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 */
45int 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 */
82void main_loop_wait(int nonblocking);
83
84/**
85 * qemu_get_aio_context: Return the main loop's AioContext
86 */
87AioContext *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 */
101void qemu_notify_event(void);
102
103#ifdef _WIN32
104/* return TRUE if no sleep should be done afterwards */
105typedef 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 */
125int 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 */
136void qemu_del_polling_cb(PollingFunc *func, void *opaque);
137
138/* Wait objects handling */
139typedef 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 */
154int 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 */
165void qemu_del_wait_object(HANDLE handle, WaitObjectFunc *func, void *opaque);
166#endif
167
168/* async I/O support */
169
170typedef 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 */
185typedef 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 */
215void 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 */
232void event_notifier_set_handler(EventNotifier *e,
233 EventNotifierHandler *handler);
234
235GSource *iohandler_get_g_source(void);
236AioContext *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 */
253int 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 */
264bool 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__)
281void 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 */
296void qemu_mutex_unlock_iothread(void);
297
298/* internal interfaces */
299
300void qemu_fd_register(int fd);
301
302QEMUBH *qemu_bh_new(QEMUBHFunc *cb, void *opaque);
303void qemu_bh_schedule_idle(QEMUBH *bh);
304
305enum {
306 MAIN_LOOP_POLL_FILL,
307 MAIN_LOOP_POLL_ERR,
308 MAIN_LOOP_POLL_OK,
309};
310
311typedef struct MainLoopPoll {
312 int state;
313 uint32_t timeout;
314 GArray *pollfds;
315} MainLoopPoll;
316
317void main_loop_poll_add_notifier(Notifier *notify);
318void main_loop_poll_remove_notifier(Notifier *notify);
319
320#endif
321