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 | ||
8 | #include <linux/kernel.h> | |
9 | #include <linux/module.h> | |
10 | #include <linux/irq_work.h> | |
11 | #include <linux/hardirq.h> | |
12 | ||
13 | /* | |
14 | * An entry can be in one of four states: | |
15 | * | |
16 | * free NULL, 0 -> {claimed} : free to be used | |
17 | * claimed NULL, 3 -> {pending} : claimed to be enqueued | |
18 | * pending next, 3 -> {busy} : queued, pending callback | |
19 | * busy NULL, 2 -> {free, claimed} : callback in progress, can be claimed | |
e360adbe PZ |
20 | */ |
21 | ||
22 | #define IRQ_WORK_PENDING 1UL | |
23 | #define IRQ_WORK_BUSY 2UL | |
24 | #define IRQ_WORK_FLAGS 3UL | |
25 | ||
38aaf809 | 26 | static DEFINE_PER_CPU(struct llist_head, irq_work_list); |
e360adbe PZ |
27 | |
28 | /* | |
29 | * Claim the entry so that no one else will poke at it. | |
30 | */ | |
38aaf809 | 31 | static bool irq_work_claim(struct irq_work *work) |
e360adbe | 32 | { |
38aaf809 | 33 | unsigned long flags, nflags; |
e360adbe | 34 | |
38aaf809 HY |
35 | for (;;) { |
36 | flags = work->flags; | |
37 | if (flags & IRQ_WORK_PENDING) | |
e360adbe | 38 | return false; |
38aaf809 HY |
39 | nflags = flags | IRQ_WORK_FLAGS; |
40 | if (cmpxchg(&work->flags, flags, nflags) == flags) | |
41 | break; | |
42 | cpu_relax(); | |
43 | } | |
e360adbe PZ |
44 | |
45 | return true; | |
46 | } | |
47 | ||
e360adbe PZ |
48 | void __weak arch_irq_work_raise(void) |
49 | { | |
50 | /* | |
51 | * Lame architectures will get the timer tick callback | |
52 | */ | |
53 | } | |
54 | ||
55 | /* | |
56 | * Queue the entry and raise the IPI if needed. | |
57 | */ | |
38aaf809 | 58 | static void __irq_work_queue(struct irq_work *work) |
e360adbe | 59 | { |
38aaf809 | 60 | bool empty; |
e360adbe | 61 | |
20b87691 | 62 | preempt_disable(); |
e360adbe | 63 | |
38aaf809 | 64 | empty = llist_add(&work->llnode, &__get_cpu_var(irq_work_list)); |
e360adbe | 65 | /* The list was empty, raise self-interrupt to start processing. */ |
38aaf809 | 66 | if (empty) |
e360adbe PZ |
67 | arch_irq_work_raise(); |
68 | ||
20b87691 | 69 | preempt_enable(); |
e360adbe PZ |
70 | } |
71 | ||
72 | /* | |
73 | * Enqueue the irq_work @entry, returns true on success, failure when the | |
74 | * @entry was already enqueued by someone else. | |
75 | * | |
76 | * Can be re-enqueued while the callback is still in progress. | |
77 | */ | |
38aaf809 | 78 | bool irq_work_queue(struct irq_work *work) |
e360adbe | 79 | { |
38aaf809 | 80 | if (!irq_work_claim(work)) { |
e360adbe PZ |
81 | /* |
82 | * Already enqueued, can't do! | |
83 | */ | |
84 | return false; | |
85 | } | |
86 | ||
38aaf809 | 87 | __irq_work_queue(work); |
e360adbe PZ |
88 | return true; |
89 | } | |
90 | EXPORT_SYMBOL_GPL(irq_work_queue); | |
91 | ||
92 | /* | |
93 | * Run the irq_work entries on this cpu. Requires to be ran from hardirq | |
94 | * context with local IRQs disabled. | |
95 | */ | |
96 | void irq_work_run(void) | |
97 | { | |
38aaf809 HY |
98 | struct irq_work *work; |
99 | struct llist_head *this_list; | |
100 | struct llist_node *llnode; | |
e360adbe | 101 | |
38aaf809 HY |
102 | this_list = &__get_cpu_var(irq_work_list); |
103 | if (llist_empty(this_list)) | |
e360adbe PZ |
104 | return; |
105 | ||
106 | BUG_ON(!in_irq()); | |
107 | BUG_ON(!irqs_disabled()); | |
108 | ||
38aaf809 HY |
109 | llnode = llist_del_all(this_list); |
110 | while (llnode != NULL) { | |
111 | work = llist_entry(llnode, struct irq_work, llnode); | |
e360adbe | 112 | |
924f8f5a | 113 | llnode = llist_next(llnode); |
e360adbe PZ |
114 | |
115 | /* | |
38aaf809 | 116 | * Clear the PENDING bit, after this point the @work |
e360adbe PZ |
117 | * can be re-used. |
118 | */ | |
38aaf809 HY |
119 | work->flags = IRQ_WORK_BUSY; |
120 | work->func(work); | |
e360adbe PZ |
121 | /* |
122 | * Clear the BUSY bit and return to the free state if | |
123 | * no-one else claimed it meanwhile. | |
124 | */ | |
38aaf809 | 125 | (void)cmpxchg(&work->flags, IRQ_WORK_BUSY, 0); |
e360adbe PZ |
126 | } |
127 | } | |
128 | EXPORT_SYMBOL_GPL(irq_work_run); | |
129 | ||
130 | /* | |
131 | * Synchronize against the irq_work @entry, ensures the entry is not | |
132 | * currently in use. | |
133 | */ | |
38aaf809 | 134 | void irq_work_sync(struct irq_work *work) |
e360adbe PZ |
135 | { |
136 | WARN_ON_ONCE(irqs_disabled()); | |
137 | ||
38aaf809 | 138 | while (work->flags & IRQ_WORK_BUSY) |
e360adbe PZ |
139 | cpu_relax(); |
140 | } | |
141 | EXPORT_SYMBOL_GPL(irq_work_sync); |