/*
* 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
#include "block/aio.h"
#include "qom/object.h"
#include "sysemu/event-loop-base.h"
#define SIG_IPI SIGUSR1
#define TYPE_MAIN_LOOP "main-loop"
OBJECT_DECLARE_TYPE(MainLoop, MainLoopClass, MAIN_LOOP)
struct MainLoop {
EventLoopBase parent_obj;
};
typedef struct MainLoop MainLoop;
/**
* 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(Error **errp);
/**
* 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);
* }
*
* ...
* QEMUCoroutine *co = qemu_coroutine_create(coroutine_entry, NULL);
* 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.
*/
void main_loop_wait(int nonblocking);
/**
* qemu_get_aio_context: Return the main loop's AioContext
*/
AioContext *qemu_get_aio_context(void);
/**
* 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.
*/
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);
/**
* IOCanReadHandler: Return the number of bytes that #IOReadHandler can accept
*
* This function reports how many bytes #IOReadHandler is prepared to accept.
* #IOReadHandler may be invoked with up to this number of bytes. If this
* function returns 0 then #IOReadHandler is not invoked.
*
* This function is typically called from an event loop. If the number of
* bytes changes outside the event loop (e.g. because a vcpu thread drained the
* buffer), then it is necessary to kick the event loop so that this function
* is called again. aio_notify() or qemu_notify_event() can be used to kick
* the event loop.
*/
typedef int IOCanReadHandler(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.
*/
void qemu_set_fd_handler(int fd,
IOHandler *fd_read,
IOHandler *fd_write,
void *opaque);
/**
* event_notifier_set_handler: Register an EventNotifier with the main loop
*
* This function tells the main loop to wake up whenever the
* #EventNotifier was set.
*
* @e: The #EventNotifier to be observed.
*
* @handler: A level-triggered callback that is fired when @e
* has been set. @e is passed to it as a parameter.
*/
void event_notifier_set_handler(EventNotifier *e,
EventNotifierHandler *handler);
GSource *iohandler_get_g_source(void);
AioContext *iohandler_get_aio_context(void);
/**
* qemu_mutex_iothread_locked: Return lock status of the main loop mutex.
*
* The main loop mutex is the coarsest lock in QEMU, and as such it
* must always be taken outside other locks. This function helps
* functions take different paths depending on whether the current
* thread is running within the main loop mutex.
*
* This function should never be used in the block layer, because
* unit tests, block layer tools and qemu-storage-daemon do not
* have a BQL.
* Please instead refer to qemu_in_main_thread().
*/
bool qemu_mutex_iothread_locked(void);
/**
* qemu_in_main_thread: return whether it's possible to safely access
* the global state of the block layer.
*
* Global state of the block layer is not accessible from I/O threads
* or worker threads; only from threads that "own" the default
* AioContext that qemu_get_aio_context() returns. For tests, block
* layer tools and qemu-storage-daemon there is a designated thread that
* runs the event loop for qemu_get_aio_context(), and that is the
* main thread.
*
* For emulators, however, any thread that holds the BQL can act
* as the block layer main thread; this will be any of the actual
* main thread, the vCPU threads or the RCU thread.
*
* For clarity, do not use this function outside the block layer.
*/
bool qemu_in_main_thread(void);
/* Mark and check that the function is part of the global state API. */
#ifdef CONFIG_COCOA
/*
* When using the Cocoa UI, addRemovableDevicesMenuItems() is called from
* a thread different from the QEMU main thread and can not take the BQL,
* triggering this assertions in the block layer (commit 0439c5a462).
* As the Cocoa fix is not trivial, disable this assertion for the v7.0.0
* release (when using Cocoa); we will restore it immediately after the
* release.
* This issue is tracked as https://gitlab.com/qemu-project/qemu/-/issues/926
*/
#define GLOBAL_STATE_CODE()
#else
#define GLOBAL_STATE_CODE() \
do { \
assert(qemu_in_main_thread()); \
} while (0)
#endif /* CONFIG_COCOA */
/* Mark and check that the function is part of the I/O API. */
#define IO_CODE() \
do { \
/* nop */ \
} while (0)
/* Mark and check that the function is part of the "I/O OR GS" API. */
#define IO_OR_GS_CODE() \
do { \
/* nop */ \
} while (0)
/**
* qemu_mutex_lock_iothread: Lock the main loop mutex.
*
* This function locks the main loop mutex. The mutex is taken by
* main() in vl.c 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.
*/
#define qemu_mutex_lock_iothread() \
qemu_mutex_lock_iothread_impl(__FILE__, __LINE__)
void qemu_mutex_lock_iothread_impl(const char *file, int line);
/**
* qemu_mutex_unlock_iothread: Unlock the main loop mutex.
*
* This function unlocks the main loop mutex. The mutex is taken by
* main() in vl.c 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);
/*
* qemu_cond_wait_iothread: Wait on condition for the main loop mutex
*
* This function atomically releases the main loop mutex and causes
* the calling thread to block on the condition.
*/
void qemu_cond_wait_iothread(QemuCond *cond);
/*
* qemu_cond_timedwait_iothread: like the previous, but with timeout
*/
void qemu_cond_timedwait_iothread(QemuCond *cond, int ms);
/* internal interfaces */
void qemu_fd_register(int fd);
#define qemu_bh_new(cb, opaque) \
qemu_bh_new_full((cb), (opaque), (stringify(cb)))
QEMUBH *qemu_bh_new_full(QEMUBHFunc *cb, void *opaque, const char *name);
void qemu_bh_schedule_idle(QEMUBH *bh);
enum {
MAIN_LOOP_POLL_FILL,
MAIN_LOOP_POLL_ERR,
MAIN_LOOP_POLL_OK,
};
typedef struct MainLoopPoll {
int state;
uint32_t timeout;
GArray *pollfds;
} MainLoopPoll;
void main_loop_poll_add_notifier(Notifier *notify);
void main_loop_poll_remove_notifier(Notifier *notify);
#endif
