Archipelago » qemu

/*

 * 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.

 */

int qemu_init_main_loop(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