Merge branch 's390-for-upstream' of git://repo.or.cz/qemu/agraf
[qemu.git] / main-loop.h
blobdce1cd9d7cab443aca8a563322c7881586cf8605
1 /*
2 * QEMU System Emulator
4 * Copyright (c) 2003-2008 Fabrice Bellard
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:
13 * The above copyright notice and this permission notice shall be included in
14 * all copies or substantial portions of the Software.
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.
25 #ifndef QEMU_MAIN_LOOP_H
26 #define QEMU_MAIN_LOOP_H 1
28 #define SIG_IPI SIGUSR1
30 /**
31 * qemu_init_main_loop: Set up the process so that it can run the main loop.
33 * This includes setting up signal handlers. It should be called before
34 * any other threads are created. In addition, threads other than the
35 * main one should block signals that are trapped by the main loop.
36 * For simplicity, you can consider these signals to be safe: SIGUSR1,
37 * SIGUSR2, thread signals (SIGFPE, SIGILL, SIGSEGV, SIGBUS) and real-time
38 * signals if available. Remember that Windows in practice does not have
39 * signals, though.
41 * In the case of QEMU tools, this will also start/initialize timers.
43 int qemu_init_main_loop(void);
45 /**
46 * main_loop_init: Initializes main loop
48 * Internal (but shared for compatibility reasons) initialization routine
49 * for the main loop. This should not be used by applications directly,
50 * use qemu_init_main_loop() instead.
53 int main_loop_init(void);
55 /**
56 * main_loop_wait: Run one iteration of the main loop.
58 * If @nonblocking is true, poll for events, otherwise suspend until
59 * one actually occurs. The main loop usually consists of a loop that
60 * repeatedly calls main_loop_wait(false).
62 * Main loop services include file descriptor callbacks, bottom halves
63 * and timers (defined in qemu-timer.h). Bottom halves are similar to timers
64 * that execute immediately, but have a lower overhead and scheduling them
65 * is wait-free, thread-safe and signal-safe.
67 * It is sometimes useful to put a whole program in a coroutine. In this
68 * case, the coroutine actually should be started from within the main loop,
69 * so that the main loop can run whenever the coroutine yields. To do this,
70 * you can use a bottom half to enter the coroutine as soon as the main loop
71 * starts:
73 * void enter_co_bh(void *opaque) {
74 * QEMUCoroutine *co = opaque;
75 * qemu_coroutine_enter(co, NULL);
76 * }
78 * ...
79 * QEMUCoroutine *co = qemu_coroutine_create(coroutine_entry);
80 * QEMUBH *start_bh = qemu_bh_new(enter_co_bh, co);
81 * qemu_bh_schedule(start_bh);
82 * while (...) {
83 * main_loop_wait(false);
84 * }
86 * (In the future we may provide a wrapper for this).
88 * @nonblocking: Whether the caller should block until an event occurs.
90 int main_loop_wait(int nonblocking);
92 /**
93 * qemu_notify_event: Force processing of pending events.
95 * Similar to signaling a condition variable, qemu_notify_event forces
96 * main_loop_wait to look at pending events and exit. The caller of
97 * main_loop_wait will usually call it again very soon, so qemu_notify_event
98 * also has the side effect of recalculating the sets of file descriptors
99 * that the main loop waits for.
101 * Calling qemu_notify_event is rarely necessary, because main loop
102 * services (bottom halves and timers) call it themselves. One notable
103 * exception occurs when using qemu_set_fd_handler2 (see below).
105 void qemu_notify_event(void);
107 #ifdef _WIN32
108 /* return TRUE if no sleep should be done afterwards */
109 typedef int PollingFunc(void *opaque);
112 * qemu_add_polling_cb: Register a Windows-specific polling callback
114 * Currently, under Windows some events are polled rather than waited for.
115 * Polling callbacks do not ensure that @func is called timely, because
116 * the main loop might wait for an arbitrarily long time. If possible,
117 * you should instead create a separate thread that does a blocking poll
118 * and set a Win32 event object. The event can then be passed to
119 * qemu_add_wait_object.
121 * Polling callbacks really have nothing Windows specific in them, but
122 * as they are a hack and are currently not necessary under POSIX systems,
123 * they are only available when QEMU is running under Windows.
125 * @func: The function that does the polling, and returns 1 to force
126 * immediate completion of main_loop_wait.
127 * @opaque: A pointer-size value that is passed to @func.
129 int qemu_add_polling_cb(PollingFunc *func, void *opaque);
132 * qemu_del_polling_cb: Unregister a Windows-specific polling callback
134 * This function removes a callback that was registered with
135 * qemu_add_polling_cb.
137 * @func: The function that was passed to qemu_add_polling_cb.
138 * @opaque: A pointer-size value that was passed to qemu_add_polling_cb.
140 void qemu_del_polling_cb(PollingFunc *func, void *opaque);
142 /* Wait objects handling */
143 typedef void WaitObjectFunc(void *opaque);
146 * qemu_add_wait_object: Register a callback for a Windows handle
148 * Under Windows, the iohandler mechanism can only be used with sockets.
149 * QEMU must use the WaitForMultipleObjects API to wait on other handles.
150 * This function registers a #HANDLE with QEMU, so that it will be included
151 * in the main loop's calls to WaitForMultipleObjects. When the handle
152 * is in a signaled state, QEMU will call @func.
154 * @handle: The Windows handle to be observed.
155 * @func: A function to be called when @handle is in a signaled state.
156 * @opaque: A pointer-size value that is passed to @func.
158 int qemu_add_wait_object(HANDLE handle, WaitObjectFunc *func, void *opaque);
161 * qemu_del_wait_object: Unregister a callback for a Windows handle
163 * This function removes a callback that was registered with
164 * qemu_add_wait_object.
166 * @func: The function that was passed to qemu_add_wait_object.
167 * @opaque: A pointer-size value that was passed to qemu_add_wait_object.
169 void qemu_del_wait_object(HANDLE handle, WaitObjectFunc *func, void *opaque);
170 #endif
172 /* async I/O support */
174 typedef void IOReadHandler(void *opaque, const uint8_t *buf, int size);
175 typedef int IOCanReadHandler(void *opaque);
176 typedef void IOHandler(void *opaque);
179 * qemu_set_fd_handler2: Register a file descriptor with the main loop
181 * This function tells the main loop to wake up whenever one of the
182 * following conditions is true:
184 * 1) if @fd_write is not %NULL, when the file descriptor is writable;
186 * 2) if @fd_read is not %NULL, when the file descriptor is readable.
188 * @fd_read_poll can be used to disable the @fd_read callback temporarily.
189 * This is useful to avoid calling qemu_set_fd_handler2 every time the
190 * client becomes interested in reading (or dually, stops being interested).
191 * A typical example is when @fd is a listening socket and you want to bound
192 * the number of active clients. Remember to call qemu_notify_event whenever
193 * the condition may change from %false to %true.
195 * The callbacks that are set up by qemu_set_fd_handler2 are level-triggered.
196 * If @fd_read does not read from @fd, or @fd_write does not write to @fd
197 * until its buffers are full, they will be called again on the next
198 * iteration.
200 * @fd: The file descriptor to be observed. Under Windows it must be
201 * a #SOCKET.
203 * @fd_read_poll: A function that returns 1 if the @fd_read callback
204 * should be fired. If the function returns 0, the main loop will not
205 * end its iteration even if @fd becomes readable.
207 * @fd_read: A level-triggered callback that is fired if @fd is readable
208 * at the beginning of a main loop iteration, or if it becomes readable
209 * during one.
211 * @fd_write: A level-triggered callback that is fired when @fd is writable
212 * at the beginning of a main loop iteration, or if it becomes writable
213 * during one.
215 * @opaque: A pointer-sized value that is passed to @fd_read_poll,
216 * @fd_read and @fd_write.
218 int qemu_set_fd_handler2(int fd,
219 IOCanReadHandler *fd_read_poll,
220 IOHandler *fd_read,
221 IOHandler *fd_write,
222 void *opaque);
225 * qemu_set_fd_handler: Register a file descriptor with the main loop
227 * This function tells the main loop to wake up whenever one of the
228 * following conditions is true:
230 * 1) if @fd_write is not %NULL, when the file descriptor is writable;
232 * 2) if @fd_read is not %NULL, when the file descriptor is readable.
234 * The callbacks that are set up by qemu_set_fd_handler are level-triggered.
235 * If @fd_read does not read from @fd, or @fd_write does not write to @fd
236 * until its buffers are full, they will be called again on the next
237 * iteration.
239 * @fd: The file descriptor to be observed. Under Windows it must be
240 * a #SOCKET.
242 * @fd_read: A level-triggered callback that is fired if @fd is readable
243 * at the beginning of a main loop iteration, or if it becomes readable
244 * during one.
246 * @fd_write: A level-triggered callback that is fired when @fd is writable
247 * at the beginning of a main loop iteration, or if it becomes writable
248 * during one.
250 * @opaque: A pointer-sized value that is passed to @fd_read and @fd_write.
252 int qemu_set_fd_handler(int fd,
253 IOHandler *fd_read,
254 IOHandler *fd_write,
255 void *opaque);
257 typedef struct QEMUBH QEMUBH;
258 typedef void QEMUBHFunc(void *opaque);
261 * qemu_bh_new: Allocate a new bottom half structure.
263 * Bottom halves are lightweight callbacks whose invocation is guaranteed
264 * to be wait-free, thread-safe and signal-safe. The #QEMUBH structure
265 * is opaque and must be allocated prior to its use.
267 QEMUBH *qemu_bh_new(QEMUBHFunc *cb, void *opaque);
270 * qemu_bh_schedule: Schedule a bottom half.
272 * Scheduling a bottom half interrupts the main loop and causes the
273 * execution of the callback that was passed to qemu_bh_new.
275 * Bottom halves that are scheduled from a bottom half handler are instantly
276 * invoked. This can create an infinite loop if a bottom half handler
277 * schedules itself.
279 * @bh: The bottom half to be scheduled.
281 void qemu_bh_schedule(QEMUBH *bh);
284 * qemu_bh_cancel: Cancel execution of a bottom half.
286 * Canceling execution of a bottom half undoes the effect of calls to
287 * qemu_bh_schedule without freeing its resources yet. While cancellation
288 * itself is also wait-free and thread-safe, it can of course race with the
289 * loop that executes bottom halves unless you are holding the iothread
290 * mutex. This makes it mostly useless if you are not holding the mutex.
292 * @bh: The bottom half to be canceled.
294 void qemu_bh_cancel(QEMUBH *bh);
297 *qemu_bh_delete: Cancel execution of a bottom half and free its resources.
299 * Deleting a bottom half frees the memory that was allocated for it by
300 * qemu_bh_new. It also implies canceling the bottom half if it was
301 * scheduled.
303 * @bh: The bottom half to be deleted.
305 void qemu_bh_delete(QEMUBH *bh);
307 #ifdef CONFIG_POSIX
309 * qemu_add_child_watch: Register a child process for reaping.
311 * Under POSIX systems, a parent process must read the exit status of
312 * its child processes using waitpid, or the operating system will not
313 * free some of the resources attached to that process.
315 * This function directs the QEMU main loop to observe a child process
316 * and call waitpid as soon as it exits; the watch is then removed
317 * automatically. It is useful whenever QEMU forks a child process
318 * but will find out about its termination by other means such as a
319 * "broken pipe".
321 * @pid: The pid that QEMU should observe.
323 int qemu_add_child_watch(pid_t pid);
324 #endif
327 * qemu_mutex_lock_iothread: Lock the main loop mutex.
329 * This function locks the main loop mutex. The mutex is taken by
330 * qemu_init_main_loop and always taken except while waiting on
331 * external events (such as with select). The mutex should be taken
332 * by threads other than the main loop thread when calling
333 * qemu_bh_new(), qemu_set_fd_handler() and basically all other
334 * functions documented in this file.
336 * NOTE: tools currently are single-threaded and qemu_mutex_lock_iothread
337 * is a no-op there.
339 void qemu_mutex_lock_iothread(void);
342 * qemu_mutex_unlock_iothread: Unlock the main loop mutex.
344 * This function unlocks the main loop mutex. The mutex is taken by
345 * qemu_init_main_loop and always taken except while waiting on
346 * external events (such as with select). The mutex should be unlocked
347 * as soon as possible by threads other than the main loop thread,
348 * because it prevents the main loop from processing callbacks,
349 * including timers and bottom halves.
351 * NOTE: tools currently are single-threaded and qemu_mutex_unlock_iothread
352 * is a no-op there.
354 void qemu_mutex_unlock_iothread(void);
356 /* internal interfaces */
358 void qemu_fd_register(int fd);
359 void qemu_iohandler_fill(int *pnfds, fd_set *readfds, fd_set *writefds, fd_set *xfds);
360 void qemu_iohandler_poll(fd_set *readfds, fd_set *writefds, fd_set *xfds, int rc);
362 void qemu_bh_schedule_idle(QEMUBH *bh);
363 int qemu_bh_poll(void);
364 void qemu_bh_update_timeout(uint32_t *timeout);
366 #endif