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
25 #ifndef QEMU_MAIN_LOOP_H
26 #define QEMU_MAIN_LOOP_H 1
28 #include "block/aio.h"
30 #define SIG_IPI SIGUSR1
33 * qemu_init_main_loop: Set up the process so that it can run the main loop.
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
43 * In the case of QEMU tools, this will also start/initialize timers.
45 int qemu_init_main_loop(void);
48 * main_loop_wait: Run one iteration of the main loop.
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).
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.
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
65 * void enter_co_bh(void *opaque) {
66 * QEMUCoroutine *co = opaque;
67 * qemu_coroutine_enter(co, NULL);
71 * QEMUCoroutine *co = qemu_coroutine_create(coroutine_entry);
72 * QEMUBH *start_bh = qemu_bh_new(enter_co_bh, co);
73 * qemu_bh_schedule(start_bh);
75 * main_loop_wait(false);
78 * (In the future we may provide a wrapper for this).
80 * @nonblocking: Whether the caller should block until an event occurs.
82 int main_loop_wait(int nonblocking);
85 * qemu_get_aio_context: Return the main loop's AioContext
87 AioContext *qemu_get_aio_context(void);
90 * qemu_notify_event: Force processing of pending events.
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.
98 * Calling qemu_notify_event is rarely necessary, because main loop
99 * services (bottom halves and timers) call it themselves. One notable
100 * exception occurs when using qemu_set_fd_handler2 (see below).
102 void qemu_notify_event(void);
104 // TODO: Mark HAX related code...
105 #ifdef CONFIG_HAX_BACKEND
106 void qemu_notify_hax_event(void);
108 static inline void qemu_notify_hax_event(void)
115 /* return TRUE if no sleep should be done afterwards */
116 typedef int PollingFunc(void *opaque);
119 * qemu_add_polling_cb: Register a Windows-specific polling callback
121 * Currently, under Windows some events are polled rather than waited for.
122 * Polling callbacks do not ensure that @func is called timely, because
123 * the main loop might wait for an arbitrarily long time. If possible,
124 * you should instead create a separate thread that does a blocking poll
125 * and set a Win32 event object. The event can then be passed to
126 * qemu_add_wait_object.
128 * Polling callbacks really have nothing Windows specific in them, but
129 * as they are a hack and are currently not necessary under POSIX systems,
130 * they are only available when QEMU is running under Windows.
132 * @func: The function that does the polling, and returns 1 to force
133 * immediate completion of main_loop_wait.
134 * @opaque: A pointer-size value that is passed to @func.
136 int qemu_add_polling_cb(PollingFunc *func, void *opaque);
139 * qemu_del_polling_cb: Unregister a Windows-specific polling callback
141 * This function removes a callback that was registered with
142 * qemu_add_polling_cb.
144 * @func: The function that was passed to qemu_add_polling_cb.
145 * @opaque: A pointer-size value that was passed to qemu_add_polling_cb.
147 void qemu_del_polling_cb(PollingFunc *func, void *opaque);
149 /* Wait objects handling */
150 typedef void WaitObjectFunc(void *opaque);
153 * qemu_add_wait_object: Register a callback for a Windows handle
155 * Under Windows, the iohandler mechanism can only be used with sockets.
156 * QEMU must use the WaitForMultipleObjects API to wait on other handles.
157 * This function registers a #HANDLE with QEMU, so that it will be included
158 * in the main loop's calls to WaitForMultipleObjects. When the handle
159 * is in a signaled state, QEMU will call @func.
161 * @handle: The Windows handle to be observed.
162 * @func: A function to be called when @handle is in a signaled state.
163 * @opaque: A pointer-size value that is passed to @func.
165 int qemu_add_wait_object(HANDLE handle, WaitObjectFunc *func, void *opaque);
168 * qemu_del_wait_object: Unregister a callback for a Windows handle
170 * This function removes a callback that was registered with
171 * qemu_add_wait_object.
173 * @func: The function that was passed to qemu_add_wait_object.
174 * @opaque: A pointer-size value that was passed to qemu_add_wait_object.
176 void qemu_del_wait_object(HANDLE handle, WaitObjectFunc *func, void *opaque);
179 /* async I/O support */
181 typedef void IOReadHandler(void *opaque, const uint8_t *buf, int size);
182 typedef int IOCanReadHandler(void *opaque);
185 * qemu_set_fd_handler2: Register a file descriptor with the main loop
187 * This function tells the main loop to wake up whenever one of the
188 * following conditions is true:
190 * 1) if @fd_write is not %NULL, when the file descriptor is writable;
192 * 2) if @fd_read is not %NULL, when the file descriptor is readable.
194 * @fd_read_poll can be used to disable the @fd_read callback temporarily.
195 * This is useful to avoid calling qemu_set_fd_handler2 every time the
196 * client becomes interested in reading (or dually, stops being interested).
197 * A typical example is when @fd is a listening socket and you want to bound
198 * the number of active clients. Remember to call qemu_notify_event whenever
199 * the condition may change from %false to %true.
201 * The callbacks that are set up by qemu_set_fd_handler2 are level-triggered.
202 * If @fd_read does not read from @fd, or @fd_write does not write to @fd
203 * until its buffers are full, they will be called again on the next
206 * @fd: The file descriptor to be observed. Under Windows it must be
209 * @fd_read_poll: A function that returns 1 if the @fd_read callback
210 * should be fired. If the function returns 0, the main loop will not
211 * end its iteration even if @fd becomes readable.
213 * @fd_read: A level-triggered callback that is fired if @fd is readable
214 * at the beginning of a main loop iteration, or if it becomes readable
217 * @fd_write: A level-triggered callback that is fired when @fd is writable
218 * at the beginning of a main loop iteration, or if it becomes writable
221 * @opaque: A pointer-sized value that is passed to @fd_read_poll,
222 * @fd_read and @fd_write.
224 int qemu_set_fd_handler2(int fd,
225 IOCanReadHandler *fd_read_poll,
231 * qemu_set_fd_handler: Register a file descriptor with the main loop
233 * This function tells the main loop to wake up whenever one of the
234 * following conditions is true:
236 * 1) if @fd_write is not %NULL, when the file descriptor is writable;
238 * 2) if @fd_read is not %NULL, when the file descriptor is readable.
240 * The callbacks that are set up by qemu_set_fd_handler are level-triggered.
241 * If @fd_read does not read from @fd, or @fd_write does not write to @fd
242 * until its buffers are full, they will be called again on the next
245 * @fd: The file descriptor to be observed. Under Windows it must be
248 * @fd_read: A level-triggered callback that is fired if @fd is readable
249 * at the beginning of a main loop iteration, or if it becomes readable
252 * @fd_write: A level-triggered callback that is fired when @fd is writable
253 * at the beginning of a main loop iteration, or if it becomes writable
256 * @opaque: A pointer-sized value that is passed to @fd_read and @fd_write.
258 int qemu_set_fd_handler(int fd,
265 * qemu_add_child_watch: Register a child process for reaping.
267 * Under POSIX systems, a parent process must read the exit status of
268 * its child processes using waitpid, or the operating system will not
269 * free some of the resources attached to that process.
271 * This function directs the QEMU main loop to observe a child process
272 * and call waitpid as soon as it exits; the watch is then removed
273 * automatically. It is useful whenever QEMU forks a child process
274 * but will find out about its termination by other means such as a
277 * @pid: The pid that QEMU should observe.
279 int qemu_add_child_watch(pid_t pid);
283 * qemu_mutex_lock_iothread: Lock the main loop mutex.
285 * This function locks the main loop mutex. The mutex is taken by
286 * qemu_init_main_loop and always taken except while waiting on
287 * external events (such as with select). The mutex should be taken
288 * by threads other than the main loop thread when calling
289 * qemu_bh_new(), qemu_set_fd_handler() and basically all other
290 * functions documented in this file.
292 * NOTE: tools currently are single-threaded and qemu_mutex_lock_iothread
295 void qemu_mutex_lock_iothread(void);
298 * qemu_mutex_unlock_iothread: Unlock the main loop mutex.
300 * This function unlocks the main loop mutex. The mutex is taken by
301 * qemu_init_main_loop and always taken except while waiting on
302 * external events (such as with select). The mutex should be unlocked
303 * as soon as possible by threads other than the main loop thread,
304 * because it prevents the main loop from processing callbacks,
305 * including timers and bottom halves.
307 * NOTE: tools currently are single-threaded and qemu_mutex_unlock_iothread
310 void qemu_mutex_unlock_iothread(void);
312 /* internal interfaces */
314 void qemu_fd_register(int fd);
315 void qemu_iohandler_fill(GArray *pollfds);
316 void qemu_iohandler_poll(GArray *pollfds, int rc);
318 QEMUBH *qemu_bh_new(QEMUBHFunc *cb, void *opaque);
319 void qemu_bh_schedule_idle(QEMUBH *bh);