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4 * Copyright (c) 2003-2008 Fabrice Bellard
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25 #ifndef QEMU_MAIN_LOOP_H
26 #define QEMU_MAIN_LOOP_H
28 #include "block/aio.h"
29 #include "qom/object.h"
30 #include "sysemu/event-loop-base.h"
32 #define SIG_IPI SIGUSR1
34 #define TYPE_MAIN_LOOP "main-loop"
35 OBJECT_DECLARE_TYPE(MainLoop
, MainLoopClass
, MAIN_LOOP
)
38 EventLoopBase parent_obj
;
40 typedef struct MainLoop MainLoop
;
43 * qemu_init_main_loop: Set up the process so that it can run the main loop.
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
53 * In the case of QEMU tools, this will also start/initialize timers.
55 int qemu_init_main_loop(Error
**errp
);
58 * main_loop_wait: Run one iteration of the main loop.
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).
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.
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
75 * void enter_co_bh(void *opaque) {
76 * QEMUCoroutine *co = opaque;
77 * qemu_coroutine_enter(co);
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);
85 * main_loop_wait(false);
88 * (In the future we may provide a wrapper for this).
90 * @nonblocking: Whether the caller should block until an event occurs.
92 void main_loop_wait(int nonblocking
);
95 * qemu_get_aio_context: Return the main loop's AioContext
97 AioContext
*qemu_get_aio_context(void);
100 * qemu_notify_event: Force processing of pending events.
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.
108 * Calling qemu_notify_event is rarely necessary, because main loop
109 * services (bottom halves and timers) call it themselves.
111 void qemu_notify_event(void);
114 /* return TRUE if no sleep should be done afterwards */
115 typedef int PollingFunc(void *opaque
);
118 * qemu_add_polling_cb: Register a Windows-specific polling callback
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.
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.
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.
135 int qemu_add_polling_cb(PollingFunc
*func
, void *opaque
);
138 * qemu_del_polling_cb: Unregister a Windows-specific polling callback
140 * This function removes a callback that was registered with
141 * qemu_add_polling_cb.
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.
146 void qemu_del_polling_cb(PollingFunc
*func
, void *opaque
);
148 /* Wait objects handling */
149 typedef void WaitObjectFunc(void *opaque
);
152 * qemu_add_wait_object: Register a callback for a Windows handle
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.
160 * If the same HANDLE is added twice, this function returns -1.
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.
166 int qemu_add_wait_object(HANDLE handle
, WaitObjectFunc
*func
, void *opaque
);
169 * qemu_del_wait_object: Unregister a callback for a Windows handle
171 * This function removes a callback that was registered with
172 * qemu_add_wait_object.
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.
177 void qemu_del_wait_object(HANDLE handle
, WaitObjectFunc
*func
, void *opaque
);
180 /* async I/O support */
182 typedef void IOReadHandler(void *opaque
, const uint8_t *buf
, int size
);
185 * IOCanReadHandler: Return the number of bytes that #IOReadHandler can accept
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.
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
197 typedef int IOCanReadHandler(void *opaque
);
200 * qemu_set_fd_handler: Register a file descriptor with the main loop
202 * This function tells the main loop to wake up whenever one of the
203 * following conditions is true:
205 * 1) if @fd_write is not %NULL, when the file descriptor is writable;
207 * 2) if @fd_read is not %NULL, when the file descriptor is readable.
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
214 * @fd: The file descriptor to be observed. Under Windows it must be
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
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
225 * @opaque: A pointer-sized value that is passed to @fd_read and @fd_write.
227 void qemu_set_fd_handler(int fd
,
234 * event_notifier_set_handler: Register an EventNotifier with the main loop
236 * This function tells the main loop to wake up whenever the
237 * #EventNotifier was set.
239 * @e: The #EventNotifier to be observed.
241 * @handler: A level-triggered callback that is fired when @e
242 * has been set. @e is passed to it as a parameter.
244 void event_notifier_set_handler(EventNotifier
*e
,
245 EventNotifierHandler
*handler
);
247 GSource
*iohandler_get_g_source(void);
248 AioContext
*iohandler_get_aio_context(void);
251 * qemu_mutex_iothread_locked: Return lock status of the main loop mutex.
253 * The main loop mutex 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 main loop mutex.
258 * This function should never be used in the block layer, because
259 * unit tests, block layer tools and qemu-storage-daemon do not
261 * Please instead refer to qemu_in_main_thread().
263 bool qemu_mutex_iothread_locked(void);
266 * qemu_in_main_thread: return whether it's possible to safely access
267 * the global state of the block layer.
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
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.
280 * For clarity, do not use this function outside the block layer.
282 bool qemu_in_main_thread(void);
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.
289 #define GLOBAL_STATE_CODE() \
291 assert(qemu_in_main_thread()); \
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.
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.
309 #define IO_OR_GS_CODE() \
315 * qemu_mutex_lock_iothread: Lock the main loop mutex.
317 * This function locks the main loop mutex. The mutex is taken by
318 * main() in vl.c and always taken except while waiting on
319 * external events (such as with select). The mutex 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.
324 * NOTE: tools currently are single-threaded and qemu_mutex_lock_iothread
327 #define qemu_mutex_lock_iothread() \
328 qemu_mutex_lock_iothread_impl(__FILE__, __LINE__)
329 void qemu_mutex_lock_iothread_impl(const char *file
, int line
);
332 * qemu_mutex_unlock_iothread: Unlock the main loop mutex.
334 * This function unlocks the main loop mutex. The mutex is taken by
335 * main() in vl.c and always taken except while waiting on
336 * external events (such as with select). The mutex should be unlocked
337 * as soon as possible by threads other than the main loop thread,
338 * because it prevents the main loop from processing callbacks,
339 * including timers and bottom halves.
341 * NOTE: tools currently are single-threaded and qemu_mutex_unlock_iothread
344 void qemu_mutex_unlock_iothread(void);
347 * qemu_cond_wait_iothread: Wait on condition for the main loop mutex
349 * This function atomically releases the main loop mutex and causes
350 * the calling thread to block on the condition.
352 void qemu_cond_wait_iothread(QemuCond
*cond
);
355 * qemu_cond_timedwait_iothread: like the previous, but with timeout
357 void qemu_cond_timedwait_iothread(QemuCond
*cond
, int ms
);
359 /* internal interfaces */
361 void qemu_fd_register(int fd
);
363 #define qemu_bh_new(cb, opaque) \
364 qemu_bh_new_full((cb), (opaque), (stringify(cb)))
365 QEMUBH
*qemu_bh_new_full(QEMUBHFunc
*cb
, void *opaque
, const char *name
);
366 void qemu_bh_schedule_idle(QEMUBH
*bh
);
374 typedef struct MainLoopPoll
{
380 void main_loop_poll_add_notifier(Notifier
*notify
);
381 void main_loop_poll_remove_notifier(Notifier
*notify
);