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 #define SIG_IPI SIGUSR1
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
41 * In the case of QEMU tools, this will also start/initialize timers.
43 int qemu_init_main_loop(void);
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);
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
73 * void enter_co_bh(void *opaque) {
74 * QEMUCoroutine *co = opaque;
75 * qemu_coroutine_enter(co, NULL);
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);
83 * main_loop_wait(false);
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);
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 // TODO: Mark HAX related code...
108 #ifdef CONFIG_HAX_BACKEND
109 void qemu_notify_hax_event(void);
111 static inline void qemu_notify_hax_event(void)
118 /* return TRUE if no sleep should be done afterwards */
119 typedef int PollingFunc(void *opaque);
122 * qemu_add_polling_cb: Register a Windows-specific polling callback
124 * Currently, under Windows some events are polled rather than waited for.
125 * Polling callbacks do not ensure that @func is called timely, because
126 * the main loop might wait for an arbitrarily long time. If possible,
127 * you should instead create a separate thread that does a blocking poll
128 * and set a Win32 event object. The event can then be passed to
129 * qemu_add_wait_object.
131 * Polling callbacks really have nothing Windows specific in them, but
132 * as they are a hack and are currently not necessary under POSIX systems,
133 * they are only available when QEMU is running under Windows.
135 * @func: The function that does the polling, and returns 1 to force
136 * immediate completion of main_loop_wait.
137 * @opaque: A pointer-size value that is passed to @func.
139 int qemu_add_polling_cb(PollingFunc *func, void *opaque);
142 * qemu_del_polling_cb: Unregister a Windows-specific polling callback
144 * This function removes a callback that was registered with
145 * qemu_add_polling_cb.
147 * @func: The function that was passed to qemu_add_polling_cb.
148 * @opaque: A pointer-size value that was passed to qemu_add_polling_cb.
150 void qemu_del_polling_cb(PollingFunc *func, void *opaque);
152 /* Wait objects handling */
153 typedef void WaitObjectFunc(void *opaque);
156 * qemu_add_wait_object: Register a callback for a Windows handle
158 * Under Windows, the iohandler mechanism can only be used with sockets.
159 * QEMU must use the WaitForMultipleObjects API to wait on other handles.
160 * This function registers a #HANDLE with QEMU, so that it will be included
161 * in the main loop's calls to WaitForMultipleObjects. When the handle
162 * is in a signaled state, QEMU will call @func.
164 * @handle: The Windows handle to be observed.
165 * @func: A function to be called when @handle is in a signaled state.
166 * @opaque: A pointer-size value that is passed to @func.
168 int qemu_add_wait_object(HANDLE handle, WaitObjectFunc *func, void *opaque);
171 * qemu_del_wait_object: Unregister a callback for a Windows handle
173 * This function removes a callback that was registered with
174 * qemu_add_wait_object.
176 * @func: The function that was passed to qemu_add_wait_object.
177 * @opaque: A pointer-size value that was passed to qemu_add_wait_object.
179 void qemu_del_wait_object(HANDLE handle, WaitObjectFunc *func, void *opaque);
182 /* async I/O support */
184 typedef void IOReadHandler(void *opaque, const uint8_t *buf, int size);
185 typedef int IOCanReadHandler(void *opaque);
186 typedef void IOHandler(void *opaque);
189 * qemu_set_fd_handler2: Register a file descriptor with the main loop
191 * This function tells the main loop to wake up whenever one of the
192 * following conditions is true:
194 * 1) if @fd_write is not %NULL, when the file descriptor is writable;
196 * 2) if @fd_read is not %NULL, when the file descriptor is readable.
198 * @fd_read_poll can be used to disable the @fd_read callback temporarily.
199 * This is useful to avoid calling qemu_set_fd_handler2 every time the
200 * client becomes interested in reading (or dually, stops being interested).
201 * A typical example is when @fd is a listening socket and you want to bound
202 * the number of active clients. Remember to call qemu_notify_event whenever
203 * the condition may change from %false to %true.
205 * The callbacks that are set up by qemu_set_fd_handler2 are level-triggered.
206 * If @fd_read does not read from @fd, or @fd_write does not write to @fd
207 * until its buffers are full, they will be called again on the next
210 * @fd: The file descriptor to be observed. Under Windows it must be
213 * @fd_read_poll: A function that returns 1 if the @fd_read callback
214 * should be fired. If the function returns 0, the main loop will not
215 * end its iteration even if @fd becomes readable.
217 * @fd_read: A level-triggered callback that is fired if @fd is readable
218 * at the beginning of a main loop iteration, or if it becomes readable
221 * @fd_write: A level-triggered callback that is fired when @fd is writable
222 * at the beginning of a main loop iteration, or if it becomes writable
225 * @opaque: A pointer-sized value that is passed to @fd_read_poll,
226 * @fd_read and @fd_write.
228 int qemu_set_fd_handler2(int fd,
229 IOCanReadHandler *fd_read_poll,
235 * qemu_set_fd_handler: Register a file descriptor with the main loop
237 * This function tells the main loop to wake up whenever one of the
238 * following conditions is true:
240 * 1) if @fd_write is not %NULL, when the file descriptor is writable;
242 * 2) if @fd_read is not %NULL, when the file descriptor is readable.
244 * The callbacks that are set up by qemu_set_fd_handler are level-triggered.
245 * If @fd_read does not read from @fd, or @fd_write does not write to @fd
246 * until its buffers are full, they will be called again on the next
249 * @fd: The file descriptor to be observed. Under Windows it must be
252 * @fd_read: A level-triggered callback that is fired if @fd is readable
253 * at the beginning of a main loop iteration, or if it becomes readable
256 * @fd_write: A level-triggered callback that is fired when @fd is writable
257 * at the beginning of a main loop iteration, or if it becomes writable
260 * @opaque: A pointer-sized value that is passed to @fd_read and @fd_write.
262 int qemu_set_fd_handler(int fd,
267 typedef struct QEMUBH QEMUBH;
268 typedef void QEMUBHFunc(void *opaque);
271 * qemu_bh_new: Allocate a new bottom half structure.
273 * Bottom halves are lightweight callbacks whose invocation is guaranteed
274 * to be wait-free, thread-safe and signal-safe. The #QEMUBH structure
275 * is opaque and must be allocated prior to its use.
277 QEMUBH *qemu_bh_new(QEMUBHFunc *cb, void *opaque);
280 * qemu_bh_schedule: Schedule a bottom half.
282 * Scheduling a bottom half interrupts the main loop and causes the
283 * execution of the callback that was passed to qemu_bh_new.
285 * Bottom halves that are scheduled from a bottom half handler are instantly
286 * invoked. This can create an infinite loop if a bottom half handler
289 * @bh: The bottom half to be scheduled.
291 void qemu_bh_schedule(QEMUBH *bh);
294 * qemu_bh_cancel: Cancel execution of a bottom half.
296 * Canceling execution of a bottom half undoes the effect of calls to
297 * qemu_bh_schedule without freeing its resources yet. While cancellation
298 * itself is also wait-free and thread-safe, it can of course race with the
299 * loop that executes bottom halves unless you are holding the iothread
300 * mutex. This makes it mostly useless if you are not holding the mutex.
302 * @bh: The bottom half to be canceled.
304 void qemu_bh_cancel(QEMUBH *bh);
307 *qemu_bh_delete: Cancel execution of a bottom half and free its resources.
309 * Deleting a bottom half frees the memory that was allocated for it by
310 * qemu_bh_new. It also implies canceling the bottom half if it was
313 * @bh: The bottom half to be deleted.
315 void qemu_bh_delete(QEMUBH *bh);
319 * qemu_add_child_watch: Register a child process for reaping.
321 * Under POSIX systems, a parent process must read the exit status of
322 * its child processes using waitpid, or the operating system will not
323 * free some of the resources attached to that process.
325 * This function directs the QEMU main loop to observe a child process
326 * and call waitpid as soon as it exits; the watch is then removed
327 * automatically. It is useful whenever QEMU forks a child process
328 * but will find out about its termination by other means such as a
331 * @pid: The pid that QEMU should observe.
333 int qemu_add_child_watch(pid_t pid);
337 * qemu_mutex_lock_iothread: Lock the main loop mutex.
339 * This function locks the main loop mutex. The mutex is taken by
340 * qemu_init_main_loop and always taken except while waiting on
341 * external events (such as with select). The mutex should be taken
342 * by threads other than the main loop thread when calling
343 * qemu_bh_new(), qemu_set_fd_handler() and basically all other
344 * functions documented in this file.
346 * NOTE: tools currently are single-threaded and qemu_mutex_lock_iothread
349 void qemu_mutex_lock_iothread(void);
352 * qemu_mutex_unlock_iothread: Unlock the main loop mutex.
354 * This function unlocks the main loop mutex. The mutex is taken by
355 * qemu_init_main_loop and always taken except while waiting on
356 * external events (such as with select). The mutex should be unlocked
357 * as soon as possible by threads other than the main loop thread,
358 * because it prevents the main loop from processing callbacks,
359 * including timers and bottom halves.
361 * NOTE: tools currently are single-threaded and qemu_mutex_unlock_iothread
364 void qemu_mutex_unlock_iothread(void);
366 /* internal interfaces */
368 void qemu_fd_register(int fd);
369 void qemu_iohandler_fill(int *pnfds, fd_set *readfds, fd_set *writefds, fd_set *xfds);
370 void qemu_iohandler_poll(fd_set *readfds, fd_set *writefds, fd_set *xfds, int rc);
372 void qemu_bh_schedule_idle(QEMUBH *bh);
373 int qemu_bh_poll(void);
374 void qemu_bh_update_timeout(uint32_t *timeout);