2 * Copyright (C) 2010 Red Hat, Inc., Peter Zijlstra
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_CLAIMED;
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
60 * Enqueue the irq_work @work on @cpu unless it's already pending
63 * Can be re-enqueued while the callback is still in progress.
65 bool irq_work_queue_on(struct irq_work *work, int cpu)
67 /* All work should have been flushed before going offline */
68 WARN_ON_ONCE(cpu_is_offline(cpu));
72 /* Arch remote IPI send/receive backend aren't NMI safe */
73 WARN_ON_ONCE(in_nmi());
75 /* Only queue if not already pending */
76 if (!irq_work_claim(work))
79 if (llist_add(&work->llnode, &per_cpu(raised_list, cpu)))
80 arch_send_call_function_single_ipi(cpu);
82 #else /* #ifdef CONFIG_SMP */
84 #endif /* #else #ifdef CONFIG_SMP */
89 /* Enqueue the irq work @work on the current CPU */
90 bool irq_work_queue(struct irq_work *work)
92 /* Only queue if not already pending */
93 if (!irq_work_claim(work))
96 /* Queue the entry and raise the IPI if needed. */
99 /* If the work is "lazy", handle it from next tick if any */
100 if (work->flags & IRQ_WORK_LAZY) {
101 if (llist_add(&work->llnode, this_cpu_ptr(&lazy_list)) &&
102 tick_nohz_tick_stopped())
103 arch_irq_work_raise();
105 if (llist_add(&work->llnode, this_cpu_ptr(&raised_list)))
106 arch_irq_work_raise();
113 EXPORT_SYMBOL_GPL(irq_work_queue);
115 bool irq_work_needs_cpu(void)
117 struct llist_head *raised, *lazy;
119 raised = this_cpu_ptr(&raised_list);
120 lazy = this_cpu_ptr(&lazy_list);
122 if (llist_empty(raised) || arch_irq_work_has_interrupt())
123 if (llist_empty(lazy))
126 /* All work should have been flushed before going offline */
127 WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
132 static void irq_work_run_list(struct llist_head *list)
134 struct irq_work *work, *tmp;
135 struct llist_node *llnode;
138 BUG_ON(!irqs_disabled());
140 if (llist_empty(list))
143 llnode = llist_del_all(list);
144 llist_for_each_entry_safe(work, tmp, llnode, llnode) {
146 * Clear the PENDING bit, after this point the @work
148 * Make it immediately visible so that other CPUs trying
149 * to claim that work don't rely on us to handle their data
150 * while we are in the middle of the func.
152 flags = work->flags & ~IRQ_WORK_PENDING;
153 xchg(&work->flags, flags);
157 * Clear the BUSY bit and return to the free state if
158 * no-one else claimed it meanwhile.
160 (void)cmpxchg(&work->flags, flags, flags & ~IRQ_WORK_BUSY);
165 * hotplug calls this through:
166 * hotplug_cfd() -> flush_smp_call_function_queue()
168 void irq_work_run(void)
170 irq_work_run_list(this_cpu_ptr(&raised_list));
171 irq_work_run_list(this_cpu_ptr(&lazy_list));
173 EXPORT_SYMBOL_GPL(irq_work_run);
175 void irq_work_tick(void)
177 struct llist_head *raised = this_cpu_ptr(&raised_list);
179 if (!llist_empty(raised) && !arch_irq_work_has_interrupt())
180 irq_work_run_list(raised);
181 irq_work_run_list(this_cpu_ptr(&lazy_list));
185 * Synchronize against the irq_work @entry, ensures the entry is not
188 void irq_work_sync(struct irq_work *work)
190 lockdep_assert_irqs_enabled();
192 while (work->flags & IRQ_WORK_BUSY)
195 EXPORT_SYMBOL_GPL(irq_work_sync);