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 #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 */ 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); 168 169 /** 170 * qemu_set_fd_handler2: Register a file descriptor with the main loop 171 * 172 * This function tells the main loop to wake up whenever one of the 173 * following conditions is true: 174 * 175 * 1) if @fd_write is not %NULL, when the file descriptor is writable; 176 * 177 * 2) if @fd_read is not %NULL, when the file descriptor is readable. 178 * 179 * @fd_read_poll can be used to disable the @fd_read callback temporarily. 180 * This is useful to avoid calling qemu_set_fd_handler2 every time the 181 * client becomes interested in reading (or dually, stops being interested). 182 * A typical example is when @fd is a listening socket and you want to bound 183 * the number of active clients. Remember to call qemu_notify_event whenever 184 * the condition may change from %false to %true. 185 * 186 * The callbacks that are set up by qemu_set_fd_handler2 are level-triggered. 187 * If @fd_read does not read from @fd, or @fd_write does not write to @fd 188 * until its buffers are full, they will be called again on the next 189 * iteration. 190 * 191 * @fd: The file descriptor to be observed. Under Windows it must be 192 * a #SOCKET. 193 * 194 * @fd_read_poll: A function that returns 1 if the @fd_read callback 195 * should be fired. If the function returns 0, the main loop will not 196 * end its iteration even if @fd becomes readable. 197 * 198 * @fd_read: A level-triggered callback that is fired if @fd is readable 199 * at the beginning of a main loop iteration, or if it becomes readable 200 * during one. 201 * 202 * @fd_write: A level-triggered callback that is fired when @fd is writable 203 * at the beginning of a main loop iteration, or if it becomes writable 204 * during one. 205 * 206 * @opaque: A pointer-sized value that is passed to @fd_read_poll, 207 * @fd_read and @fd_write. 208 */ 209 int qemu_set_fd_handler2(int fd, 210 IOCanReadHandler *fd_read_poll, 211 IOHandler *fd_read, 212 IOHandler *fd_write, 213 void *opaque); 214 215 /** 216 * qemu_set_fd_handler: Register a file descriptor with the main loop 217 * 218 * This function tells the main loop to wake up whenever one of the 219 * following conditions is true: 220 * 221 * 1) if @fd_write is not %NULL, when the file descriptor is writable; 222 * 223 * 2) if @fd_read is not %NULL, when the file descriptor is readable. 224 * 225 * The callbacks that are set up by qemu_set_fd_handler are level-triggered. 226 * If @fd_read does not read from @fd, or @fd_write does not write to @fd 227 * until its buffers are full, they will be called again on the next 228 * iteration. 229 * 230 * @fd: The file descriptor to be observed. Under Windows it must be 231 * a #SOCKET. 232 * 233 * @fd_read: A level-triggered callback that is fired if @fd is readable 234 * at the beginning of a main loop iteration, or if it becomes readable 235 * during one. 236 * 237 * @fd_write: A level-triggered callback that is fired when @fd is writable 238 * at the beginning of a main loop iteration, or if it becomes writable 239 * during one. 240 * 241 * @opaque: A pointer-sized value that is passed to @fd_read and @fd_write. 242 */ 243 int qemu_set_fd_handler(int fd, 244 IOHandler *fd_read, 245 IOHandler *fd_write, 246 void *opaque); 247 248 #ifdef CONFIG_POSIX 249 /** 250 * qemu_add_child_watch: Register a child process for reaping. 251 * 252 * Under POSIX systems, a parent process must read the exit status of 253 * its child processes using waitpid, or the operating system will not 254 * free some of the resources attached to that process. 255 * 256 * This function directs the QEMU main loop to observe a child process 257 * and call waitpid as soon as it exits; the watch is then removed 258 * automatically. It is useful whenever QEMU forks a child process 259 * but will find out about its termination by other means such as a 260 * "broken pipe". 261 * 262 * @pid: The pid that QEMU should observe. 263 */ 264 int qemu_add_child_watch(pid_t pid); 265 #endif 266 267 /** 268 * qemu_mutex_lock_iothread: Lock the main loop mutex. 269 * 270 * This function locks the main loop mutex. The mutex is taken by 271 * qemu_init_main_loop and always taken except while waiting on 272 * external events (such as with select). The mutex should be taken 273 * by threads other than the main loop thread when calling 274 * qemu_bh_new(), qemu_set_fd_handler() and basically all other 275 * functions documented in this file. 276 * 277 * NOTE: tools currently are single-threaded and qemu_mutex_lock_iothread 278 * is a no-op there. 279 */ 280 void qemu_mutex_lock_iothread(void); 281 282 /** 283 * qemu_mutex_unlock_iothread: Unlock the main loop mutex. 284 * 285 * This function unlocks 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 unlocked 288 * as soon as possible by threads other than the main loop thread, 289 * because it prevents the main loop from processing callbacks, 290 * including timers and bottom halves. 291 * 292 * NOTE: tools currently are single-threaded and qemu_mutex_unlock_iothread 293 * is a no-op there. 294 */ 295 void qemu_mutex_unlock_iothread(void); 296 297 /* internal interfaces */ 298 299 void qemu_fd_register(int fd); 300 void qemu_iohandler_fill(GArray *pollfds); 301 void qemu_iohandler_poll(GArray *pollfds, int rc); 302 303 QEMUBH *qemu_bh_new(QEMUBHFunc *cb, void *opaque); 304 void qemu_bh_schedule_idle(QEMUBH *bh); 305 306 #endif 307