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
|
/*
* AioContext wait support
*
* Copyright (C) 2018 Red Hat, Inc.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#ifndef QEMU_AIO_WAIT_H
#define QEMU_AIO_WAIT_H
#include "block/aio.h"
#include "qemu/main-loop.h"
/**
* AioWait:
*
* An object that facilitates synchronous waiting on a condition. A single
* global AioWait object (global_aio_wait) is used internally.
*
* The main loop can wait on an operation running in an IOThread as follows:
*
* AioContext *ctx = ...;
* MyWork work = { .done = false };
* schedule_my_work_in_iothread(ctx, &work);
* AIO_WAIT_WHILE(ctx, !work.done);
*
* The IOThread must call aio_wait_kick() to notify the main loop when
* work.done changes:
*
* static void do_work(...)
* {
* ...
* work.done = true;
* aio_wait_kick();
* }
*/
typedef struct {
/* Number of waiting AIO_WAIT_WHILE() callers. Accessed with atomic ops. */
unsigned num_waiters;
} AioWait;
extern AioWait global_aio_wait;
/**
* AIO_WAIT_WHILE:
* @ctx: the aio context, or NULL if multiple aio contexts (for which the
* caller does not hold a lock) are involved in the polling condition.
* @cond: wait while this conditional expression is true
*
* Wait while a condition is true. Use this to implement synchronous
* operations that require event loop activity.
*
* The caller must be sure that something calls aio_wait_kick() when the value
* of @cond might have changed.
*
* The caller's thread must be the IOThread that owns @ctx or the main loop
* thread (with @ctx acquired exactly once). This function cannot be used to
* wait on conditions between two IOThreads since that could lead to deadlock,
* go via the main loop instead.
*/
#define AIO_WAIT_WHILE(ctx, cond) ({ \
bool waited_ = false; \
AioWait *wait_ = &global_aio_wait; \
AioContext *ctx_ = (ctx); \
/* Increment wait_->num_waiters before evaluating cond. */ \
qatomic_inc(&wait_->num_waiters); \
if (ctx_ && in_aio_context_home_thread(ctx_)) { \
while ((cond)) { \
aio_poll(ctx_, true); \
waited_ = true; \
} \
} else { \
assert(qemu_get_current_aio_context() == \
qemu_get_aio_context()); \
while ((cond)) { \
if (ctx_) { \
aio_context_release(ctx_); \
} \
aio_poll(qemu_get_aio_context(), true); \
if (ctx_) { \
aio_context_acquire(ctx_); \
} \
waited_ = true; \
} \
} \
qatomic_dec(&wait_->num_waiters); \
waited_; })
/**
* aio_wait_kick:
* Wake up the main thread if it is waiting on AIO_WAIT_WHILE(). During
* synchronous operations performed in an IOThread, the main thread lets the
* IOThread's event loop run, waiting for the operation to complete. A
* aio_wait_kick() call will wake up the main thread.
*/
void aio_wait_kick(void);
/**
* aio_wait_bh_oneshot:
* @ctx: the aio context
* @cb: the BH callback function
* @opaque: user data for the BH callback function
*
* Run a BH in @ctx and wait for it to complete.
*
* Must be called from the main loop thread with @ctx acquired exactly once.
* Note that main loop event processing may occur.
*/
void aio_wait_bh_oneshot(AioContext *ctx, QEMUBHFunc *cb, void *opaque);
/**
* in_aio_context_home_thread:
* @ctx: the aio context
*
* Return whether we are running in the thread that normally runs @ctx. Note
* that acquiring/releasing ctx does not affect the outcome, each AioContext
* still only has one home thread that is responsible for running it.
*/
static inline bool in_aio_context_home_thread(AioContext *ctx)
{
if (ctx == qemu_get_current_aio_context()) {
return true;
}
if (ctx == qemu_get_aio_context()) {
return qemu_mutex_iothread_locked();
} else {
return false;
}
}
#endif /* QEMU_AIO_WAIT_H */
|
