Commit | Line | Data |
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e360adbe PZ |
1 | /* |
2 | * Copyright (C) 2010 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com> | |
3 | * | |
4 | * Provides a framework for enqueueing and running callbacks from hardirq | |
5 | * context. The enqueueing is NMI-safe. | |
6 | */ | |
7 | ||
83e3fa6f | 8 | #include <linux/bug.h> |
e360adbe | 9 | #include <linux/kernel.h> |
9984de1a | 10 | #include <linux/export.h> |
e360adbe | 11 | #include <linux/irq_work.h> |
967d1f90 | 12 | #include <linux/percpu.h> |
e360adbe | 13 | #include <linux/hardirq.h> |
ef1f0982 | 14 | #include <linux/irqflags.h> |
bc6679ae FW |
15 | #include <linux/sched.h> |
16 | #include <linux/tick.h> | |
c0e980a4 SR |
17 | #include <linux/cpu.h> |
18 | #include <linux/notifier.h> | |
967d1f90 | 19 | #include <asm/processor.h> |
e360adbe | 20 | |
e360adbe | 21 | |
38aaf809 | 22 | static DEFINE_PER_CPU(struct llist_head, irq_work_list); |
bc6679ae | 23 | static DEFINE_PER_CPU(int, irq_work_raised); |
e360adbe PZ |
24 | |
25 | /* | |
26 | * Claim the entry so that no one else will poke at it. | |
27 | */ | |
38aaf809 | 28 | static bool irq_work_claim(struct irq_work *work) |
e360adbe | 29 | { |
e0bbe2d8 | 30 | unsigned long flags, oflags, nflags; |
e360adbe | 31 | |
e0bbe2d8 FW |
32 | /* |
33 | * Start with our best wish as a premise but only trust any | |
34 | * flag value after cmpxchg() result. | |
35 | */ | |
36 | flags = work->flags & ~IRQ_WORK_PENDING; | |
38aaf809 | 37 | for (;;) { |
38aaf809 | 38 | nflags = flags | IRQ_WORK_FLAGS; |
e0bbe2d8 FW |
39 | oflags = cmpxchg(&work->flags, flags, nflags); |
40 | if (oflags == flags) | |
38aaf809 | 41 | break; |
e0bbe2d8 FW |
42 | if (oflags & IRQ_WORK_PENDING) |
43 | return false; | |
44 | flags = oflags; | |
38aaf809 HY |
45 | cpu_relax(); |
46 | } | |
e360adbe PZ |
47 | |
48 | return true; | |
49 | } | |
50 | ||
e360adbe PZ |
51 | void __weak arch_irq_work_raise(void) |
52 | { | |
53 | /* | |
54 | * Lame architectures will get the timer tick callback | |
55 | */ | |
56 | } | |
57 | ||
58 | /* | |
c02cf5f8 | 59 | * Enqueue the irq_work @entry unless it's already pending |
60 | * somewhere. | |
61 | * | |
62 | * Can be re-enqueued while the callback is still in progress. | |
e360adbe | 63 | */ |
c02cf5f8 | 64 | void irq_work_queue(struct irq_work *work) |
e360adbe | 65 | { |
c02cf5f8 | 66 | /* Only queue if not already pending */ |
67 | if (!irq_work_claim(work)) | |
68 | return; | |
69 | ||
70 | /* Queue the entry and raise the IPI if needed. */ | |
20b87691 | 71 | preempt_disable(); |
e360adbe | 72 | |
bc6679ae FW |
73 | llist_add(&work->llnode, &__get_cpu_var(irq_work_list)); |
74 | ||
75 | /* | |
76 | * If the work is not "lazy" or the tick is stopped, raise the irq | |
77 | * work interrupt (if supported by the arch), otherwise, just wait | |
78 | * for the next tick. | |
79 | */ | |
80 | if (!(work->flags & IRQ_WORK_LAZY) || tick_nohz_tick_stopped()) { | |
81 | if (!this_cpu_cmpxchg(irq_work_raised, 0, 1)) | |
82 | arch_irq_work_raise(); | |
83 | } | |
e360adbe | 84 | |
20b87691 | 85 | preempt_enable(); |
e360adbe | 86 | } |
e360adbe PZ |
87 | EXPORT_SYMBOL_GPL(irq_work_queue); |
88 | ||
00b42959 FW |
89 | bool irq_work_needs_cpu(void) |
90 | { | |
91 | struct llist_head *this_list; | |
92 | ||
93 | this_list = &__get_cpu_var(irq_work_list); | |
94 | if (llist_empty(this_list)) | |
95 | return false; | |
96 | ||
8aa2acce SR |
97 | /* All work should have been flushed before going offline */ |
98 | WARN_ON_ONCE(cpu_is_offline(smp_processor_id())); | |
99 | ||
00b42959 FW |
100 | return true; |
101 | } | |
102 | ||
c0e980a4 | 103 | static void __irq_work_run(void) |
e360adbe | 104 | { |
bc6679ae | 105 | unsigned long flags; |
38aaf809 HY |
106 | struct irq_work *work; |
107 | struct llist_head *this_list; | |
108 | struct llist_node *llnode; | |
e360adbe | 109 | |
bc6679ae FW |
110 | |
111 | /* | |
112 | * Reset the "raised" state right before we check the list because | |
113 | * an NMI may enqueue after we find the list empty from the runner. | |
114 | */ | |
115 | __this_cpu_write(irq_work_raised, 0); | |
116 | barrier(); | |
117 | ||
38aaf809 HY |
118 | this_list = &__get_cpu_var(irq_work_list); |
119 | if (llist_empty(this_list)) | |
e360adbe PZ |
120 | return; |
121 | ||
e360adbe PZ |
122 | BUG_ON(!irqs_disabled()); |
123 | ||
38aaf809 HY |
124 | llnode = llist_del_all(this_list); |
125 | while (llnode != NULL) { | |
126 | work = llist_entry(llnode, struct irq_work, llnode); | |
e360adbe | 127 | |
924f8f5a | 128 | llnode = llist_next(llnode); |
e360adbe PZ |
129 | |
130 | /* | |
38aaf809 | 131 | * Clear the PENDING bit, after this point the @work |
e360adbe | 132 | * can be re-used. |
c8446b75 FW |
133 | * Make it immediately visible so that other CPUs trying |
134 | * to claim that work don't rely on us to handle their data | |
135 | * while we are in the middle of the func. | |
e360adbe | 136 | */ |
bc6679ae FW |
137 | flags = work->flags & ~IRQ_WORK_PENDING; |
138 | xchg(&work->flags, flags); | |
139 | ||
38aaf809 | 140 | work->func(work); |
e360adbe PZ |
141 | /* |
142 | * Clear the BUSY bit and return to the free state if | |
143 | * no-one else claimed it meanwhile. | |
144 | */ | |
bc6679ae | 145 | (void)cmpxchg(&work->flags, flags, flags & ~IRQ_WORK_BUSY); |
e360adbe PZ |
146 | } |
147 | } | |
c0e980a4 SR |
148 | |
149 | /* | |
150 | * Run the irq_work entries on this cpu. Requires to be ran from hardirq | |
151 | * context with local IRQs disabled. | |
152 | */ | |
153 | void irq_work_run(void) | |
154 | { | |
155 | BUG_ON(!in_irq()); | |
156 | __irq_work_run(); | |
157 | } | |
e360adbe PZ |
158 | EXPORT_SYMBOL_GPL(irq_work_run); |
159 | ||
160 | /* | |
161 | * Synchronize against the irq_work @entry, ensures the entry is not | |
162 | * currently in use. | |
163 | */ | |
38aaf809 | 164 | void irq_work_sync(struct irq_work *work) |
e360adbe PZ |
165 | { |
166 | WARN_ON_ONCE(irqs_disabled()); | |
167 | ||
38aaf809 | 168 | while (work->flags & IRQ_WORK_BUSY) |
e360adbe PZ |
169 | cpu_relax(); |
170 | } | |
171 | EXPORT_SYMBOL_GPL(irq_work_sync); | |
c0e980a4 SR |
172 | |
173 | #ifdef CONFIG_HOTPLUG_CPU | |
174 | static int irq_work_cpu_notify(struct notifier_block *self, | |
175 | unsigned long action, void *hcpu) | |
176 | { | |
177 | long cpu = (long)hcpu; | |
178 | ||
179 | switch (action) { | |
180 | case CPU_DYING: | |
181 | /* Called from stop_machine */ | |
182 | if (WARN_ON_ONCE(cpu != smp_processor_id())) | |
183 | break; | |
184 | __irq_work_run(); | |
185 | break; | |
186 | default: | |
187 | break; | |
188 | } | |
189 | return NOTIFY_OK; | |
190 | } | |
191 | ||
192 | static struct notifier_block cpu_notify; | |
193 | ||
194 | static __init int irq_work_init_cpu_notifier(void) | |
195 | { | |
196 | cpu_notify.notifier_call = irq_work_cpu_notify; | |
197 | cpu_notify.priority = 0; | |
198 | register_cpu_notifier(&cpu_notify); | |
199 | return 0; | |
200 | } | |
201 | device_initcall(irq_work_init_cpu_notifier); | |
202 | ||
203 | #endif /* CONFIG_HOTPLUG_CPU */ |