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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> |
c0e980a4 SR |
15 | #include <linux/cpu.h> |
16 | #include <linux/notifier.h> | |
967d1f90 | 17 | #include <asm/processor.h> |
e360adbe PZ |
18 | |
19 | /* | |
20 | * An entry can be in one of four states: | |
21 | * | |
22 | * free NULL, 0 -> {claimed} : free to be used | |
23 | * claimed NULL, 3 -> {pending} : claimed to be enqueued | |
24 | * pending next, 3 -> {busy} : queued, pending callback | |
25 | * busy NULL, 2 -> {free, claimed} : callback in progress, can be claimed | |
e360adbe PZ |
26 | */ |
27 | ||
28 | #define IRQ_WORK_PENDING 1UL | |
29 | #define IRQ_WORK_BUSY 2UL | |
30 | #define IRQ_WORK_FLAGS 3UL | |
31 | ||
38aaf809 | 32 | static DEFINE_PER_CPU(struct llist_head, irq_work_list); |
e360adbe PZ |
33 | |
34 | /* | |
35 | * Claim the entry so that no one else will poke at it. | |
36 | */ | |
38aaf809 | 37 | static bool irq_work_claim(struct irq_work *work) |
e360adbe | 38 | { |
e0bbe2d8 | 39 | unsigned long flags, oflags, nflags; |
e360adbe | 40 | |
e0bbe2d8 FW |
41 | /* |
42 | * Start with our best wish as a premise but only trust any | |
43 | * flag value after cmpxchg() result. | |
44 | */ | |
45 | flags = work->flags & ~IRQ_WORK_PENDING; | |
38aaf809 | 46 | for (;;) { |
38aaf809 | 47 | nflags = flags | IRQ_WORK_FLAGS; |
e0bbe2d8 FW |
48 | oflags = cmpxchg(&work->flags, flags, nflags); |
49 | if (oflags == flags) | |
38aaf809 | 50 | break; |
e0bbe2d8 FW |
51 | if (oflags & IRQ_WORK_PENDING) |
52 | return false; | |
53 | flags = oflags; | |
38aaf809 HY |
54 | cpu_relax(); |
55 | } | |
e360adbe PZ |
56 | |
57 | return true; | |
58 | } | |
59 | ||
e360adbe PZ |
60 | void __weak arch_irq_work_raise(void) |
61 | { | |
62 | /* | |
63 | * Lame architectures will get the timer tick callback | |
64 | */ | |
65 | } | |
66 | ||
67 | /* | |
68 | * Queue the entry and raise the IPI if needed. | |
69 | */ | |
38aaf809 | 70 | static void __irq_work_queue(struct irq_work *work) |
e360adbe | 71 | { |
38aaf809 | 72 | bool empty; |
e360adbe | 73 | |
20b87691 | 74 | preempt_disable(); |
e360adbe | 75 | |
38aaf809 | 76 | empty = llist_add(&work->llnode, &__get_cpu_var(irq_work_list)); |
e360adbe | 77 | /* The list was empty, raise self-interrupt to start processing. */ |
38aaf809 | 78 | if (empty) |
e360adbe PZ |
79 | arch_irq_work_raise(); |
80 | ||
20b87691 | 81 | preempt_enable(); |
e360adbe PZ |
82 | } |
83 | ||
84 | /* | |
85 | * Enqueue the irq_work @entry, returns true on success, failure when the | |
86 | * @entry was already enqueued by someone else. | |
87 | * | |
88 | * Can be re-enqueued while the callback is still in progress. | |
89 | */ | |
38aaf809 | 90 | bool irq_work_queue(struct irq_work *work) |
e360adbe | 91 | { |
38aaf809 | 92 | if (!irq_work_claim(work)) { |
e360adbe PZ |
93 | /* |
94 | * Already enqueued, can't do! | |
95 | */ | |
96 | return false; | |
97 | } | |
98 | ||
38aaf809 | 99 | __irq_work_queue(work); |
e360adbe PZ |
100 | return true; |
101 | } | |
102 | EXPORT_SYMBOL_GPL(irq_work_queue); | |
103 | ||
00b42959 FW |
104 | bool irq_work_needs_cpu(void) |
105 | { | |
106 | struct llist_head *this_list; | |
107 | ||
108 | this_list = &__get_cpu_var(irq_work_list); | |
109 | if (llist_empty(this_list)) | |
110 | return false; | |
111 | ||
112 | return true; | |
113 | } | |
114 | ||
c0e980a4 | 115 | static void __irq_work_run(void) |
e360adbe | 116 | { |
38aaf809 HY |
117 | struct irq_work *work; |
118 | struct llist_head *this_list; | |
119 | struct llist_node *llnode; | |
e360adbe | 120 | |
38aaf809 HY |
121 | this_list = &__get_cpu_var(irq_work_list); |
122 | if (llist_empty(this_list)) | |
e360adbe PZ |
123 | return; |
124 | ||
e360adbe PZ |
125 | BUG_ON(!irqs_disabled()); |
126 | ||
38aaf809 HY |
127 | llnode = llist_del_all(this_list); |
128 | while (llnode != NULL) { | |
129 | work = llist_entry(llnode, struct irq_work, llnode); | |
e360adbe | 130 | |
924f8f5a | 131 | llnode = llist_next(llnode); |
e360adbe PZ |
132 | |
133 | /* | |
38aaf809 | 134 | * Clear the PENDING bit, after this point the @work |
e360adbe | 135 | * can be re-used. |
c8446b75 FW |
136 | * Make it immediately visible so that other CPUs trying |
137 | * to claim that work don't rely on us to handle their data | |
138 | * while we are in the middle of the func. | |
e360adbe | 139 | */ |
c8446b75 | 140 | xchg(&work->flags, IRQ_WORK_BUSY); |
38aaf809 | 141 | work->func(work); |
e360adbe PZ |
142 | /* |
143 | * Clear the BUSY bit and return to the free state if | |
144 | * no-one else claimed it meanwhile. | |
145 | */ | |
38aaf809 | 146 | (void)cmpxchg(&work->flags, IRQ_WORK_BUSY, 0); |
e360adbe PZ |
147 | } |
148 | } | |
c0e980a4 SR |
149 | |
150 | /* | |
151 | * Run the irq_work entries on this cpu. Requires to be ran from hardirq | |
152 | * context with local IRQs disabled. | |
153 | */ | |
154 | void irq_work_run(void) | |
155 | { | |
156 | BUG_ON(!in_irq()); | |
157 | __irq_work_run(); | |
158 | } | |
e360adbe PZ |
159 | EXPORT_SYMBOL_GPL(irq_work_run); |
160 | ||
161 | /* | |
162 | * Synchronize against the irq_work @entry, ensures the entry is not | |
163 | * currently in use. | |
164 | */ | |
38aaf809 | 165 | void irq_work_sync(struct irq_work *work) |
e360adbe PZ |
166 | { |
167 | WARN_ON_ONCE(irqs_disabled()); | |
168 | ||
38aaf809 | 169 | while (work->flags & IRQ_WORK_BUSY) |
e360adbe PZ |
170 | cpu_relax(); |
171 | } | |
172 | EXPORT_SYMBOL_GPL(irq_work_sync); | |
c0e980a4 SR |
173 | |
174 | #ifdef CONFIG_HOTPLUG_CPU | |
175 | static int irq_work_cpu_notify(struct notifier_block *self, | |
176 | unsigned long action, void *hcpu) | |
177 | { | |
178 | long cpu = (long)hcpu; | |
179 | ||
180 | switch (action) { | |
181 | case CPU_DYING: | |
182 | /* Called from stop_machine */ | |
183 | if (WARN_ON_ONCE(cpu != smp_processor_id())) | |
184 | break; | |
185 | __irq_work_run(); | |
186 | break; | |
187 | default: | |
188 | break; | |
189 | } | |
190 | return NOTIFY_OK; | |
191 | } | |
192 | ||
193 | static struct notifier_block cpu_notify; | |
194 | ||
195 | static __init int irq_work_init_cpu_notifier(void) | |
196 | { | |
197 | cpu_notify.notifier_call = irq_work_cpu_notify; | |
198 | cpu_notify.priority = 0; | |
199 | register_cpu_notifier(&cpu_notify); | |
200 | return 0; | |
201 | } | |
202 | device_initcall(irq_work_init_cpu_notifier); | |
203 | ||
204 | #endif /* CONFIG_HOTPLUG_CPU */ |