352 lines
13 KiB
C
352 lines
13 KiB
C
/*
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* QEMU System Emulator
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*
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* Copyright (c) 2003-2008 Fabrice Bellard
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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#ifndef QEMU_MAIN_LOOP_H
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#define QEMU_MAIN_LOOP_H 1
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#ifdef SIGRTMIN
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#define SIG_IPI (SIGRTMIN+4)
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#else
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#define SIG_IPI SIGUSR1
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#endif
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/**
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* qemu_init_main_loop: Set up the process so that it can run the main loop.
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*
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* This includes setting up signal handlers. It should be called before
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* any other threads are created. In addition, threads other than the
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* main one should block signals that are trapped by the main loop.
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* For simplicity, you can consider these signals to be safe: SIGUSR1,
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* SIGUSR2, thread signals (SIGFPE, SIGILL, SIGSEGV, SIGBUS) and real-time
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* signals if available. Remember that Windows in practice does not have
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* signals, though.
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*/
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int qemu_init_main_loop(void);
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/**
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* main_loop_wait: Run one iteration of the main loop.
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*
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* If @nonblocking is true, poll for events, otherwise suspend until
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* one actually occurs. The main loop usually consists of a loop that
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* repeatedly calls main_loop_wait(false).
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*
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* Main loop services include file descriptor callbacks, bottom halves
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* and timers (defined in qemu-timer.h). Bottom halves are similar to timers
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* that execute immediately, but have a lower overhead and scheduling them
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* is wait-free, thread-safe and signal-safe.
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*
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* It is sometimes useful to put a whole program in a coroutine. In this
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* case, the coroutine actually should be started from within the main loop,
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* so that the main loop can run whenever the coroutine yields. To do this,
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* you can use a bottom half to enter the coroutine as soon as the main loop
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* starts:
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*
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* void enter_co_bh(void *opaque) {
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* QEMUCoroutine *co = opaque;
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* qemu_coroutine_enter(co, NULL);
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* }
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*
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* ...
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* QEMUCoroutine *co = qemu_coroutine_create(coroutine_entry);
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* QEMUBH *start_bh = qemu_bh_new(enter_co_bh, co);
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* qemu_bh_schedule(start_bh);
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* while (...) {
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* main_loop_wait(false);
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* }
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*
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* (In the future we may provide a wrapper for this).
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*
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* @nonblocking: Whether the caller should block until an event occurs.
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*/
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int main_loop_wait(int nonblocking);
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/**
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* qemu_notify_event: Force processing of pending events.
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*
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* Similar to signaling a condition variable, qemu_notify_event forces
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* main_loop_wait to look at pending events and exit. The caller of
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* main_loop_wait will usually call it again very soon, so qemu_notify_event
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* also has the side effect of recalculating the sets of file descriptors
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* that the main loop waits for.
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*
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* Calling qemu_notify_event is rarely necessary, because main loop
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* services (bottom halves and timers) call it themselves. One notable
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* exception occurs when using qemu_set_fd_handler2 (see below).
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*/
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void qemu_notify_event(void);
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#ifdef _WIN32
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/* return TRUE if no sleep should be done afterwards */
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typedef int PollingFunc(void *opaque);
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/**
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* qemu_add_polling_cb: Register a Windows-specific polling callback
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*
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* Currently, under Windows some events are polled rather than waited for.
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* Polling callbacks do not ensure that @func is called timely, because
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* the main loop might wait for an arbitrarily long time. If possible,
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* you should instead create a separate thread that does a blocking poll
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* and set a Win32 event object. The event can then be passed to
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* qemu_add_wait_object.
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*
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* Polling callbacks really have nothing Windows specific in them, but
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* as they are a hack and are currenly not necessary under POSIX systems,
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* they are only available when QEMU is running under Windows.
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*
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* @func: The function that does the polling, and returns 1 to force
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* immediate completion of main_loop_wait.
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* @opaque: A pointer-size value that is passed to @func.
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*/
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int qemu_add_polling_cb(PollingFunc *func, void *opaque);
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/**
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* qemu_del_polling_cb: Unregister a Windows-specific polling callback
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*
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* This function removes a callback that was registered with
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* qemu_add_polling_cb.
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*
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* @func: The function that was passed to qemu_add_polling_cb.
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* @opaque: A pointer-size value that was passed to qemu_add_polling_cb.
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*/
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void qemu_del_polling_cb(PollingFunc *func, void *opaque);
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/* Wait objects handling */
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typedef void WaitObjectFunc(void *opaque);
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/**
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* qemu_add_wait_object: Register a callback for a Windows handle
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*
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* Under Windows, the iohandler mechanism can only be used with sockets.
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* QEMU must use the WaitForMultipleObjects API to wait on other handles.
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* This function registers a #HANDLE with QEMU, so that it will be included
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* in the main loop's calls to WaitForMultipleObjects. When the handle
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* is in a signaled state, QEMU will call @func.
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*
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* @handle: The Windows handle to be observed.
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* @func: A function to be called when @handle is in a signaled state.
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* @opaque: A pointer-size value that is passed to @func.
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*/
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int qemu_add_wait_object(HANDLE handle, WaitObjectFunc *func, void *opaque);
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/**
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* qemu_del_wait_object: Unregister a callback for a Windows handle
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*
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* This function removes a callback that was registered with
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* qemu_add_wait_object.
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*
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* @func: The function that was passed to qemu_add_wait_object.
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* @opaque: A pointer-size value that was passed to qemu_add_wait_object.
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*/
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void qemu_del_wait_object(HANDLE handle, WaitObjectFunc *func, void *opaque);
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#endif
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/* async I/O support */
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typedef void IOReadHandler(void *opaque, const uint8_t *buf, int size);
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typedef int IOCanReadHandler(void *opaque);
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typedef void IOHandler(void *opaque);
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/**
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* qemu_set_fd_handler2: Register a file descriptor with the main loop
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*
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* This function tells the main loop to wake up whenever one of the
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* following conditions is true:
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*
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* 1) if @fd_write is not %NULL, when the file descriptor is writable;
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*
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* 2) if @fd_read is not %NULL, when the file descriptor is readable.
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*
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* @fd_read_poll can be used to disable the @fd_read callback temporarily.
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* This is useful to avoid calling qemu_set_fd_handler2 every time the
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* client becomes interested in reading (or dually, stops being interested).
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* A typical example is when @fd is a listening socket and you want to bound
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* the number of active clients. Remember to call qemu_notify_event whenever
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* the condition may change from %false to %true.
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*
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* The callbacks that are set up by qemu_set_fd_handler2 are level-triggered.
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* If @fd_read does not read from @fd, or @fd_write does not write to @fd
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* until its buffers are full, they will be called again on the next
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* iteration.
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*
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* @fd: The file descriptor to be observed. Under Windows it must be
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* a #SOCKET.
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*
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* @fd_read_poll: A function that returns 1 if the @fd_read callback
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* should be fired. If the function returns 0, the main loop will not
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* end its iteration even if @fd becomes readable.
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*
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* @fd_read: A level-triggered callback that is fired if @fd is readable
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* at the beginning of a main loop iteration, or if it becomes readable
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* during one.
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*
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* @fd_write: A level-triggered callback that is fired when @fd is writable
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* at the beginning of a main loop iteration, or if it becomes writable
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* during one.
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*
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* @opaque: A pointer-sized value that is passed to @fd_read_poll,
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* @fd_read and @fd_write.
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*/
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int qemu_set_fd_handler2(int fd,
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IOCanReadHandler *fd_read_poll,
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IOHandler *fd_read,
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IOHandler *fd_write,
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void *opaque);
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/**
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* qemu_set_fd_handler: Register a file descriptor with the main loop
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*
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* This function tells the main loop to wake up whenever one of the
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* following conditions is true:
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*
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* 1) if @fd_write is not %NULL, when the file descriptor is writable;
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*
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* 2) if @fd_read is not %NULL, when the file descriptor is readable.
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*
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* The callbacks that are set up by qemu_set_fd_handler are level-triggered.
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* If @fd_read does not read from @fd, or @fd_write does not write to @fd
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* until its buffers are full, they will be called again on the next
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* iteration.
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*
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* @fd: The file descriptor to be observed. Under Windows it must be
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* a #SOCKET.
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*
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* @fd_read: A level-triggered callback that is fired if @fd is readable
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* at the beginning of a main loop iteration, or if it becomes readable
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* during one.
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*
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* @fd_write: A level-triggered callback that is fired when @fd is writable
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* at the beginning of a main loop iteration, or if it becomes writable
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* during one.
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*
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* @opaque: A pointer-sized value that is passed to @fd_read and @fd_write.
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*/
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int qemu_set_fd_handler(int fd,
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IOHandler *fd_read,
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IOHandler *fd_write,
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void *opaque);
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typedef struct QEMUBH QEMUBH;
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typedef void QEMUBHFunc(void *opaque);
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/**
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* qemu_bh_new: Allocate a new bottom half structure.
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*
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* Bottom halves are lightweight callbacks whose invocation is guaranteed
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* to be wait-free, thread-safe and signal-safe. The #QEMUBH structure
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* is opaque and must be allocated prior to its use.
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*/
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QEMUBH *qemu_bh_new(QEMUBHFunc *cb, void *opaque);
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/**
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* qemu_bh_schedule: Schedule a bottom half.
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*
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* Scheduling a bottom half interrupts the main loop and causes the
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* execution of the callback that was passed to qemu_bh_new.
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*
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* Bottom halves that are scheduled from a bottom half handler are instantly
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* invoked. This can create an infinite loop if a bottom half handler
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* schedules itself.
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*
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* @bh: The bottom half to be scheduled.
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*/
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void qemu_bh_schedule(QEMUBH *bh);
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/**
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* qemu_bh_cancel: Cancel execution of a bottom half.
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*
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* Canceling execution of a bottom half undoes the effect of calls to
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* qemu_bh_schedule without freeing its resources yet. While cancellation
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* itself is also wait-free and thread-safe, it can of course race with the
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* loop that executes bottom halves unless you are holding the iothread
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* mutex. This makes it mostly useless if you are not holding the mutex.
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*
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* @bh: The bottom half to be canceled.
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*/
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void qemu_bh_cancel(QEMUBH *bh);
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/**
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*qemu_bh_delete: Cancel execution of a bottom half and free its resources.
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*
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* Deleting a bottom half frees the memory that was allocated for it by
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* qemu_bh_new. It also implies canceling the bottom half if it was
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* scheduled.
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*
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* @bh: The bottom half to be deleted.
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*/
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void qemu_bh_delete(QEMUBH *bh);
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#ifdef CONFIG_POSIX
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/**
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* qemu_add_child_watch: Register a child process for reaping.
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*
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* Under POSIX systems, a parent process must read the exit status of
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* its child processes using waitpid, or the operating system will not
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* free some of the resources attached to that process.
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*
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* This function directs the QEMU main loop to observe a child process
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* and call waitpid as soon as it exits; the watch is then removed
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* automatically. It is useful whenever QEMU forks a child process
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* but will find out about its termination by other means such as a
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* "broken pipe".
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*
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* @pid: The pid that QEMU should observe.
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*/
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int qemu_add_child_watch(pid_t pid);
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#endif
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/**
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* qemu_mutex_lock_iothread: Lock the main loop mutex.
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*
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* This function locks the main loop mutex. The mutex is taken by
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* qemu_init_main_loop and always taken except while waiting on
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* external events (such as with select). The mutex should be taken
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* by threads other than the main loop thread when calling
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* qemu_bh_new(), qemu_set_fd_handler() and basically all other
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* functions documented in this file.
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*/
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void qemu_mutex_lock_iothread(void);
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/**
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* qemu_mutex_unlock_iothread: Unlock the main loop mutex.
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*
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* This function unlocks the main loop mutex. The mutex is taken by
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* qemu_init_main_loop and always taken except while waiting on
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* external events (such as with select). The mutex should be unlocked
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* as soon as possible by threads other than the main loop thread,
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* because it prevents the main loop from processing callbacks,
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* including timers and bottom halves.
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*/
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void qemu_mutex_unlock_iothread(void);
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/* internal interfaces */
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void qemu_iohandler_fill(int *pnfds, fd_set *readfds, fd_set *writefds, fd_set *xfds);
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void qemu_iohandler_poll(fd_set *readfds, fd_set *writefds, fd_set *xfds, int rc);
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void qemu_bh_schedule_idle(QEMUBH *bh);
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int qemu_bh_poll(void);
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void qemu_bh_update_timeout(int *timeout);
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#endif
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