374 lines
14 KiB
C
374 lines
14 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
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#include "block/aio.h"
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#define SIG_IPI SIGUSR1
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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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* In the case of QEMU tools, this will also start/initialize timers.
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*/
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int qemu_init_main_loop(Error **errp);
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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);
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* }
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*
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* ...
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* QEMUCoroutine *co = qemu_coroutine_create(coroutine_entry, NULL);
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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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void main_loop_wait(int nonblocking);
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/**
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* qemu_get_aio_context: Return the main loop's AioContext
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*/
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AioContext *qemu_get_aio_context(void);
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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.
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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 currently 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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/**
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* IOCanReadHandler: Return the number of bytes that #IOReadHandler can accept
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*
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* This function reports how many bytes #IOReadHandler is prepared to accept.
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* #IOReadHandler may be invoked with up to this number of bytes. If this
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* function returns 0 then #IOReadHandler is not invoked.
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*
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* This function is typically called from an event loop. If the number of
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* bytes changes outside the event loop (e.g. because a vcpu thread drained the
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* buffer), then it is necessary to kick the event loop so that this function
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* is called again. aio_notify() or qemu_notify_event() can be used to kick
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* the event loop.
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*/
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typedef int IOCanReadHandler(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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void 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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/**
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* event_notifier_set_handler: Register an EventNotifier with the main loop
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*
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* This function tells the main loop to wake up whenever the
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* #EventNotifier was set.
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*
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* @e: The #EventNotifier to be observed.
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*
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* @handler: A level-triggered callback that is fired when @e
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* has been set. @e is passed to it as a parameter.
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*/
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void event_notifier_set_handler(EventNotifier *e,
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EventNotifierHandler *handler);
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GSource *iohandler_get_g_source(void);
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AioContext *iohandler_get_aio_context(void);
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/**
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* qemu_mutex_iothread_locked: Return lock status of the main loop mutex.
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*
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* The main loop mutex is the coarsest lock in QEMU, and as such it
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* must always be taken outside other locks. This function helps
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* functions take different paths depending on whether the current
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* thread is running within the main loop mutex.
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*
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* This function should never be used in the block layer, because
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* unit tests, block layer tools and qemu-storage-daemon do not
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* have a BQL.
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* Please instead refer to qemu_in_main_thread().
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*/
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bool qemu_mutex_iothread_locked(void);
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/**
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* qemu_in_main_thread: return whether it's possible to safely access
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* the global state of the block layer.
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*
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* Global state of the block layer is not accessible from I/O threads
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* or worker threads; only from threads that "own" the default
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* AioContext that qemu_get_aio_context() returns. For tests, block
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* layer tools and qemu-storage-daemon there is a designated thread that
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* runs the event loop for qemu_get_aio_context(), and that is the
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* main thread.
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*
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* For emulators, however, any thread that holds the BQL can act
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* as the block layer main thread; this will be any of the actual
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* main thread, the vCPU threads or the RCU thread.
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*
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* For clarity, do not use this function outside the block layer.
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*/
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bool qemu_in_main_thread(void);
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/* Mark and check that the function is part of the global state API. */
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#ifdef CONFIG_COCOA
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/*
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* When using the Cocoa UI, addRemovableDevicesMenuItems() is called from
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* a thread different from the QEMU main thread and can not take the BQL,
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* triggering this assertions in the block layer (commit 0439c5a462).
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* As the Cocoa fix is not trivial, disable this assertion for the v7.0.0
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* release (when using Cocoa); we will restore it immediately after the
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* release.
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* This issue is tracked as https://gitlab.com/qemu-project/qemu/-/issues/926
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*/
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#define GLOBAL_STATE_CODE()
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#else
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#define GLOBAL_STATE_CODE() \
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do { \
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/* FIXME: Re-enable after 7.0 release */ \
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/* assert(qemu_in_main_thread()); */ \
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} while (0)
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#endif /* CONFIG_COCOA */
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/* Mark and check that the function is part of the I/O API. */
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#define IO_CODE() \
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do { \
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/* nop */ \
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} while (0)
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/* Mark and check that the function is part of the "I/O OR GS" API. */
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#define IO_OR_GS_CODE() \
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do { \
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/* nop */ \
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} while (0)
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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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* main() in vl.c 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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* NOTE: tools currently are single-threaded and qemu_mutex_lock_iothread
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* is a no-op there.
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*/
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#define qemu_mutex_lock_iothread() \
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qemu_mutex_lock_iothread_impl(__FILE__, __LINE__)
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void qemu_mutex_lock_iothread_impl(const char *file, int line);
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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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* main() in vl.c 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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* NOTE: tools currently are single-threaded and qemu_mutex_unlock_iothread
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* is a no-op there.
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*/
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void qemu_mutex_unlock_iothread(void);
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/*
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* qemu_cond_wait_iothread: Wait on condition for the main loop mutex
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*
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* This function atomically releases the main loop mutex and causes
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* the calling thread to block on the condition.
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*/
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void qemu_cond_wait_iothread(QemuCond *cond);
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/*
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* qemu_cond_timedwait_iothread: like the previous, but with timeout
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*/
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void qemu_cond_timedwait_iothread(QemuCond *cond, int ms);
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/* internal interfaces */
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void qemu_fd_register(int fd);
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#define qemu_bh_new(cb, opaque) \
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qemu_bh_new_full((cb), (opaque), (stringify(cb)))
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QEMUBH *qemu_bh_new_full(QEMUBHFunc *cb, void *opaque, const char *name);
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void qemu_bh_schedule_idle(QEMUBH *bh);
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enum {
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MAIN_LOOP_POLL_FILL,
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MAIN_LOOP_POLL_ERR,
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MAIN_LOOP_POLL_OK,
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};
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typedef struct MainLoopPoll {
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int state;
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uint32_t timeout;
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GArray *pollfds;
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} MainLoopPoll;
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void main_loop_poll_add_notifier(Notifier *notify);
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void main_loop_poll_remove_notifier(Notifier *notify);
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#endif
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