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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/bug.h>
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 <asm/processor.h>
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
24 */
25
26#define IRQ_WORK_PENDING 1UL
27#define IRQ_WORK_BUSY 2UL
28#define IRQ_WORK_FLAGS 3UL
29
30static DEFINE_PER_CPU(struct llist_head, irq_work_list);
31
32/*
33 * Claim the entry so that no one else will poke at it.
34 */
35static bool irq_work_claim(struct irq_work *work)
36{
37 unsigned long flags, nflags;
38
39 for (;;) {
40 flags = work->flags;
41 if (flags & IRQ_WORK_PENDING)
42 return false;
43 nflags = flags | IRQ_WORK_FLAGS;
44 if (cmpxchg(&work->flags, flags, nflags) == flags)
45 break;
46 cpu_relax();
47 }
48
49 return true;
50}
51
52void __weak arch_irq_work_raise(void)
53{
54 /*
55 * Lame architectures will get the timer tick callback
56 */
57}
58
59/*
60 * Queue the entry and raise the IPI if needed.
61 */
62static void __irq_work_queue(struct irq_work *work)
63{
64 bool empty;
65
66 preempt_disable();
67
68 empty = llist_add(&work->llnode, &__get_cpu_var(irq_work_list));
69 /* The list was empty, raise self-interrupt to start processing. */
70 if (empty)
71 arch_irq_work_raise();
72
73 preempt_enable();
74}
75
76/*
77 * Enqueue the irq_work @entry, returns true on success, failure when the
78 * @entry was already enqueued by someone else.
79 *
80 * Can be re-enqueued while the callback is still in progress.
81 */
82bool irq_work_queue(struct irq_work *work)
83{
84 if (!irq_work_claim(work)) {
85 /*
86 * Already enqueued, can't do!
87 */
88 return false;
89 }
90
91 __irq_work_queue(work);
92 return true;
93}
94EXPORT_SYMBOL_GPL(irq_work_queue);
95
96/*
97 * Run the irq_work entries on this cpu. Requires to be ran from hardirq
98 * context with local IRQs disabled.
99 */
100void irq_work_run(void)
101{
102 struct irq_work *work;
103 struct llist_head *this_list;
104 struct llist_node *llnode;
105
106 this_list = &__get_cpu_var(irq_work_list);
107 if (llist_empty(this_list))
108 return;
109
110 BUG_ON(!in_irq());
111 BUG_ON(!irqs_disabled());
112
113 llnode = llist_del_all(this_list);
114 while (llnode != NULL) {
115 work = llist_entry(llnode, struct irq_work, llnode);
116
117 llnode = llist_next(llnode);
118
119 /*
120 * Clear the PENDING bit, after this point the @work
121 * can be re-used.
122 */
123 work->flags = IRQ_WORK_BUSY;
124 work->func(work);
125 /*
126 * Clear the BUSY bit and return to the free state if
127 * no-one else claimed it meanwhile.
128 */
129 (void)cmpxchg(&work->flags, IRQ_WORK_BUSY, 0);
130 }
131}
132EXPORT_SYMBOL_GPL(irq_work_run);
133
134/*
135 * Synchronize against the irq_work @entry, ensures the entry is not
136 * currently in use.
137 */
138void irq_work_sync(struct irq_work *work)
139{
140 WARN_ON_ONCE(irqs_disabled());
141
142 while (work->flags & IRQ_WORK_BUSY)
143 cpu_relax();
144}
145EXPORT_SYMBOL_GPL(irq_work_sync);
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
20 *
21 * We use the lower two bits of the next pointer to keep PENDING and BUSY
22 * flags.
23 */
24
25#define IRQ_WORK_PENDING 1UL
26#define IRQ_WORK_BUSY 2UL
27#define IRQ_WORK_FLAGS 3UL
28
29static inline bool irq_work_is_set(struct irq_work *entry, int flags)
30{
31 return (unsigned long)entry->next & flags;
32}
33
34static inline struct irq_work *irq_work_next(struct irq_work *entry)
35{
36 unsigned long next = (unsigned long)entry->next;
37 next &= ~IRQ_WORK_FLAGS;
38 return (struct irq_work *)next;
39}
40
41static inline struct irq_work *next_flags(struct irq_work *entry, int flags)
42{
43 unsigned long next = (unsigned long)entry;
44 next |= flags;
45 return (struct irq_work *)next;
46}
47
48static DEFINE_PER_CPU(struct irq_work *, irq_work_list);
49
50/*
51 * Claim the entry so that no one else will poke at it.
52 */
53static bool irq_work_claim(struct irq_work *entry)
54{
55 struct irq_work *next, *nflags;
56
57 do {
58 next = entry->next;
59 if ((unsigned long)next & IRQ_WORK_PENDING)
60 return false;
61 nflags = next_flags(next, IRQ_WORK_FLAGS);
62 } while (cmpxchg(&entry->next, next, nflags) != next);
63
64 return true;
65}
66
67
68void __weak arch_irq_work_raise(void)
69{
70 /*
71 * Lame architectures will get the timer tick callback
72 */
73}
74
75/*
76 * Queue the entry and raise the IPI if needed.
77 */
78static void __irq_work_queue(struct irq_work *entry)
79{
80 struct irq_work *next;
81
82 preempt_disable();
83
84 do {
85 next = __this_cpu_read(irq_work_list);
86 /* Can assign non-atomic because we keep the flags set. */
87 entry->next = next_flags(next, IRQ_WORK_FLAGS);
88 } while (this_cpu_cmpxchg(irq_work_list, next, entry) != next);
89
90 /* The list was empty, raise self-interrupt to start processing. */
91 if (!irq_work_next(entry))
92 arch_irq_work_raise();
93
94 preempt_enable();
95}
96
97/*
98 * Enqueue the irq_work @entry, returns true on success, failure when the
99 * @entry was already enqueued by someone else.
100 *
101 * Can be re-enqueued while the callback is still in progress.
102 */
103bool irq_work_queue(struct irq_work *entry)
104{
105 if (!irq_work_claim(entry)) {
106 /*
107 * Already enqueued, can't do!
108 */
109 return false;
110 }
111
112 __irq_work_queue(entry);
113 return true;
114}
115EXPORT_SYMBOL_GPL(irq_work_queue);
116
117/*
118 * Run the irq_work entries on this cpu. Requires to be ran from hardirq
119 * context with local IRQs disabled.
120 */
121void irq_work_run(void)
122{
123 struct irq_work *list;
124
125 if (this_cpu_read(irq_work_list) == NULL)
126 return;
127
128 BUG_ON(!in_irq());
129 BUG_ON(!irqs_disabled());
130
131 list = this_cpu_xchg(irq_work_list, NULL);
132
133 while (list != NULL) {
134 struct irq_work *entry = list;
135
136 list = irq_work_next(list);
137
138 /*
139 * Clear the PENDING bit, after this point the @entry
140 * can be re-used.
141 */
142 entry->next = next_flags(NULL, IRQ_WORK_BUSY);
143 entry->func(entry);
144 /*
145 * Clear the BUSY bit and return to the free state if
146 * no-one else claimed it meanwhile.
147 */
148 (void)cmpxchg(&entry->next,
149 next_flags(NULL, IRQ_WORK_BUSY),
150 NULL);
151 }
152}
153EXPORT_SYMBOL_GPL(irq_work_run);
154
155/*
156 * Synchronize against the irq_work @entry, ensures the entry is not
157 * currently in use.
158 */
159void irq_work_sync(struct irq_work *entry)
160{
161 WARN_ON_ONCE(irqs_disabled());
162
163 while (irq_work_is_set(entry, IRQ_WORK_BUSY))
164 cpu_relax();
165}
166EXPORT_SYMBOL_GPL(irq_work_sync);