Paolo Bonzini | 44a9b35 | 2011-09-12 16:44:30 +0200 | [diff] [blame] | 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 currenly 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 | |
Paolo Bonzini | d3b12f5 | 2011-09-13 10:30:52 +0200 | [diff] [blame] | 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 | void qemu_mutex_lock_iothread(void); |
| 329 | |
| 330 | /** |
| 331 | * qemu_mutex_unlock_iothread: Unlock the main loop mutex. |
| 332 | * |
| 333 | * This function unlocks the main loop mutex. The mutex is taken by |
| 334 | * qemu_init_main_loop and always taken except while waiting on |
| 335 | * external events (such as with select). The mutex should be unlocked |
| 336 | * as soon as possible by threads other than the main loop thread, |
| 337 | * because it prevents the main loop from processing callbacks, |
| 338 | * including timers and bottom halves. |
| 339 | */ |
| 340 | void qemu_mutex_unlock_iothread(void); |
| 341 | |
Paolo Bonzini | 44a9b35 | 2011-09-12 16:44:30 +0200 | [diff] [blame] | 342 | /* internal interfaces */ |
| 343 | |
| 344 | void qemu_iohandler_fill(int *pnfds, fd_set *readfds, fd_set *writefds, fd_set *xfds); |
| 345 | void qemu_iohandler_poll(fd_set *readfds, fd_set *writefds, fd_set *xfds, int rc); |
| 346 | |
| 347 | void qemu_bh_schedule_idle(QEMUBH *bh); |
| 348 | int qemu_bh_poll(void); |
| 349 | void qemu_bh_update_timeout(int *timeout); |
| 350 | |
| 351 | #endif |