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