1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
|
/*
* Copyright (C) 2010 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
*
* Provides a framework for enqueueing and running callbacks from hardirq
* context. The enqueueing is NMI-safe.
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/irq_work.h>
#include <linux/hardirq.h>
/*
* An entry can be in one of four states:
*
* free NULL, 0 -> {claimed} : free to be used
* claimed NULL, 3 -> {pending} : claimed to be enqueued
* pending next, 3 -> {busy} : queued, pending callback
* busy NULL, 2 -> {free, claimed} : callback in progress, can be claimed
*
* We use the lower two bits of the next pointer to keep PENDING and BUSY
* flags.
*/
#define IRQ_WORK_PENDING 1UL
#define IRQ_WORK_BUSY 2UL
#define IRQ_WORK_FLAGS 3UL
static inline bool irq_work_is_set(struct irq_work *entry, int flags)
{
return (unsigned long)entry->next & flags;
}
static inline struct irq_work *irq_work_next(struct irq_work *entry)
{
unsigned long next = (unsigned long)entry->next;
next &= ~IRQ_WORK_FLAGS;
return (struct irq_work *)next;
}
static inline struct irq_work *next_flags(struct irq_work *entry, int flags)
{
unsigned long next = (unsigned long)entry;
next |= flags;
return (struct irq_work *)next;
}
static DEFINE_PER_CPU(struct irq_work *, irq_work_list);
/*
* Claim the entry so that no one else will poke at it.
*/
static bool irq_work_claim(struct irq_work *entry)
{
struct irq_work *next, *nflags;
do {
next = entry->next;
if ((unsigned long)next & IRQ_WORK_PENDING)
return false;
nflags = next_flags(next, IRQ_WORK_FLAGS);
} while (cmpxchg(&entry->next, next, nflags) != next);
return true;
}
void __weak arch_irq_work_raise(void)
{
/*
* Lame architectures will get the timer tick callback
*/
}
/*
* Queue the entry and raise the IPI if needed.
*/
static void __irq_work_queue(struct irq_work *entry)
{
struct irq_work **head, *next;
head = &get_cpu_var(irq_work_list);
do {
next = *head;
/* Can assign non-atomic because we keep the flags set. */
entry->next = next_flags(next, IRQ_WORK_FLAGS);
} while (cmpxchg(head, next, entry) != next);
/* The list was empty, raise self-interrupt to start processing. */
if (!irq_work_next(entry))
arch_irq_work_raise();
put_cpu_var(irq_work_list);
}
/*
* Enqueue the irq_work @entry, returns true on success, failure when the
* @entry was already enqueued by someone else.
*
* Can be re-enqueued while the callback is still in progress.
*/
bool irq_work_queue(struct irq_work *entry)
{
if (!irq_work_claim(entry)) {
/*
* Already enqueued, can't do!
*/
return false;
}
__irq_work_queue(entry);
return true;
}
EXPORT_SYMBOL_GPL(irq_work_queue);
/*
* Run the irq_work entries on this cpu. Requires to be ran from hardirq
* context with local IRQs disabled.
*/
void irq_work_run(void)
{
struct irq_work *list, **head;
head = &__get_cpu_var(irq_work_list);
if (*head == NULL)
return;
BUG_ON(!in_irq());
BUG_ON(!irqs_disabled());
list = xchg(head, NULL);
while (list != NULL) {
struct irq_work *entry = list;
list = irq_work_next(list);
/*
* Clear the PENDING bit, after this point the @entry
* can be re-used.
*/
entry->next = next_flags(NULL, IRQ_WORK_BUSY);
entry->func(entry);
/*
* Clear the BUSY bit and return to the free state if
* no-one else claimed it meanwhile.
*/
cmpxchg(&entry->next, next_flags(NULL, IRQ_WORK_BUSY), NULL);
}
}
EXPORT_SYMBOL_GPL(irq_work_run);
/*
* Synchronize against the irq_work @entry, ensures the entry is not
* currently in use.
*/
void irq_work_sync(struct irq_work *entry)
{
WARN_ON_ONCE(irqs_disabled());
while (irq_work_is_set(entry, IRQ_WORK_BUSY))
cpu_relax();
}
EXPORT_SYMBOL_GPL(irq_work_sync);
|
