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 #include "qom/object.h" 30 #include "sysemu/event-loop-base.h" 31 32 #define SIG_IPI SIGUSR1 33 34 #define TYPE_MAIN_LOOP "main-loop" 35 OBJECT_DECLARE_TYPE(MainLoop, MainLoopClass, MAIN_LOOP) 36 37 struct MainLoop { 38 EventLoopBase parent_obj; 39 }; 40 typedef struct MainLoop MainLoop; 41 42 /** 43 * qemu_init_main_loop: Set up the process so that it can run the main loop. 44 * 45 * This includes setting up signal handlers. It should be called before 46 * any other threads are created. In addition, threads other than the 47 * main one should block signals that are trapped by the main loop. 48 * For simplicity, you can consider these signals to be safe: SIGUSR1, 49 * SIGUSR2, thread signals (SIGFPE, SIGILL, SIGSEGV, SIGBUS) and real-time 50 * signals if available. Remember that Windows in practice does not have 51 * signals, though. 52 * 53 * In the case of QEMU tools, this will also start/initialize timers. 54 */ 55 int qemu_init_main_loop(Error **errp); 56 57 /** 58 * main_loop_wait: Run one iteration of the main loop. 59 * 60 * If @nonblocking is true, poll for events, otherwise suspend until 61 * one actually occurs. The main loop usually consists of a loop that 62 * repeatedly calls main_loop_wait(false). 63 * 64 * Main loop services include file descriptor callbacks, bottom halves 65 * and timers (defined in qemu/timer.h). Bottom halves are similar to timers 66 * that execute immediately, but have a lower overhead and scheduling them 67 * is wait-free, thread-safe and signal-safe. 68 * 69 * It is sometimes useful to put a whole program in a coroutine. In this 70 * case, the coroutine actually should be started from within the main loop, 71 * so that the main loop can run whenever the coroutine yields. To do this, 72 * you can use a bottom half to enter the coroutine as soon as the main loop 73 * starts: 74 * 75 * void enter_co_bh(void *opaque) { 76 * QEMUCoroutine *co = opaque; 77 * qemu_coroutine_enter(co); 78 * } 79 * 80 * ... 81 * QEMUCoroutine *co = qemu_coroutine_create(coroutine_entry, NULL); 82 * QEMUBH *start_bh = qemu_bh_new(enter_co_bh, co); 83 * qemu_bh_schedule(start_bh); 84 * while (...) { 85 * main_loop_wait(false); 86 * } 87 * 88 * (In the future we may provide a wrapper for this). 89 * 90 * @nonblocking: Whether the caller should block until an event occurs. 91 */ 92 void main_loop_wait(int nonblocking); 93 94 /** 95 * qemu_get_aio_context: Return the main loop's AioContext 96 */ 97 AioContext *qemu_get_aio_context(void); 98 99 /** 100 * qemu_notify_event: Force processing of pending events. 101 * 102 * Similar to signaling a condition variable, qemu_notify_event forces 103 * main_loop_wait to look at pending events and exit. The caller of 104 * main_loop_wait will usually call it again very soon, so qemu_notify_event 105 * also has the side effect of recalculating the sets of file descriptors 106 * that the main loop waits for. 107 * 108 * Calling qemu_notify_event is rarely necessary, because main loop 109 * services (bottom halves and timers) call it themselves. 110 */ 111 void qemu_notify_event(void); 112 113 #ifdef _WIN32 114 /* return TRUE if no sleep should be done afterwards */ 115 typedef int PollingFunc(void *opaque); 116 117 /** 118 * qemu_add_polling_cb: Register a Windows-specific polling callback 119 * 120 * Currently, under Windows some events are polled rather than waited for. 121 * Polling callbacks do not ensure that @func is called timely, because 122 * the main loop might wait for an arbitrarily long time. If possible, 123 * you should instead create a separate thread that does a blocking poll 124 * and set a Win32 event object. The event can then be passed to 125 * qemu_add_wait_object. 126 * 127 * Polling callbacks really have nothing Windows specific in them, but 128 * as they are a hack and are currently not necessary under POSIX systems, 129 * they are only available when QEMU is running under Windows. 130 * 131 * @func: The function that does the polling, and returns 1 to force 132 * immediate completion of main_loop_wait. 133 * @opaque: A pointer-size value that is passed to @func. 134 */ 135 int qemu_add_polling_cb(PollingFunc *func, void *opaque); 136 137 /** 138 * qemu_del_polling_cb: Unregister a Windows-specific polling callback 139 * 140 * This function removes a callback that was registered with 141 * qemu_add_polling_cb. 142 * 143 * @func: The function that was passed to qemu_add_polling_cb. 144 * @opaque: A pointer-size value that was passed to qemu_add_polling_cb. 145 */ 146 void qemu_del_polling_cb(PollingFunc *func, void *opaque); 147 148 /* Wait objects handling */ 149 typedef void WaitObjectFunc(void *opaque); 150 151 /** 152 * qemu_add_wait_object: Register a callback for a Windows handle 153 * 154 * Under Windows, the iohandler mechanism can only be used with sockets. 155 * QEMU must use the WaitForMultipleObjects API to wait on other handles. 156 * This function registers a #HANDLE with QEMU, so that it will be included 157 * in the main loop's calls to WaitForMultipleObjects. When the handle 158 * is in a signaled state, QEMU will call @func. 159 * 160 * If the same HANDLE is added twice, this function returns -1. 161 * 162 * @handle: The Windows handle to be observed. 163 * @func: A function to be called when @handle is in a signaled state. 164 * @opaque: A pointer-size value that is passed to @func. 165 */ 166 int qemu_add_wait_object(HANDLE handle, WaitObjectFunc *func, void *opaque); 167 168 /** 169 * qemu_del_wait_object: Unregister a callback for a Windows handle 170 * 171 * This function removes a callback that was registered with 172 * qemu_add_wait_object. 173 * 174 * @func: The function that was passed to qemu_add_wait_object. 175 * @opaque: A pointer-size value that was passed to qemu_add_wait_object. 176 */ 177 void qemu_del_wait_object(HANDLE handle, WaitObjectFunc *func, void *opaque); 178 #endif 179 180 /* async I/O support */ 181 182 typedef void IOReadHandler(void *opaque, const uint8_t *buf, int size); 183 184 /** 185 * IOCanReadHandler: Return the number of bytes that #IOReadHandler can accept 186 * 187 * This function reports how many bytes #IOReadHandler is prepared to accept. 188 * #IOReadHandler may be invoked with up to this number of bytes. If this 189 * function returns 0 then #IOReadHandler is not invoked. 190 * 191 * This function is typically called from an event loop. If the number of 192 * bytes changes outside the event loop (e.g. because a vcpu thread drained the 193 * buffer), then it is necessary to kick the event loop so that this function 194 * is called again. aio_notify() or qemu_notify_event() can be used to kick 195 * the event loop. 196 */ 197 typedef int IOCanReadHandler(void *opaque); 198 199 /** 200 * qemu_set_fd_handler: Register a file descriptor with the main loop 201 * 202 * This function tells the main loop to wake up whenever one of the 203 * following conditions is true: 204 * 205 * 1) if @fd_write is not %NULL, when the file descriptor is writable; 206 * 207 * 2) if @fd_read is not %NULL, when the file descriptor is readable. 208 * 209 * The callbacks that are set up by qemu_set_fd_handler are level-triggered. 210 * If @fd_read does not read from @fd, or @fd_write does not write to @fd 211 * until its buffers are full, they will be called again on the next 212 * iteration. 213 * 214 * @fd: The file descriptor to be observed. Under Windows it must be 215 * a #SOCKET. 216 * 217 * @fd_read: A level-triggered callback that is fired if @fd is readable 218 * at the beginning of a main loop iteration, or if it becomes readable 219 * during one. 220 * 221 * @fd_write: A level-triggered callback that is fired when @fd is writable 222 * at the beginning of a main loop iteration, or if it becomes writable 223 * during one. 224 * 225 * @opaque: A pointer-sized value that is passed to @fd_read and @fd_write. 226 */ 227 void qemu_set_fd_handler(int fd, 228 IOHandler *fd_read, 229 IOHandler *fd_write, 230 void *opaque); 231 232 233 /** 234 * event_notifier_set_handler: Register an EventNotifier with the main loop 235 * 236 * This function tells the main loop to wake up whenever the 237 * #EventNotifier was set. 238 * 239 * @e: The #EventNotifier to be observed. 240 * 241 * @handler: A level-triggered callback that is fired when @e 242 * has been set. @e is passed to it as a parameter. 243 */ 244 void event_notifier_set_handler(EventNotifier *e, 245 EventNotifierHandler *handler); 246 247 GSource *iohandler_get_g_source(void); 248 AioContext *iohandler_get_aio_context(void); 249 250 /** 251 * bql_locked: Return lock status of the Big QEMU Lock (BQL) 252 * 253 * The Big QEMU Lock (BQL) is the coarsest lock in QEMU, and as such it 254 * must always be taken outside other locks. This function helps 255 * functions take different paths depending on whether the current 256 * thread is running within the BQL. 257 * 258 * This function should never be used in the block layer, because 259 * unit tests, block layer tools and qemu-storage-daemon do not 260 * have a BQL. 261 * Please instead refer to qemu_in_main_thread(). 262 */ 263 bool bql_locked(void); 264 265 /** 266 * qemu_in_main_thread: return whether it's possible to safely access 267 * the global state of the block layer. 268 * 269 * Global state of the block layer is not accessible from I/O threads 270 * or worker threads; only from threads that "own" the default 271 * AioContext that qemu_get_aio_context() returns. For tests, block 272 * layer tools and qemu-storage-daemon there is a designated thread that 273 * runs the event loop for qemu_get_aio_context(), and that is the 274 * main thread. 275 * 276 * For emulators, however, any thread that holds the BQL can act 277 * as the block layer main thread; this will be any of the actual 278 * main thread, the vCPU threads or the RCU thread. 279 * 280 * For clarity, do not use this function outside the block layer. 281 */ 282 bool qemu_in_main_thread(void); 283 284 /* 285 * Mark and check that the function is part of the Global State API. 286 * Please refer to include/block/block-global-state.h for more 287 * information about GS API. 288 */ 289 #define GLOBAL_STATE_CODE() \ 290 do { \ 291 assert(qemu_in_main_thread()); \ 292 } while (0) 293 294 /* 295 * Mark and check that the function is part of the I/O API. 296 * Please refer to include/block/block-io.h for more 297 * information about IO API. 298 */ 299 #define IO_CODE() \ 300 do { \ 301 /* nop */ \ 302 } while (0) 303 304 /* 305 * Mark and check that the function is part of the "I/O OR GS" API. 306 * Please refer to include/block/block-io.h for more 307 * information about "IO or GS" API. 308 */ 309 #define IO_OR_GS_CODE() \ 310 do { \ 311 /* nop */ \ 312 } while (0) 313 314 /** 315 * bql_lock: Lock the Big QEMU Lock (BQL). 316 * 317 * This function locks the Big QEMU Lock (BQL). The lock is taken by 318 * main() in vl.c and always taken except while waiting on 319 * external events (such as with select). The lock should be taken 320 * by threads other than the main loop thread when calling 321 * qemu_bh_new(), qemu_set_fd_handler() and basically all other 322 * functions documented in this file. 323 * 324 * NOTE: tools currently are single-threaded and bql_lock 325 * is a no-op there. 326 */ 327 #define bql_lock() bql_lock_impl(__FILE__, __LINE__) 328 void bql_lock_impl(const char *file, int line); 329 330 /** 331 * bql_unlock: Unlock the Big QEMU Lock (BQL). 332 * 333 * This function unlocks the Big QEMU Lock. The lock is taken by 334 * main() in vl.c and always taken except while waiting on 335 * external events (such as with select). The lock 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 * NOTE: tools currently are single-threaded and bql_unlock 341 * is a no-op there. 342 */ 343 void bql_unlock(void); 344 345 /** 346 * BQL_LOCK_GUARD 347 * 348 * Wrap a block of code in a conditional bql_{lock,unlock}. 349 */ 350 typedef struct BQLLockAuto BQLLockAuto; 351 352 static inline BQLLockAuto *bql_auto_lock(const char *file, int line) 353 { 354 if (bql_locked()) { 355 return NULL; 356 } 357 bql_lock_impl(file, line); 358 /* Anything non-NULL causes the cleanup function to be called */ 359 return (BQLLockAuto *)(uintptr_t)1; 360 } 361 362 static inline void bql_auto_unlock(BQLLockAuto *l) 363 { 364 bql_unlock(); 365 } 366 367 G_DEFINE_AUTOPTR_CLEANUP_FUNC(BQLLockAuto, bql_auto_unlock) 368 369 #define BQL_LOCK_GUARD() \ 370 g_autoptr(BQLLockAuto) _bql_lock_auto __attribute__((unused)) \ 371 = bql_auto_lock(__FILE__, __LINE__) 372 373 /* 374 * qemu_cond_wait_bql: Wait on condition for the Big QEMU Lock (BQL) 375 * 376 * This function atomically releases the Big QEMU Lock (BQL) and causes 377 * the calling thread to block on the condition. 378 */ 379 void qemu_cond_wait_bql(QemuCond *cond); 380 381 /* 382 * qemu_cond_timedwait_bql: like the previous, but with timeout 383 */ 384 void qemu_cond_timedwait_bql(QemuCond *cond, int ms); 385 386 /* internal interfaces */ 387 388 #define qemu_bh_new_guarded(cb, opaque, guard) \ 389 qemu_bh_new_full((cb), (opaque), (stringify(cb)), guard) 390 #define qemu_bh_new(cb, opaque) \ 391 qemu_bh_new_full((cb), (opaque), (stringify(cb)), NULL) 392 QEMUBH *qemu_bh_new_full(QEMUBHFunc *cb, void *opaque, const char *name, 393 MemReentrancyGuard *reentrancy_guard); 394 void qemu_bh_schedule_idle(QEMUBH *bh); 395 396 enum { 397 MAIN_LOOP_POLL_FILL, 398 MAIN_LOOP_POLL_ERR, 399 MAIN_LOOP_POLL_OK, 400 }; 401 402 typedef struct MainLoopPoll { 403 int state; 404 uint32_t timeout; 405 GArray *pollfds; 406 } MainLoopPoll; 407 408 void main_loop_poll_add_notifier(Notifier *notify); 409 void main_loop_poll_remove_notifier(Notifier *notify); 410 411 #endif 412