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