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4 * Copyright (c) 2003-2008 Fabrice Bellard
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7 * of this software and associated documentation files (the "Software"), to deal
8 * in the Software without restriction, including without limitation the rights
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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
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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_wait: Run one iteration of the main loop.
48 * If @nonblocking is true, poll for events, otherwise suspend until
49 * one actually occurs. The main loop usually consists of a loop that
50 * repeatedly calls main_loop_wait(false).
52 * Main loop services include file descriptor callbacks, bottom halves
53 * and timers (defined in qemu-timer.h). Bottom halves are similar to timers
54 * that execute immediately, but have a lower overhead and scheduling them
55 * is wait-free, thread-safe and signal-safe.
57 * It is sometimes useful to put a whole program in a coroutine. In this
58 * case, the coroutine actually should be started from within the main loop,
59 * so that the main loop can run whenever the coroutine yields. To do this,
60 * you can use a bottom half to enter the coroutine as soon as the main loop
63 * void enter_co_bh(void *opaque) {
64 * QEMUCoroutine *co = opaque;
65 * qemu_coroutine_enter(co, NULL);
69 * QEMUCoroutine *co = qemu_coroutine_create(coroutine_entry);
70 * QEMUBH *start_bh = qemu_bh_new(enter_co_bh, co);
71 * qemu_bh_schedule(start_bh);
73 * main_loop_wait(false);
76 * (In the future we may provide a wrapper for this).
78 * @nonblocking: Whether the caller should block until an event occurs.
80 int main_loop_wait(int nonblocking
);
83 * qemu_notify_event: Force processing of pending events.
85 * Similar to signaling a condition variable, qemu_notify_event forces
86 * main_loop_wait to look at pending events and exit. The caller of
87 * main_loop_wait will usually call it again very soon, so qemu_notify_event
88 * also has the side effect of recalculating the sets of file descriptors
89 * that the main loop waits for.
91 * Calling qemu_notify_event is rarely necessary, because main loop
92 * services (bottom halves and timers) call it themselves. One notable
93 * exception occurs when using qemu_set_fd_handler2 (see below).
95 void qemu_notify_event(void);
98 /* return TRUE if no sleep should be done afterwards */
99 typedef int PollingFunc(void *opaque
);
102 * qemu_add_polling_cb: Register a Windows-specific polling callback
104 * Currently, under Windows some events are polled rather than waited for.
105 * Polling callbacks do not ensure that @func is called timely, because
106 * the main loop might wait for an arbitrarily long time. If possible,
107 * you should instead create a separate thread that does a blocking poll
108 * and set a Win32 event object. The event can then be passed to
109 * qemu_add_wait_object.
111 * Polling callbacks really have nothing Windows specific in them, but
112 * as they are a hack and are currently not necessary under POSIX systems,
113 * they are only available when QEMU is running under Windows.
115 * @func: The function that does the polling, and returns 1 to force
116 * immediate completion of main_loop_wait.
117 * @opaque: A pointer-size value that is passed to @func.
119 int qemu_add_polling_cb(PollingFunc
*func
, void *opaque
);
122 * qemu_del_polling_cb: Unregister a Windows-specific polling callback
124 * This function removes a callback that was registered with
125 * qemu_add_polling_cb.
127 * @func: The function that was passed to qemu_add_polling_cb.
128 * @opaque: A pointer-size value that was passed to qemu_add_polling_cb.
130 void qemu_del_polling_cb(PollingFunc
*func
, void *opaque
);
132 /* Wait objects handling */
133 typedef void WaitObjectFunc(void *opaque
);
136 * qemu_add_wait_object: Register a callback for a Windows handle
138 * Under Windows, the iohandler mechanism can only be used with sockets.
139 * QEMU must use the WaitForMultipleObjects API to wait on other handles.
140 * This function registers a #HANDLE with QEMU, so that it will be included
141 * in the main loop's calls to WaitForMultipleObjects. When the handle
142 * is in a signaled state, QEMU will call @func.
144 * @handle: The Windows handle to be observed.
145 * @func: A function to be called when @handle is in a signaled state.
146 * @opaque: A pointer-size value that is passed to @func.
148 int qemu_add_wait_object(HANDLE handle
, WaitObjectFunc
*func
, void *opaque
);
151 * qemu_del_wait_object: Unregister a callback for a Windows handle
153 * This function removes a callback that was registered with
154 * qemu_add_wait_object.
156 * @func: The function that was passed to qemu_add_wait_object.
157 * @opaque: A pointer-size value that was passed to qemu_add_wait_object.
159 void qemu_del_wait_object(HANDLE handle
, WaitObjectFunc
*func
, void *opaque
);
162 /* async I/O support */
164 typedef void IOReadHandler(void *opaque
, const uint8_t *buf
, int size
);
165 typedef int IOCanReadHandler(void *opaque
);
166 typedef void IOHandler(void *opaque
);
169 * qemu_set_fd_handler2: Register a file descriptor with the main loop
171 * This function tells the main loop to wake up whenever one of the
172 * following conditions is true:
174 * 1) if @fd_write is not %NULL, when the file descriptor is writable;
176 * 2) if @fd_read is not %NULL, when the file descriptor is readable.
178 * @fd_read_poll can be used to disable the @fd_read callback temporarily.
179 * This is useful to avoid calling qemu_set_fd_handler2 every time the
180 * client becomes interested in reading (or dually, stops being interested).
181 * A typical example is when @fd is a listening socket and you want to bound
182 * the number of active clients. Remember to call qemu_notify_event whenever
183 * the condition may change from %false to %true.
185 * The callbacks that are set up by qemu_set_fd_handler2 are level-triggered.
186 * If @fd_read does not read from @fd, or @fd_write does not write to @fd
187 * until its buffers are full, they will be called again on the next
190 * @fd: The file descriptor to be observed. Under Windows it must be
193 * @fd_read_poll: A function that returns 1 if the @fd_read callback
194 * should be fired. If the function returns 0, the main loop will not
195 * end its iteration even if @fd becomes readable.
197 * @fd_read: A level-triggered callback that is fired if @fd is readable
198 * at the beginning of a main loop iteration, or if it becomes readable
201 * @fd_write: A level-triggered callback that is fired when @fd is writable
202 * at the beginning of a main loop iteration, or if it becomes writable
205 * @opaque: A pointer-sized value that is passed to @fd_read_poll,
206 * @fd_read and @fd_write.
208 int qemu_set_fd_handler2(int fd
,
209 IOCanReadHandler
*fd_read_poll
,
215 * qemu_set_fd_handler: Register a file descriptor with the main loop
217 * This function tells the main loop to wake up whenever one of the
218 * following conditions is true:
220 * 1) if @fd_write is not %NULL, when the file descriptor is writable;
222 * 2) if @fd_read is not %NULL, when the file descriptor is readable.
224 * The callbacks that are set up by qemu_set_fd_handler are level-triggered.
225 * If @fd_read does not read from @fd, or @fd_write does not write to @fd
226 * until its buffers are full, they will be called again on the next
229 * @fd: The file descriptor to be observed. Under Windows it must be
232 * @fd_read: A level-triggered callback that is fired if @fd is readable
233 * at the beginning of a main loop iteration, or if it becomes readable
236 * @fd_write: A level-triggered callback that is fired when @fd is writable
237 * at the beginning of a main loop iteration, or if it becomes writable
240 * @opaque: A pointer-sized value that is passed to @fd_read and @fd_write.
242 int qemu_set_fd_handler(int fd
,
247 typedef struct QEMUBH QEMUBH
;
248 typedef void QEMUBHFunc(void *opaque
);
251 * qemu_bh_new: Allocate a new bottom half structure.
253 * Bottom halves are lightweight callbacks whose invocation is guaranteed
254 * to be wait-free, thread-safe and signal-safe. The #QEMUBH structure
255 * is opaque and must be allocated prior to its use.
257 QEMUBH
*qemu_bh_new(QEMUBHFunc
*cb
, void *opaque
);
260 * qemu_bh_schedule: Schedule a bottom half.
262 * Scheduling a bottom half interrupts the main loop and causes the
263 * execution of the callback that was passed to qemu_bh_new.
265 * Bottom halves that are scheduled from a bottom half handler are instantly
266 * invoked. This can create an infinite loop if a bottom half handler
269 * @bh: The bottom half to be scheduled.
271 void qemu_bh_schedule(QEMUBH
*bh
);
274 * qemu_bh_cancel: Cancel execution of a bottom half.
276 * Canceling execution of a bottom half undoes the effect of calls to
277 * qemu_bh_schedule without freeing its resources yet. While cancellation
278 * itself is also wait-free and thread-safe, it can of course race with the
279 * loop that executes bottom halves unless you are holding the iothread
280 * mutex. This makes it mostly useless if you are not holding the mutex.
282 * @bh: The bottom half to be canceled.
284 void qemu_bh_cancel(QEMUBH
*bh
);
287 *qemu_bh_delete: Cancel execution of a bottom half and free its resources.
289 * Deleting a bottom half frees the memory that was allocated for it by
290 * qemu_bh_new. It also implies canceling the bottom half if it was
293 * @bh: The bottom half to be deleted.
295 void qemu_bh_delete(QEMUBH
*bh
);
299 * qemu_add_child_watch: Register a child process for reaping.
301 * Under POSIX systems, a parent process must read the exit status of
302 * its child processes using waitpid, or the operating system will not
303 * free some of the resources attached to that process.
305 * This function directs the QEMU main loop to observe a child process
306 * and call waitpid as soon as it exits; the watch is then removed
307 * automatically. It is useful whenever QEMU forks a child process
308 * but will find out about its termination by other means such as a
311 * @pid: The pid that QEMU should observe.
313 int qemu_add_child_watch(pid_t pid
);
317 * qemu_mutex_lock_iothread: Lock the main loop mutex.
319 * This function locks the main loop mutex. The mutex is taken by
320 * qemu_init_main_loop and always taken except while waiting on
321 * external events (such as with select). The mutex should be taken
322 * by threads other than the main loop thread when calling
323 * qemu_bh_new(), qemu_set_fd_handler() and basically all other
324 * functions documented in this file.
326 * NOTE: tools currently are single-threaded and qemu_mutex_lock_iothread
329 void qemu_mutex_lock_iothread(void);
332 * qemu_mutex_unlock_iothread: Unlock the main loop mutex.
334 * This function unlocks the main loop mutex. The mutex is taken by
335 * qemu_init_main_loop and always taken except while waiting on
336 * external events (such as with select). The mutex should be unlocked
337 * as soon as possible by threads other than the main loop thread,
338 * because it prevents the main loop from processing callbacks,
339 * including timers and bottom halves.
341 * NOTE: tools currently are single-threaded and qemu_mutex_unlock_iothread
344 void qemu_mutex_unlock_iothread(void);
346 /* internal interfaces */
348 void qemu_fd_register(int fd
);
349 void qemu_iohandler_fill(int *pnfds
, fd_set
*readfds
, fd_set
*writefds
, fd_set
*xfds
);
350 void qemu_iohandler_poll(fd_set
*readfds
, fd_set
*writefds
, fd_set
*xfds
, int rc
);
352 void qemu_bh_schedule_idle(QEMUBH
*bh
);
353 int qemu_bh_poll(void);
354 void qemu_bh_update_timeout(uint32_t *timeout
);