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git.proxmox.com Git - mirror_ubuntu-bionic-kernel.git/blob - kernel/irq_work.c
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_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
59 /* Enqueue on current CPU, work must already be claimed and preempt disabled */
60 static void __irq_work_queue_local(struct irq_work
*work
)
62 /* If the work is "lazy", handle it from next tick if any */
63 if (work
->flags
& IRQ_WORK_LAZY
) {
64 if (llist_add(&work
->llnode
, this_cpu_ptr(&lazy_list
)) &&
65 tick_nohz_tick_stopped())
66 arch_irq_work_raise();
68 if (llist_add(&work
->llnode
, this_cpu_ptr(&raised_list
)))
69 arch_irq_work_raise();
73 /* Enqueue the irq work @work on the current CPU */
74 bool irq_work_queue(struct irq_work
*work
)
76 /* Only queue if not already pending */
77 if (!irq_work_claim(work
))
80 /* Queue the entry and raise the IPI if needed. */
82 __irq_work_queue_local(work
);
87 EXPORT_SYMBOL_GPL(irq_work_queue
);
90 * Enqueue the irq_work @work on @cpu unless it's already pending
93 * Can be re-enqueued while the callback is still in progress.
95 bool irq_work_queue_on(struct irq_work
*work
, int cpu
)
98 return irq_work_queue(work
);
100 #else /* CONFIG_SMP: */
101 /* All work should have been flushed before going offline */
102 WARN_ON_ONCE(cpu_is_offline(cpu
));
104 /* Only queue if not already pending */
105 if (!irq_work_claim(work
))
109 if (cpu
!= smp_processor_id()) {
110 /* Arch remote IPI send/receive backend aren't NMI safe */
111 WARN_ON_ONCE(in_nmi());
112 if (llist_add(&work
->llnode
, &per_cpu(raised_list
, cpu
)))
113 arch_send_call_function_single_ipi(cpu
);
115 __irq_work_queue_local(work
);
120 #endif /* CONFIG_SMP */
124 bool irq_work_needs_cpu(void)
126 struct llist_head
*raised
, *lazy
;
128 raised
= this_cpu_ptr(&raised_list
);
129 lazy
= this_cpu_ptr(&lazy_list
);
131 if (llist_empty(raised
) || arch_irq_work_has_interrupt())
132 if (llist_empty(lazy
))
135 /* All work should have been flushed before going offline */
136 WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
141 static void irq_work_run_list(struct llist_head
*list
)
143 struct irq_work
*work
, *tmp
;
144 struct llist_node
*llnode
;
147 BUG_ON(!irqs_disabled());
149 if (llist_empty(list
))
152 llnode
= llist_del_all(list
);
153 llist_for_each_entry_safe(work
, tmp
, llnode
, llnode
) {
155 * Clear the PENDING bit, after this point the @work
157 * Make it immediately visible so that other CPUs trying
158 * to claim that work don't rely on us to handle their data
159 * while we are in the middle of the func.
161 flags
= work
->flags
& ~IRQ_WORK_PENDING
;
162 xchg(&work
->flags
, flags
);
166 * Clear the BUSY bit and return to the free state if
167 * no-one else claimed it meanwhile.
169 (void)cmpxchg(&work
->flags
, flags
, flags
& ~IRQ_WORK_BUSY
);
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 (work
->flags
& IRQ_WORK_BUSY
)
204 EXPORT_SYMBOL_GPL(irq_work_sync
);