sysbus: apic: ioapic: convert to QEMU Object Model
[qemu.git] / main-loop.h
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 1
27
28 #ifdef SIGRTMIN
29 #define SIG_IPI (SIGRTMIN+4)
30 #else
31 #define SIG_IPI SIGUSR1
32 #endif
33
34 /**
35 * qemu_init_main_loop: Set up the process so that it can run the main loop.
36 *
37 * This includes setting up signal handlers. It should be called before
38 * any other threads are created. In addition, threads other than the
39 * main one should block signals that are trapped by the main loop.
40 * For simplicity, you can consider these signals to be safe: SIGUSR1,
41 * SIGUSR2, thread signals (SIGFPE, SIGILL, SIGSEGV, SIGBUS) and real-time
42 * signals if available. Remember that Windows in practice does not have
43 * signals, though.
44 */
45 int qemu_init_main_loop(void);
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, NULL);
68 * }
69 *
70 * ...
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);
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 */
82 int main_loop_wait(int nonblocking);
83
84 /**
85 * qemu_notify_event: Force processing of pending events.
86 *
87 * Similar to signaling a condition variable, qemu_notify_event forces
88 * main_loop_wait to look at pending events and exit. The caller of
89 * main_loop_wait will usually call it again very soon, so qemu_notify_event
90 * also has the side effect of recalculating the sets of file descriptors
91 * that the main loop waits for.
92 *
93 * Calling qemu_notify_event is rarely necessary, because main loop
94 * services (bottom halves and timers) call it themselves. One notable
95 * exception occurs when using qemu_set_fd_handler2 (see below).
96 */
97 void qemu_notify_event(void);
98
99 #ifdef _WIN32
100 /* return TRUE if no sleep should be done afterwards */
101 typedef int PollingFunc(void *opaque);
102
103 /**
104 * qemu_add_polling_cb: Register a Windows-specific polling callback
105 *
106 * Currently, under Windows some events are polled rather than waited for.
107 * Polling callbacks do not ensure that @func is called timely, because
108 * the main loop might wait for an arbitrarily long time. If possible,
109 * you should instead create a separate thread that does a blocking poll
110 * and set a Win32 event object. The event can then be passed to
111 * qemu_add_wait_object.
112 *
113 * Polling callbacks really have nothing Windows specific in them, but
114 * as they are a hack and are currently not necessary under POSIX systems,
115 * they are only available when QEMU is running under Windows.
116 *
117 * @func: The function that does the polling, and returns 1 to force
118 * immediate completion of main_loop_wait.
119 * @opaque: A pointer-size value that is passed to @func.
120 */
121 int qemu_add_polling_cb(PollingFunc *func, void *opaque);
122
123 /**
124 * qemu_del_polling_cb: Unregister a Windows-specific polling callback
125 *
126 * This function removes a callback that was registered with
127 * qemu_add_polling_cb.
128 *
129 * @func: The function that was passed to qemu_add_polling_cb.
130 * @opaque: A pointer-size value that was passed to qemu_add_polling_cb.
131 */
132 void qemu_del_polling_cb(PollingFunc *func, void *opaque);
133
134 /* Wait objects handling */
135 typedef void WaitObjectFunc(void *opaque);
136
137 /**
138 * qemu_add_wait_object: Register a callback for a Windows handle
139 *
140 * Under Windows, the iohandler mechanism can only be used with sockets.
141 * QEMU must use the WaitForMultipleObjects API to wait on other handles.
142 * This function registers a #HANDLE with QEMU, so that it will be included
143 * in the main loop's calls to WaitForMultipleObjects. When the handle
144 * is in a signaled state, QEMU will call @func.
145 *
146 * @handle: The Windows handle to be observed.
147 * @func: A function to be called when @handle is in a signaled state.
148 * @opaque: A pointer-size value that is passed to @func.
149 */
150 int qemu_add_wait_object(HANDLE handle, WaitObjectFunc *func, void *opaque);
151
152 /**
153 * qemu_del_wait_object: Unregister a callback for a Windows handle
154 *
155 * This function removes a callback that was registered with
156 * qemu_add_wait_object.
157 *
158 * @func: The function that was passed to qemu_add_wait_object.
159 * @opaque: A pointer-size value that was passed to qemu_add_wait_object.
160 */
161 void qemu_del_wait_object(HANDLE handle, WaitObjectFunc *func, void *opaque);
162 #endif
163
164 /* async I/O support */
165
166 typedef void IOReadHandler(void *opaque, const uint8_t *buf, int size);
167 typedef int IOCanReadHandler(void *opaque);
168 typedef void IOHandler(void *opaque);
169
170 /**
171 * qemu_set_fd_handler2: Register a file descriptor with the main loop
172 *
173 * This function tells the main loop to wake up whenever one of the
174 * following conditions is true:
175 *
176 * 1) if @fd_write is not %NULL, when the file descriptor is writable;
177 *
178 * 2) if @fd_read is not %NULL, when the file descriptor is readable.
179 *
180 * @fd_read_poll can be used to disable the @fd_read callback temporarily.
181 * This is useful to avoid calling qemu_set_fd_handler2 every time the
182 * client becomes interested in reading (or dually, stops being interested).
183 * A typical example is when @fd is a listening socket and you want to bound
184 * the number of active clients. Remember to call qemu_notify_event whenever
185 * the condition may change from %false to %true.
186 *
187 * The callbacks that are set up by qemu_set_fd_handler2 are level-triggered.
188 * If @fd_read does not read from @fd, or @fd_write does not write to @fd
189 * until its buffers are full, they will be called again on the next
190 * iteration.
191 *
192 * @fd: The file descriptor to be observed. Under Windows it must be
193 * a #SOCKET.
194 *
195 * @fd_read_poll: A function that returns 1 if the @fd_read callback
196 * should be fired. If the function returns 0, the main loop will not
197 * end its iteration even if @fd becomes readable.
198 *
199 * @fd_read: A level-triggered callback that is fired if @fd is readable
200 * at the beginning of a main loop iteration, or if it becomes readable
201 * during one.
202 *
203 * @fd_write: A level-triggered callback that is fired when @fd is writable
204 * at the beginning of a main loop iteration, or if it becomes writable
205 * during one.
206 *
207 * @opaque: A pointer-sized value that is passed to @fd_read_poll,
208 * @fd_read and @fd_write.
209 */
210 int qemu_set_fd_handler2(int fd,
211 IOCanReadHandler *fd_read_poll,
212 IOHandler *fd_read,
213 IOHandler *fd_write,
214 void *opaque);
215
216 /**
217 * qemu_set_fd_handler: Register a file descriptor with the main loop
218 *
219 * This function tells the main loop to wake up whenever one of the
220 * following conditions is true:
221 *
222 * 1) if @fd_write is not %NULL, when the file descriptor is writable;
223 *
224 * 2) if @fd_read is not %NULL, when the file descriptor is readable.
225 *
226 * The callbacks that are set up by qemu_set_fd_handler are level-triggered.
227 * If @fd_read does not read from @fd, or @fd_write does not write to @fd
228 * until its buffers are full, they will be called again on the next
229 * iteration.
230 *
231 * @fd: The file descriptor to be observed. Under Windows it must be
232 * a #SOCKET.
233 *
234 * @fd_read: A level-triggered callback that is fired if @fd is readable
235 * at the beginning of a main loop iteration, or if it becomes readable
236 * during one.
237 *
238 * @fd_write: A level-triggered callback that is fired when @fd is writable
239 * at the beginning of a main loop iteration, or if it becomes writable
240 * during one.
241 *
242 * @opaque: A pointer-sized value that is passed to @fd_read and @fd_write.
243 */
244 int qemu_set_fd_handler(int fd,
245 IOHandler *fd_read,
246 IOHandler *fd_write,
247 void *opaque);
248
249 typedef struct QEMUBH QEMUBH;
250 typedef void QEMUBHFunc(void *opaque);
251
252 /**
253 * qemu_bh_new: Allocate a new bottom half structure.
254 *
255 * Bottom halves are lightweight callbacks whose invocation is guaranteed
256 * to be wait-free, thread-safe and signal-safe. The #QEMUBH structure
257 * is opaque and must be allocated prior to its use.
258 */
259 QEMUBH *qemu_bh_new(QEMUBHFunc *cb, void *opaque);
260
261 /**
262 * qemu_bh_schedule: Schedule a bottom half.
263 *
264 * Scheduling a bottom half interrupts the main loop and causes the
265 * execution of the callback that was passed to qemu_bh_new.
266 *
267 * Bottom halves that are scheduled from a bottom half handler are instantly
268 * invoked. This can create an infinite loop if a bottom half handler
269 * schedules itself.
270 *
271 * @bh: The bottom half to be scheduled.
272 */
273 void qemu_bh_schedule(QEMUBH *bh);
274
275 /**
276 * qemu_bh_cancel: Cancel execution of a bottom half.
277 *
278 * Canceling execution of a bottom half undoes the effect of calls to
279 * qemu_bh_schedule without freeing its resources yet. While cancellation
280 * itself is also wait-free and thread-safe, it can of course race with the
281 * loop that executes bottom halves unless you are holding the iothread
282 * mutex. This makes it mostly useless if you are not holding the mutex.
283 *
284 * @bh: The bottom half to be canceled.
285 */
286 void qemu_bh_cancel(QEMUBH *bh);
287
288 /**
289 *qemu_bh_delete: Cancel execution of a bottom half and free its resources.
290 *
291 * Deleting a bottom half frees the memory that was allocated for it by
292 * qemu_bh_new. It also implies canceling the bottom half if it was
293 * scheduled.
294 *
295 * @bh: The bottom half to be deleted.
296 */
297 void qemu_bh_delete(QEMUBH *bh);
298
299 #ifdef CONFIG_POSIX
300 /**
301 * qemu_add_child_watch: Register a child process for reaping.
302 *
303 * Under POSIX systems, a parent process must read the exit status of
304 * its child processes using waitpid, or the operating system will not
305 * free some of the resources attached to that process.
306 *
307 * This function directs the QEMU main loop to observe a child process
308 * and call waitpid as soon as it exits; the watch is then removed
309 * automatically. It is useful whenever QEMU forks a child process
310 * but will find out about its termination by other means such as a
311 * "broken pipe".
312 *
313 * @pid: The pid that QEMU should observe.
314 */
315 int qemu_add_child_watch(pid_t pid);
316 #endif
317
318 /**
319 * qemu_mutex_lock_iothread: Lock the main loop mutex.
320 *
321 * This function locks the main loop mutex. The mutex is taken by
322 * qemu_init_main_loop and always taken except while waiting on
323 * external events (such as with select). The mutex should be taken
324 * by threads other than the main loop thread when calling
325 * qemu_bh_new(), qemu_set_fd_handler() and basically all other
326 * functions documented in this file.
327 *
328 * NOTE: tools currently are single-threaded and qemu_mutex_lock_iothread
329 * is a no-op there.
330 */
331 void qemu_mutex_lock_iothread(void);
332
333 /**
334 * qemu_mutex_unlock_iothread: Unlock the main loop mutex.
335 *
336 * This function unlocks the main loop mutex. The mutex is taken by
337 * qemu_init_main_loop and always taken except while waiting on
338 * external events (such as with select). The mutex should be unlocked
339 * as soon as possible by threads other than the main loop thread,
340 * because it prevents the main loop from processing callbacks,
341 * including timers and bottom halves.
342 *
343 * NOTE: tools currently are single-threaded and qemu_mutex_unlock_iothread
344 * is a no-op there.
345 */
346 void qemu_mutex_unlock_iothread(void);
347
348 /* internal interfaces */
349
350 void qemu_iohandler_fill(int *pnfds, fd_set *readfds, fd_set *writefds, fd_set *xfds);
351 void qemu_iohandler_poll(fd_set *readfds, fd_set *writefds, fd_set *xfds, int rc);
352
353 void qemu_bh_schedule_idle(QEMUBH *bh);
354 int qemu_bh_poll(void);
355 void qemu_bh_update_timeout(int *timeout);
356
357 #endif