block: replace unchecked strdup/malloc/calloc with glib
[qemu.git] / qemu-coroutine.h
1 /*
2 * QEMU coroutine implementation
3 *
4 * Copyright IBM, Corp. 2011
5 *
6 * Authors:
7 * Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
8 * Kevin Wolf <kwolf@redhat.com>
9 *
10 * This work is licensed under the terms of the GNU LGPL, version 2 or later.
11 * See the COPYING.LIB file in the top-level directory.
12 *
13 */
14
15 #ifndef QEMU_COROUTINE_H
16 #define QEMU_COROUTINE_H
17
18 #include <stdbool.h>
19 #include "qemu-queue.h"
20
21 /**
22 * Coroutines are a mechanism for stack switching and can be used for
23 * cooperative userspace threading. These functions provide a simple but
24 * useful flavor of coroutines that is suitable for writing sequential code,
25 * rather than callbacks, for operations that need to give up control while
26 * waiting for events to complete.
27 *
28 * These functions are re-entrant and may be used outside the global mutex.
29 */
30
31 /**
32 * Mark a function that executes in coroutine context
33 *
34 * Functions that execute in coroutine context cannot be called directly from
35 * normal functions. In the future it would be nice to enable compiler or
36 * static checker support for catching such errors. This annotation might make
37 * it possible and in the meantime it serves as documentation.
38 *
39 * For example:
40 *
41 * static void coroutine_fn foo(void) {
42 * ....
43 * }
44 */
45 #define coroutine_fn
46
47 typedef struct Coroutine Coroutine;
48
49 /**
50 * Coroutine entry point
51 *
52 * When the coroutine is entered for the first time, opaque is passed in as an
53 * argument.
54 *
55 * When this function returns, the coroutine is destroyed automatically and
56 * execution continues in the caller who last entered the coroutine.
57 */
58 typedef void coroutine_fn CoroutineEntry(void *opaque);
59
60 /**
61 * Create a new coroutine
62 *
63 * Use qemu_coroutine_enter() to actually transfer control to the coroutine.
64 */
65 Coroutine *qemu_coroutine_create(CoroutineEntry *entry);
66
67 /**
68 * Transfer control to a coroutine
69 *
70 * The opaque argument is passed as the argument to the entry point when
71 * entering the coroutine for the first time. It is subsequently ignored.
72 */
73 void qemu_coroutine_enter(Coroutine *coroutine, void *opaque);
74
75 /**
76 * Transfer control back to a coroutine's caller
77 *
78 * This function does not return until the coroutine is re-entered using
79 * qemu_coroutine_enter().
80 */
81 void coroutine_fn qemu_coroutine_yield(void);
82
83 /**
84 * Get the currently executing coroutine
85 */
86 Coroutine *coroutine_fn qemu_coroutine_self(void);
87
88 /**
89 * Return whether or not currently inside a coroutine
90 *
91 * This can be used to write functions that work both when in coroutine context
92 * and when not in coroutine context. Note that such functions cannot use the
93 * coroutine_fn annotation since they work outside coroutine context.
94 */
95 bool qemu_in_coroutine(void);
96
97
98
99 /**
100 * CoQueues are a mechanism to queue coroutines in order to continue executing
101 * them later. They provide the fundamental primitives on which coroutine locks
102 * are built.
103 */
104 typedef struct CoQueue {
105 QTAILQ_HEAD(, Coroutine) entries;
106 } CoQueue;
107
108 /**
109 * Initialise a CoQueue. This must be called before any other operation is used
110 * on the CoQueue.
111 */
112 void qemu_co_queue_init(CoQueue *queue);
113
114 /**
115 * Adds the current coroutine to the CoQueue and transfers control to the
116 * caller of the coroutine.
117 */
118 void coroutine_fn qemu_co_queue_wait(CoQueue *queue);
119
120 /**
121 * Adds the current coroutine to the head of the CoQueue and transfers control to the
122 * caller of the coroutine.
123 */
124 void coroutine_fn qemu_co_queue_wait_insert_head(CoQueue *queue);
125
126 /**
127 * Restarts the next coroutine in the CoQueue and removes it from the queue.
128 *
129 * Returns true if a coroutine was restarted, false if the queue is empty.
130 */
131 bool qemu_co_queue_next(CoQueue *queue);
132
133 /**
134 * Restarts all coroutines in the CoQueue and leaves the queue empty.
135 */
136 void qemu_co_queue_restart_all(CoQueue *queue);
137
138 /**
139 * Checks if the CoQueue is empty.
140 */
141 bool qemu_co_queue_empty(CoQueue *queue);
142
143
144 /**
145 * Provides a mutex that can be used to synchronise coroutines
146 */
147 typedef struct CoMutex {
148 bool locked;
149 CoQueue queue;
150 } CoMutex;
151
152 /**
153 * Initialises a CoMutex. This must be called before any other operation is used
154 * on the CoMutex.
155 */
156 void qemu_co_mutex_init(CoMutex *mutex);
157
158 /**
159 * Locks the mutex. If the lock cannot be taken immediately, control is
160 * transferred to the caller of the current coroutine.
161 */
162 void coroutine_fn qemu_co_mutex_lock(CoMutex *mutex);
163
164 /**
165 * Unlocks the mutex and schedules the next coroutine that was waiting for this
166 * lock to be run.
167 */
168 void coroutine_fn qemu_co_mutex_unlock(CoMutex *mutex);
169
170 typedef struct CoRwlock {
171 bool writer;
172 int reader;
173 CoQueue queue;
174 } CoRwlock;
175
176 /**
177 * Initialises a CoRwlock. This must be called before any other operation
178 * is used on the CoRwlock
179 */
180 void qemu_co_rwlock_init(CoRwlock *lock);
181
182 /**
183 * Read locks the CoRwlock. If the lock cannot be taken immediately because
184 * of a parallel writer, control is transferred to the caller of the current
185 * coroutine.
186 */
187 void qemu_co_rwlock_rdlock(CoRwlock *lock);
188
189 /**
190 * Write Locks the mutex. If the lock cannot be taken immediately because
191 * of a parallel reader, control is transferred to the caller of the current
192 * coroutine.
193 */
194 void qemu_co_rwlock_wrlock(CoRwlock *lock);
195
196 /**
197 * Unlocks the read/write lock and schedules the next coroutine that was
198 * waiting for this lock to be run.
199 */
200 void qemu_co_rwlock_unlock(CoRwlock *lock);
201
202 #endif /* QEMU_COROUTINE_H */