File:  [Qemu by Fabrice Bellard] / qemu / main-loop.h
Revision 1.1.1.1 (vendor branch): download - view: text, annotated - select for diffs
Tue Apr 24 19:16:32 2018 UTC (3 years, 1 month ago) by root
Branches: qemu, MAIN
CVS tags: qemu1001, HEAD
qemu 1.0.1

    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: 
  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: 
  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

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