Annotation of qemu/main-loop.h, revision 1.1.1.2

1.1       root        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: #define SIG_IPI SIGUSR1
                     29: 
                     30: /**
                     31:  * qemu_init_main_loop: Set up the process so that it can run the main loop.
                     32:  *
                     33:  * This includes setting up signal handlers.  It should be called before
                     34:  * any other threads are created.  In addition, threads other than the
                     35:  * main one should block signals that are trapped by the main loop.
                     36:  * For simplicity, you can consider these signals to be safe: SIGUSR1,
                     37:  * SIGUSR2, thread signals (SIGFPE, SIGILL, SIGSEGV, SIGBUS) and real-time
                     38:  * signals if available.  Remember that Windows in practice does not have
                     39:  * signals, though.
1.1.1.2 ! root       40:  *
        !            41:  * In the case of QEMU tools, this will also start/initialize timers.
1.1       root       42:  */
                     43: int qemu_init_main_loop(void);
                     44: 
                     45: /**
1.1.1.2 ! root       46:  * main_loop_init: Initializes main loop
        !            47:  *
        !            48:  * Internal (but shared for compatibility reasons) initialization routine
        !            49:  * for the main loop. This should not be used by applications directly,
        !            50:  * use qemu_init_main_loop() instead.
        !            51:  *
        !            52:  */
        !            53: int main_loop_init(void);
        !            54: 
        !            55: /**
1.1       root       56:  * main_loop_wait: Run one iteration of the main loop.
                     57:  *
                     58:  * If @nonblocking is true, poll for events, otherwise suspend until
                     59:  * one actually occurs.  The main loop usually consists of a loop that
                     60:  * repeatedly calls main_loop_wait(false).
                     61:  *
                     62:  * Main loop services include file descriptor callbacks, bottom halves
                     63:  * and timers (defined in qemu-timer.h).  Bottom halves are similar to timers
                     64:  * that execute immediately, but have a lower overhead and scheduling them
                     65:  * is wait-free, thread-safe and signal-safe.
                     66:  *
                     67:  * It is sometimes useful to put a whole program in a coroutine.  In this
                     68:  * case, the coroutine actually should be started from within the main loop,
                     69:  * so that the main loop can run whenever the coroutine yields.  To do this,
                     70:  * you can use a bottom half to enter the coroutine as soon as the main loop
                     71:  * starts:
                     72:  *
                     73:  *     void enter_co_bh(void *opaque) {
                     74:  *         QEMUCoroutine *co = opaque;
                     75:  *         qemu_coroutine_enter(co, NULL);
                     76:  *     }
                     77:  *
                     78:  *     ...
                     79:  *     QEMUCoroutine *co = qemu_coroutine_create(coroutine_entry);
                     80:  *     QEMUBH *start_bh = qemu_bh_new(enter_co_bh, co);
                     81:  *     qemu_bh_schedule(start_bh);
                     82:  *     while (...) {
                     83:  *         main_loop_wait(false);
                     84:  *     }
                     85:  *
                     86:  * (In the future we may provide a wrapper for this).
                     87:  *
                     88:  * @nonblocking: Whether the caller should block until an event occurs.
                     89:  */
                     90: int main_loop_wait(int nonblocking);
                     91: 
                     92: /**
                     93:  * qemu_notify_event: Force processing of pending events.
                     94:  *
                     95:  * Similar to signaling a condition variable, qemu_notify_event forces
                     96:  * main_loop_wait to look at pending events and exit.  The caller of
                     97:  * main_loop_wait will usually call it again very soon, so qemu_notify_event
                     98:  * also has the side effect of recalculating the sets of file descriptors
                     99:  * that the main loop waits for.
                    100:  *
                    101:  * Calling qemu_notify_event is rarely necessary, because main loop
                    102:  * services (bottom halves and timers) call it themselves.  One notable
                    103:  * exception occurs when using qemu_set_fd_handler2 (see below).
                    104:  */
                    105: void qemu_notify_event(void);
                    106: 
                    107: #ifdef _WIN32
                    108: /* return TRUE if no sleep should be done afterwards */
                    109: typedef int PollingFunc(void *opaque);
                    110: 
                    111: /**
                    112:  * qemu_add_polling_cb: Register a Windows-specific polling callback
                    113:  *
                    114:  * Currently, under Windows some events are polled rather than waited for.
                    115:  * Polling callbacks do not ensure that @func is called timely, because
                    116:  * the main loop might wait for an arbitrarily long time.  If possible,
                    117:  * you should instead create a separate thread that does a blocking poll
                    118:  * and set a Win32 event object.  The event can then be passed to
                    119:  * qemu_add_wait_object.
                    120:  *
                    121:  * Polling callbacks really have nothing Windows specific in them, but
1.1.1.2 ! root      122:  * as they are a hack and are currently not necessary under POSIX systems,
1.1       root      123:  * they are only available when QEMU is running under Windows.
                    124:  *
                    125:  * @func: The function that does the polling, and returns 1 to force
                    126:  * immediate completion of main_loop_wait.
                    127:  * @opaque: A pointer-size value that is passed to @func.
                    128:  */
                    129: int qemu_add_polling_cb(PollingFunc *func, void *opaque);
                    130: 
                    131: /**
                    132:  * qemu_del_polling_cb: Unregister a Windows-specific polling callback
                    133:  *
                    134:  * This function removes a callback that was registered with
                    135:  * qemu_add_polling_cb.
                    136:  *
                    137:  * @func: The function that was passed to qemu_add_polling_cb.
                    138:  * @opaque: A pointer-size value that was passed to qemu_add_polling_cb.
                    139:  */
                    140: void qemu_del_polling_cb(PollingFunc *func, void *opaque);
                    141: 
                    142: /* Wait objects handling */
                    143: typedef void WaitObjectFunc(void *opaque);
                    144: 
                    145: /**
                    146:  * qemu_add_wait_object: Register a callback for a Windows handle
                    147:  *
                    148:  * Under Windows, the iohandler mechanism can only be used with sockets.
                    149:  * QEMU must use the WaitForMultipleObjects API to wait on other handles.
                    150:  * This function registers a #HANDLE with QEMU, so that it will be included
                    151:  * in the main loop's calls to WaitForMultipleObjects.  When the handle
                    152:  * is in a signaled state, QEMU will call @func.
                    153:  *
                    154:  * @handle: The Windows handle to be observed.
                    155:  * @func: A function to be called when @handle is in a signaled state.
                    156:  * @opaque: A pointer-size value that is passed to @func.
                    157:  */
                    158: int qemu_add_wait_object(HANDLE handle, WaitObjectFunc *func, void *opaque);
                    159: 
                    160: /**
                    161:  * qemu_del_wait_object: Unregister a callback for a Windows handle
                    162:  *
                    163:  * This function removes a callback that was registered with
                    164:  * qemu_add_wait_object.
                    165:  *
                    166:  * @func: The function that was passed to qemu_add_wait_object.
                    167:  * @opaque: A pointer-size value that was passed to qemu_add_wait_object.
                    168:  */
                    169: void qemu_del_wait_object(HANDLE handle, WaitObjectFunc *func, void *opaque);
                    170: #endif
                    171: 
                    172: /* async I/O support */
                    173: 
                    174: typedef void IOReadHandler(void *opaque, const uint8_t *buf, int size);
                    175: typedef int IOCanReadHandler(void *opaque);
                    176: typedef void IOHandler(void *opaque);
                    177: 
                    178: /**
                    179:  * qemu_set_fd_handler2: Register a file descriptor with the main loop
                    180:  *
                    181:  * This function tells the main loop to wake up whenever one of the
                    182:  * following conditions is true:
                    183:  *
                    184:  * 1) if @fd_write is not %NULL, when the file descriptor is writable;
                    185:  *
                    186:  * 2) if @fd_read is not %NULL, when the file descriptor is readable.
                    187:  *
                    188:  * @fd_read_poll can be used to disable the @fd_read callback temporarily.
                    189:  * This is useful to avoid calling qemu_set_fd_handler2 every time the
                    190:  * client becomes interested in reading (or dually, stops being interested).
                    191:  * A typical example is when @fd is a listening socket and you want to bound
                    192:  * the number of active clients.  Remember to call qemu_notify_event whenever
                    193:  * the condition may change from %false to %true.
                    194:  *
                    195:  * The callbacks that are set up by qemu_set_fd_handler2 are level-triggered.
                    196:  * If @fd_read does not read from @fd, or @fd_write does not write to @fd
                    197:  * until its buffers are full, they will be called again on the next
                    198:  * iteration.
                    199:  *
                    200:  * @fd: The file descriptor to be observed.  Under Windows it must be
                    201:  * a #SOCKET.
                    202:  *
                    203:  * @fd_read_poll: A function that returns 1 if the @fd_read callback
                    204:  * should be fired.  If the function returns 0, the main loop will not
                    205:  * end its iteration even if @fd becomes readable.
                    206:  *
                    207:  * @fd_read: A level-triggered callback that is fired if @fd is readable
                    208:  * at the beginning of a main loop iteration, or if it becomes readable
                    209:  * during one.
                    210:  *
                    211:  * @fd_write: A level-triggered callback that is fired when @fd is writable
                    212:  * at the beginning of a main loop iteration, or if it becomes writable
                    213:  * during one.
                    214:  *
                    215:  * @opaque: A pointer-sized value that is passed to @fd_read_poll,
                    216:  * @fd_read and @fd_write.
                    217:  */
                    218: int qemu_set_fd_handler2(int fd,
                    219:                          IOCanReadHandler *fd_read_poll,
                    220:                          IOHandler *fd_read,
                    221:                          IOHandler *fd_write,
                    222:                          void *opaque);
                    223: 
                    224: /**
                    225:  * qemu_set_fd_handler: Register a file descriptor with the main loop
                    226:  *
                    227:  * This function tells the main loop to wake up whenever one of the
                    228:  * following conditions is true:
                    229:  *
                    230:  * 1) if @fd_write is not %NULL, when the file descriptor is writable;
                    231:  *
                    232:  * 2) if @fd_read is not %NULL, when the file descriptor is readable.
                    233:  *
                    234:  * The callbacks that are set up by qemu_set_fd_handler are level-triggered.
                    235:  * If @fd_read does not read from @fd, or @fd_write does not write to @fd
                    236:  * until its buffers are full, they will be called again on the next
                    237:  * iteration.
                    238:  *
                    239:  * @fd: The file descriptor to be observed.  Under Windows it must be
                    240:  * a #SOCKET.
                    241:  *
                    242:  * @fd_read: A level-triggered callback that is fired if @fd is readable
                    243:  * at the beginning of a main loop iteration, or if it becomes readable
                    244:  * during one.
                    245:  *
                    246:  * @fd_write: A level-triggered callback that is fired when @fd is writable
                    247:  * at the beginning of a main loop iteration, or if it becomes writable
                    248:  * during one.
                    249:  *
                    250:  * @opaque: A pointer-sized value that is passed to @fd_read and @fd_write.
                    251:  */
                    252: int qemu_set_fd_handler(int fd,
                    253:                         IOHandler *fd_read,
                    254:                         IOHandler *fd_write,
                    255:                         void *opaque);
                    256: 
                    257: typedef struct QEMUBH QEMUBH;
                    258: typedef void QEMUBHFunc(void *opaque);
                    259: 
                    260: /**
                    261:  * qemu_bh_new: Allocate a new bottom half structure.
                    262:  *
                    263:  * Bottom halves are lightweight callbacks whose invocation is guaranteed
                    264:  * to be wait-free, thread-safe and signal-safe.  The #QEMUBH structure
                    265:  * is opaque and must be allocated prior to its use.
                    266:  */
                    267: QEMUBH *qemu_bh_new(QEMUBHFunc *cb, void *opaque);
                    268: 
                    269: /**
                    270:  * qemu_bh_schedule: Schedule a bottom half.
                    271:  *
                    272:  * Scheduling a bottom half interrupts the main loop and causes the
                    273:  * execution of the callback that was passed to qemu_bh_new.
                    274:  *
                    275:  * Bottom halves that are scheduled from a bottom half handler are instantly
                    276:  * invoked.  This can create an infinite loop if a bottom half handler
                    277:  * schedules itself.
                    278:  *
                    279:  * @bh: The bottom half to be scheduled.
                    280:  */
                    281: void qemu_bh_schedule(QEMUBH *bh);
                    282: 
                    283: /**
                    284:  * qemu_bh_cancel: Cancel execution of a bottom half.
                    285:  *
                    286:  * Canceling execution of a bottom half undoes the effect of calls to
                    287:  * qemu_bh_schedule without freeing its resources yet.  While cancellation
                    288:  * itself is also wait-free and thread-safe, it can of course race with the
                    289:  * loop that executes bottom halves unless you are holding the iothread
                    290:  * mutex.  This makes it mostly useless if you are not holding the mutex.
                    291:  *
                    292:  * @bh: The bottom half to be canceled.
                    293:  */
                    294: void qemu_bh_cancel(QEMUBH *bh);
                    295: 
                    296: /**
                    297:  *qemu_bh_delete: Cancel execution of a bottom half and free its resources.
                    298:  *
                    299:  * Deleting a bottom half frees the memory that was allocated for it by
                    300:  * qemu_bh_new.  It also implies canceling the bottom half if it was
                    301:  * scheduled.
                    302:  *
                    303:  * @bh: The bottom half to be deleted.
                    304:  */
                    305: void qemu_bh_delete(QEMUBH *bh);
                    306: 
                    307: #ifdef CONFIG_POSIX
                    308: /**
                    309:  * qemu_add_child_watch: Register a child process for reaping.
                    310:  *
                    311:  * Under POSIX systems, a parent process must read the exit status of
                    312:  * its child processes using waitpid, or the operating system will not
                    313:  * free some of the resources attached to that process.
                    314:  *
                    315:  * This function directs the QEMU main loop to observe a child process
                    316:  * and call waitpid as soon as it exits; the watch is then removed
                    317:  * automatically.  It is useful whenever QEMU forks a child process
                    318:  * but will find out about its termination by other means such as a
                    319:  * "broken pipe".
                    320:  *
                    321:  * @pid: The pid that QEMU should observe.
                    322:  */
                    323: int qemu_add_child_watch(pid_t pid);
                    324: #endif
                    325: 
                    326: /**
                    327:  * qemu_mutex_lock_iothread: Lock the main loop mutex.
                    328:  *
                    329:  * This function locks the main loop mutex.  The mutex is taken by
                    330:  * qemu_init_main_loop and always taken except while waiting on
                    331:  * external events (such as with select).  The mutex should be taken
                    332:  * by threads other than the main loop thread when calling
                    333:  * qemu_bh_new(), qemu_set_fd_handler() and basically all other
                    334:  * functions documented in this file.
1.1.1.2 ! root      335:  *
        !           336:  * NOTE: tools currently are single-threaded and qemu_mutex_lock_iothread
        !           337:  * is a no-op there.
1.1       root      338:  */
                    339: void qemu_mutex_lock_iothread(void);
                    340: 
                    341: /**
                    342:  * qemu_mutex_unlock_iothread: Unlock the main loop mutex.
                    343:  *
                    344:  * This function unlocks the main loop mutex.  The mutex is taken by
                    345:  * qemu_init_main_loop and always taken except while waiting on
                    346:  * external events (such as with select).  The mutex should be unlocked
                    347:  * as soon as possible by threads other than the main loop thread,
                    348:  * because it prevents the main loop from processing callbacks,
                    349:  * including timers and bottom halves.
1.1.1.2 ! root      350:  *
        !           351:  * NOTE: tools currently are single-threaded and qemu_mutex_unlock_iothread
        !           352:  * is a no-op there.
1.1       root      353:  */
                    354: void qemu_mutex_unlock_iothread(void);
                    355: 
                    356: /* internal interfaces */
                    357: 
1.1.1.2 ! root      358: void qemu_fd_register(int fd);
1.1       root      359: void qemu_iohandler_fill(int *pnfds, fd_set *readfds, fd_set *writefds, fd_set *xfds);
                    360: void qemu_iohandler_poll(fd_set *readfds, fd_set *writefds, fd_set *xfds, int rc);
                    361: 
                    362: void qemu_bh_schedule_idle(QEMUBH *bh);
                    363: int qemu_bh_poll(void);
1.1.1.2 ! root      364: void qemu_bh_update_timeout(uint32_t *timeout);
1.1       root      365: 
                    366: #endif

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