1 | /* |
2 | * QEMU System Emulator |
3 | * |
4 | * Copyright (c) 2003-2008 Fabrice Bellard |
5 | * |
6 | * Permission is hereby granted, free of charge, to any person obtaining a copy |
7 | * of this software and associated documentation files (the "Software"), to deal |
8 | * in the Software without restriction, including without limitation the rights |
9 | * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell |
10 | * copies of the Software, and to permit persons to whom the Software is |
11 | * furnished to do so, subject to the following conditions: |
12 | * |
13 | * The above copyright notice and this permission notice shall be included in |
14 | * all copies or substantial portions of the Software. |
15 | * |
16 | * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
17 | * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
18 | * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL |
19 | * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
20 | * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, |
21 | * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN |
22 | * THE SOFTWARE. |
23 | */ |
24 | |
25 | #ifndef QEMU_MAIN_LOOP_H |
26 | #define QEMU_MAIN_LOOP_H |
27 | |
28 | #include "block/aio.h" |
29 | |
30 | #define SIG_IPI SIGUSR1 |
31 | |
32 | /** |
33 | * qemu_init_main_loop: Set up the process so that it can run the main loop. |
34 | * |
35 | * This includes setting up signal handlers. It should be called before |
36 | * any other threads are created. In addition, threads other than the |
37 | * main one should block signals that are trapped by the main loop. |
38 | * For simplicity, you can consider these signals to be safe: SIGUSR1, |
39 | * SIGUSR2, thread signals (SIGFPE, SIGILL, SIGSEGV, SIGBUS) and real-time |
40 | * signals if available. Remember that Windows in practice does not have |
41 | * signals, though. |
42 | * |
43 | * In the case of QEMU tools, this will also start/initialize timers. |
44 | */ |
45 | int qemu_init_main_loop(Error **errp); |
46 | |
47 | /** |
48 | * main_loop_wait: Run one iteration of the main loop. |
49 | * |
50 | * If @nonblocking is true, poll for events, otherwise suspend until |
51 | * one actually occurs. The main loop usually consists of a loop that |
52 | * repeatedly calls main_loop_wait(false). |
53 | * |
54 | * Main loop services include file descriptor callbacks, bottom halves |
55 | * and timers (defined in qemu-timer.h). Bottom halves are similar to timers |
56 | * that execute immediately, but have a lower overhead and scheduling them |
57 | * is wait-free, thread-safe and signal-safe. |
58 | * |
59 | * It is sometimes useful to put a whole program in a coroutine. In this |
60 | * case, the coroutine actually should be started from within the main loop, |
61 | * so that the main loop can run whenever the coroutine yields. To do this, |
62 | * you can use a bottom half to enter the coroutine as soon as the main loop |
63 | * starts: |
64 | * |
65 | * void enter_co_bh(void *opaque) { |
66 | * QEMUCoroutine *co = opaque; |
67 | * qemu_coroutine_enter(co); |
68 | * } |
69 | * |
70 | * ... |
71 | * QEMUCoroutine *co = qemu_coroutine_create(coroutine_entry, NULL); |
72 | * QEMUBH *start_bh = qemu_bh_new(enter_co_bh, co); |
73 | * qemu_bh_schedule(start_bh); |
74 | * while (...) { |
75 | * main_loop_wait(false); |
76 | * } |
77 | * |
78 | * (In the future we may provide a wrapper for this). |
79 | * |
80 | * @nonblocking: Whether the caller should block until an event occurs. |
81 | */ |
82 | void main_loop_wait(int nonblocking); |
83 | |
84 | /** |
85 | * qemu_get_aio_context: Return the main loop's AioContext |
86 | */ |
87 | AioContext *qemu_get_aio_context(void); |
88 | |
89 | /** |
90 | * qemu_notify_event: Force processing of pending events. |
91 | * |
92 | * Similar to signaling a condition variable, qemu_notify_event forces |
93 | * main_loop_wait to look at pending events and exit. The caller of |
94 | * main_loop_wait will usually call it again very soon, so qemu_notify_event |
95 | * also has the side effect of recalculating the sets of file descriptors |
96 | * that the main loop waits for. |
97 | * |
98 | * Calling qemu_notify_event is rarely necessary, because main loop |
99 | * services (bottom halves and timers) call it themselves. |
100 | */ |
101 | void qemu_notify_event(void); |
102 | |
103 | #ifdef _WIN32 |
104 | /* return TRUE if no sleep should be done afterwards */ |
105 | typedef int PollingFunc(void *opaque); |
106 | |
107 | /** |
108 | * qemu_add_polling_cb: Register a Windows-specific polling callback |
109 | * |
110 | * Currently, under Windows some events are polled rather than waited for. |
111 | * Polling callbacks do not ensure that @func is called timely, because |
112 | * the main loop might wait for an arbitrarily long time. If possible, |
113 | * you should instead create a separate thread that does a blocking poll |
114 | * and set a Win32 event object. The event can then be passed to |
115 | * qemu_add_wait_object. |
116 | * |
117 | * Polling callbacks really have nothing Windows specific in them, but |
118 | * as they are a hack and are currently not necessary under POSIX systems, |
119 | * they are only available when QEMU is running under Windows. |
120 | * |
121 | * @func: The function that does the polling, and returns 1 to force |
122 | * immediate completion of main_loop_wait. |
123 | * @opaque: A pointer-size value that is passed to @func. |
124 | */ |
125 | int qemu_add_polling_cb(PollingFunc *func, void *opaque); |
126 | |
127 | /** |
128 | * qemu_del_polling_cb: Unregister a Windows-specific polling callback |
129 | * |
130 | * This function removes a callback that was registered with |
131 | * qemu_add_polling_cb. |
132 | * |
133 | * @func: The function that was passed to qemu_add_polling_cb. |
134 | * @opaque: A pointer-size value that was passed to qemu_add_polling_cb. |
135 | */ |
136 | void qemu_del_polling_cb(PollingFunc *func, void *opaque); |
137 | |
138 | /* Wait objects handling */ |
139 | typedef void WaitObjectFunc(void *opaque); |
140 | |
141 | /** |
142 | * qemu_add_wait_object: Register a callback for a Windows handle |
143 | * |
144 | * Under Windows, the iohandler mechanism can only be used with sockets. |
145 | * QEMU must use the WaitForMultipleObjects API to wait on other handles. |
146 | * This function registers a #HANDLE with QEMU, so that it will be included |
147 | * in the main loop's calls to WaitForMultipleObjects. When the handle |
148 | * is in a signaled state, QEMU will call @func. |
149 | * |
150 | * @handle: The Windows handle to be observed. |
151 | * @func: A function to be called when @handle is in a signaled state. |
152 | * @opaque: A pointer-size value that is passed to @func. |
153 | */ |
154 | int qemu_add_wait_object(HANDLE handle, WaitObjectFunc *func, void *opaque); |
155 | |
156 | /** |
157 | * qemu_del_wait_object: Unregister a callback for a Windows handle |
158 | * |
159 | * This function removes a callback that was registered with |
160 | * qemu_add_wait_object. |
161 | * |
162 | * @func: The function that was passed to qemu_add_wait_object. |
163 | * @opaque: A pointer-size value that was passed to qemu_add_wait_object. |
164 | */ |
165 | void qemu_del_wait_object(HANDLE handle, WaitObjectFunc *func, void *opaque); |
166 | #endif |
167 | |
168 | /* async I/O support */ |
169 | |
170 | typedef void IOReadHandler(void *opaque, const uint8_t *buf, int size); |
171 | |
172 | /** |
173 | * IOCanReadHandler: Return the number of bytes that #IOReadHandler can accept |
174 | * |
175 | * This function reports how many bytes #IOReadHandler is prepared to accept. |
176 | * #IOReadHandler may be invoked with up to this number of bytes. If this |
177 | * function returns 0 then #IOReadHandler is not invoked. |
178 | * |
179 | * This function is typically called from an event loop. If the number of |
180 | * bytes changes outside the event loop (e.g. because a vcpu thread drained the |
181 | * buffer), then it is necessary to kick the event loop so that this function |
182 | * is called again. aio_notify() or qemu_notify_event() can be used to kick |
183 | * the event loop. |
184 | */ |
185 | typedef int IOCanReadHandler(void *opaque); |
186 | |
187 | /** |
188 | * qemu_set_fd_handler: Register a file descriptor with the main loop |
189 | * |
190 | * This function tells the main loop to wake up whenever one of the |
191 | * following conditions is true: |
192 | * |
193 | * 1) if @fd_write is not %NULL, when the file descriptor is writable; |
194 | * |
195 | * 2) if @fd_read is not %NULL, when the file descriptor is readable. |
196 | * |
197 | * The callbacks that are set up by qemu_set_fd_handler are level-triggered. |
198 | * If @fd_read does not read from @fd, or @fd_write does not write to @fd |
199 | * until its buffers are full, they will be called again on the next |
200 | * iteration. |
201 | * |
202 | * @fd: The file descriptor to be observed. Under Windows it must be |
203 | * a #SOCKET. |
204 | * |
205 | * @fd_read: A level-triggered callback that is fired if @fd is readable |
206 | * at the beginning of a main loop iteration, or if it becomes readable |
207 | * during one. |
208 | * |
209 | * @fd_write: A level-triggered callback that is fired when @fd is writable |
210 | * at the beginning of a main loop iteration, or if it becomes writable |
211 | * during one. |
212 | * |
213 | * @opaque: A pointer-sized value that is passed to @fd_read and @fd_write. |
214 | */ |
215 | void qemu_set_fd_handler(int fd, |
216 | IOHandler *fd_read, |
217 | IOHandler *fd_write, |
218 | void *opaque); |
219 | |
220 | |
221 | /** |
222 | * event_notifier_set_handler: Register an EventNotifier with the main loop |
223 | * |
224 | * This function tells the main loop to wake up whenever the |
225 | * #EventNotifier was set. |
226 | * |
227 | * @e: The #EventNotifier to be observed. |
228 | * |
229 | * @handler: A level-triggered callback that is fired when @e |
230 | * has been set. @e is passed to it as a parameter. |
231 | */ |
232 | void event_notifier_set_handler(EventNotifier *e, |
233 | EventNotifierHandler *handler); |
234 | |
235 | GSource *iohandler_get_g_source(void); |
236 | AioContext *iohandler_get_aio_context(void); |
237 | #ifdef CONFIG_POSIX |
238 | /** |
239 | * qemu_add_child_watch: Register a child process for reaping. |
240 | * |
241 | * Under POSIX systems, a parent process must read the exit status of |
242 | * its child processes using waitpid, or the operating system will not |
243 | * free some of the resources attached to that process. |
244 | * |
245 | * This function directs the QEMU main loop to observe a child process |
246 | * and call waitpid as soon as it exits; the watch is then removed |
247 | * automatically. It is useful whenever QEMU forks a child process |
248 | * but will find out about its termination by other means such as a |
249 | * "broken pipe". |
250 | * |
251 | * @pid: The pid that QEMU should observe. |
252 | */ |
253 | int qemu_add_child_watch(pid_t pid); |
254 | #endif |
255 | |
256 | /** |
257 | * qemu_mutex_iothread_locked: Return lock status of the main loop mutex. |
258 | * |
259 | * The main loop mutex is the coarsest lock in QEMU, and as such it |
260 | * must always be taken outside other locks. This function helps |
261 | * functions take different paths depending on whether the current |
262 | * thread is running within the main loop mutex. |
263 | */ |
264 | bool qemu_mutex_iothread_locked(void); |
265 | |
266 | /** |
267 | * qemu_mutex_lock_iothread: Lock the main loop mutex. |
268 | * |
269 | * This function locks the main loop mutex. The mutex is taken by |
270 | * main() in vl.c and always taken except while waiting on |
271 | * external events (such as with select). The mutex should be taken |
272 | * by threads other than the main loop thread when calling |
273 | * qemu_bh_new(), qemu_set_fd_handler() and basically all other |
274 | * functions documented in this file. |
275 | * |
276 | * NOTE: tools currently are single-threaded and qemu_mutex_lock_iothread |
277 | * is a no-op there. |
278 | */ |
279 | #define qemu_mutex_lock_iothread() \ |
280 | qemu_mutex_lock_iothread_impl(__FILE__, __LINE__) |
281 | void qemu_mutex_lock_iothread_impl(const char *file, int line); |
282 | |
283 | /** |
284 | * qemu_mutex_unlock_iothread: Unlock the main loop mutex. |
285 | * |
286 | * This function unlocks the main loop mutex. The mutex is taken by |
287 | * main() in vl.c and always taken except while waiting on |
288 | * external events (such as with select). The mutex should be unlocked |
289 | * as soon as possible by threads other than the main loop thread, |
290 | * because it prevents the main loop from processing callbacks, |
291 | * including timers and bottom halves. |
292 | * |
293 | * NOTE: tools currently are single-threaded and qemu_mutex_unlock_iothread |
294 | * is a no-op there. |
295 | */ |
296 | void qemu_mutex_unlock_iothread(void); |
297 | |
298 | /* internal interfaces */ |
299 | |
300 | void qemu_fd_register(int fd); |
301 | |
302 | QEMUBH *qemu_bh_new(QEMUBHFunc *cb, void *opaque); |
303 | void qemu_bh_schedule_idle(QEMUBH *bh); |
304 | |
305 | enum { |
306 | MAIN_LOOP_POLL_FILL, |
307 | MAIN_LOOP_POLL_ERR, |
308 | MAIN_LOOP_POLL_OK, |
309 | }; |
310 | |
311 | typedef struct MainLoopPoll { |
312 | int state; |
313 | uint32_t timeout; |
314 | GArray *pollfds; |
315 | } MainLoopPoll; |
316 | |
317 | void main_loop_poll_add_notifier(Notifier *notify); |
318 | void main_loop_poll_remove_notifier(Notifier *notify); |
319 | |
320 | #endif |
321 | |