1 // SPDX-License-Identifier: GPL-2.0-only
3 * Copyright (C) 2010 Red Hat, Inc., Peter Zijlstra
5 * Provides a framework for enqueueing and running callbacks from hardirq
6 * context. The enqueueing is NMI-safe.
10 #include <linux/kernel.h>
11 #include <linux/export.h>
12 #include <linux/irq_work.h>
13 #include <linux/percpu.h>
14 #include <linux/hardirq.h>
15 #include <linux/irqflags.h>
16 #include <linux/sched.h>
17 #include <linux/tick.h>
18 #include <linux/cpu.h>
19 #include <linux/notifier.h>
20 #include <linux/smp.h>
21 #include <asm/processor.h>
24 static DEFINE_PER_CPU(struct llist_head, raised_list);
25 static DEFINE_PER_CPU(struct llist_head, lazy_list);
28 * Claim the entry so that no one else will poke at it.
30 static bool irq_work_claim(struct irq_work *work)
34 oflags = atomic_fetch_or(IRQ_WORK_CLAIMED | CSD_TYPE_IRQ_WORK, &work->flags);
36 * If the work is already pending, no need to raise the IPI.
37 * The pairing atomic_fetch_andnot() in irq_work_run() makes sure
38 * everything we did before is visible.
40 if (oflags & IRQ_WORK_PENDING)
45 void __weak arch_irq_work_raise(void)
48 * Lame architectures will get the timer tick callback
52 /* Enqueue on current CPU, work must already be claimed and preempt disabled */
53 static void __irq_work_queue_local(struct irq_work *work)
55 /* If the work is "lazy", handle it from next tick if any */
56 if (atomic_read(&work->flags) & IRQ_WORK_LAZY) {
57 if (llist_add(&work->llnode, this_cpu_ptr(&lazy_list)) &&
58 tick_nohz_tick_stopped())
59 arch_irq_work_raise();
61 if (llist_add(&work->llnode, this_cpu_ptr(&raised_list)))
62 arch_irq_work_raise();
66 /* Enqueue the irq work @work on the current CPU */
67 bool irq_work_queue(struct irq_work *work)
69 /* Only queue if not already pending */
70 if (!irq_work_claim(work))
73 /* Queue the entry and raise the IPI if needed. */
75 __irq_work_queue_local(work);
80 EXPORT_SYMBOL_GPL(irq_work_queue);
83 * Enqueue the irq_work @work on @cpu unless it's already pending
86 * Can be re-enqueued while the callback is still in progress.
88 bool irq_work_queue_on(struct irq_work *work, int cpu)
91 return irq_work_queue(work);
93 #else /* CONFIG_SMP: */
94 /* All work should have been flushed before going offline */
95 WARN_ON_ONCE(cpu_is_offline(cpu));
97 /* Only queue if not already pending */
98 if (!irq_work_claim(work))
102 if (cpu != smp_processor_id()) {
103 /* Arch remote IPI send/receive backend aren't NMI safe */
104 WARN_ON_ONCE(in_nmi());
105 __smp_call_single_queue(cpu, &work->llnode);
107 __irq_work_queue_local(work);
112 #endif /* CONFIG_SMP */
116 bool irq_work_needs_cpu(void)
118 struct llist_head *raised, *lazy;
120 raised = this_cpu_ptr(&raised_list);
121 lazy = this_cpu_ptr(&lazy_list);
123 if (llist_empty(raised) || arch_irq_work_has_interrupt())
124 if (llist_empty(lazy))
127 /* All work should have been flushed before going offline */
128 WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
133 void irq_work_single(void *arg)
135 struct irq_work *work = arg;
139 * Clear the PENDING bit, after this point the @work
141 * Make it immediately visible so that other CPUs trying
142 * to claim that work don't rely on us to handle their data
143 * while we are in the middle of the func.
145 flags = atomic_fetch_andnot(IRQ_WORK_PENDING, &work->flags);
147 lockdep_irq_work_enter(work);
149 lockdep_irq_work_exit(work);
151 * Clear the BUSY bit and return to the free state if
152 * no-one else claimed it meanwhile.
154 flags &= ~IRQ_WORK_PENDING;
155 (void)atomic_cmpxchg(&work->flags, flags, flags & ~IRQ_WORK_BUSY);
158 static void irq_work_run_list(struct llist_head *list)
160 struct irq_work *work, *tmp;
161 struct llist_node *llnode;
163 BUG_ON(!irqs_disabled());
165 if (llist_empty(list))
168 llnode = llist_del_all(list);
169 llist_for_each_entry_safe(work, tmp, llnode, llnode)
170 irq_work_single(work);
174 * hotplug calls this through:
175 * hotplug_cfd() -> flush_smp_call_function_queue()
177 void irq_work_run(void)
179 irq_work_run_list(this_cpu_ptr(&raised_list));
180 irq_work_run_list(this_cpu_ptr(&lazy_list));
182 EXPORT_SYMBOL_GPL(irq_work_run);
184 void irq_work_tick(void)
186 struct llist_head *raised = this_cpu_ptr(&raised_list);
188 if (!llist_empty(raised) && !arch_irq_work_has_interrupt())
189 irq_work_run_list(raised);
190 irq_work_run_list(this_cpu_ptr(&lazy_list));
194 * Synchronize against the irq_work @entry, ensures the entry is not
197 void irq_work_sync(struct irq_work *work)
199 lockdep_assert_irqs_enabled();
201 while (atomic_read(&work->flags) & IRQ_WORK_BUSY)
204 EXPORT_SYMBOL_GPL(irq_work_sync);