can be re-enqueued while the callback is still in progress.
66 bool irq_work_queue_on(struct irq_work *work, int cpu)
68 /* All work should have been flushed before going offline */
69 WARN_ON_ONCE(cpu_is_offline(cpu));
71 /* Arch remote IPI send/receive backend aren't NMI safe */
72 WARN_ON_ONCE(in_nmi());
74 /* Only queue if not already pending */
75 if (!irq_work_claim(work))
78 if (llist_add(&work->llnode, &per_cpu(raised_list, cpu)))
79 arch_send_call_function_single_ipi(cpu);
83 EXPORT_SYMBOL_GPL(irq_work_queue_on);
86 /* Enqueue the irq work @work on the current CPU */
87 bool irq_work_queue(struct irq_work *work)
89 /* Only queue if not already pending */
90 if (!irq_work_claim(work))
93 /* Queue the entry and raise the IPI if needed. */
96 /* If the work is "lazy", handle it from next tick if any */
97 if (work->flags & IRQ_WORK_LAZY) {
98 if (llist_add(&work->llnode, &__get_cpu_var(lazy_list)) &&
99 tick_nohz_tick_stopped())
100 arch_irq_work_raise();
102 if (llist_add(&work->llnode, &__get_cpu_var(raised_list)))
103 arch_irq_work_raise();
110 EXPORT_SYMBOL_GPL(irq_work_queue);
112 bool irq_work_needs_cpu(void)
114 struct llist_head *raised, *lazy;
116 raised = &__get_cpu_var(raised_list);
117 lazy = &__get_cpu_var(lazy_list);
118 if (llist_empty(raised) && llist_empty(lazy))
121 /* All work should have been flushed before going offline */
122 WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
127 static void irq_work_run_list(struct llist_head *list)
130 struct irq_work *work;
131 struct llist_node *llnode;
133 BUG_ON(!irqs_disabled());
135 if (llist_empty(list))
138 llnode = llist_del_all(list);
139 while (llnode != NULL) {
140 work = llist_entry(llnode, struct irq_work, llnode);
142 llnode = llist_next(llnode);
145 * Clear the PENDING bit, after this point the @work
147 * Make it immediately visible so that other CPUs trying
148 * to claim that work don't rely on us to handle their data
149 * while we are in the middle of the func.
151 flags = work->flags & ~IRQ_WORK_PENDING;
152 xchg(&work->flags, flags);
156 * Clear the BUSY bit and return to the free state if
157 * no-one else claimed it meanwhile.
159 (void)cmpxchg(&work->flags, flags, flags & ~IRQ_WORK_BUSY);
164 * hotplug calls this through:
165 * hotplug_cfd() -> flush_smp_call_function_queue()
167 void irq_work_run(void)
169 irq_work_run_list(&__get_cpu_var(raised_list));
170 irq_work_run_list(&__get_cpu_var(lazy_list));
172 EXPORT_SYMBOL_GPL(irq_work_run);
175 * Synchronize against the irq_work @entry, ensures the entry is not
178 void irq_work_sync(struct irq_work *work)
180 WARN_ON_ONCE(irqs_disabled());
182 while (work->flags & IRQ_WORK_BUSY)
185 EXPORT_SYMBOL_GPL(irq_work_sync);