| /* |
| * QEMU coroutine implementation |
| * |
| * Copyright IBM, Corp. 2011 |
| * |
| * Authors: |
| * Stefan Hajnoczi <stefanha@linux.vnet.ibm.com> |
| * Kevin Wolf <kwolf@redhat.com> |
| * |
| * This work is licensed under the terms of the GNU LGPL, version 2 or later. |
| * See the COPYING.LIB file in the top-level directory. |
| * |
| */ |
| |
| #ifndef QEMU_COROUTINE_H |
| #define QEMU_COROUTINE_H |
| |
| #include <stdbool.h> |
| #include "qemu/typedefs.h" |
| #include "qemu/queue.h" |
| #include "qemu/timer.h" |
| |
| /** |
| * Coroutines are a mechanism for stack switching and can be used for |
| * cooperative userspace threading. These functions provide a simple but |
| * useful flavor of coroutines that is suitable for writing sequential code, |
| * rather than callbacks, for operations that need to give up control while |
| * waiting for events to complete. |
| * |
| * These functions are re-entrant and may be used outside the global mutex. |
| */ |
| |
| /** |
| * Mark a function that executes in coroutine context |
| * |
| * Functions that execute in coroutine context cannot be called directly from |
| * normal functions. In the future it would be nice to enable compiler or |
| * static checker support for catching such errors. This annotation might make |
| * it possible and in the meantime it serves as documentation. |
| * |
| * For example: |
| * |
| * static void coroutine_fn foo(void) { |
| * .... |
| * } |
| */ |
| #define coroutine_fn |
| |
| typedef struct Coroutine Coroutine; |
| |
| /** |
| * Coroutine entry point |
| * |
| * When the coroutine is entered for the first time, opaque is passed in as an |
| * argument. |
| * |
| * When this function returns, the coroutine is destroyed automatically and |
| * execution continues in the caller who last entered the coroutine. |
| */ |
| typedef void coroutine_fn CoroutineEntry(void *opaque); |
| |
| /** |
| * Create a new coroutine |
| * |
| * Use qemu_coroutine_enter() to actually transfer control to the coroutine. |
| */ |
| Coroutine *qemu_coroutine_create(CoroutineEntry *entry); |
| |
| /** |
| * Transfer control to a coroutine |
| * |
| * The opaque argument is passed as the argument to the entry point when |
| * entering the coroutine for the first time. It is subsequently ignored. |
| */ |
| void qemu_coroutine_enter(Coroutine *coroutine, void *opaque); |
| |
| /** |
| * Transfer control back to a coroutine's caller |
| * |
| * This function does not return until the coroutine is re-entered using |
| * qemu_coroutine_enter(). |
| */ |
| void coroutine_fn qemu_coroutine_yield(void); |
| |
| /** |
| * Get the currently executing coroutine |
| */ |
| Coroutine *coroutine_fn qemu_coroutine_self(void); |
| |
| /** |
| * Return whether or not currently inside a coroutine |
| * |
| * This can be used to write functions that work both when in coroutine context |
| * and when not in coroutine context. Note that such functions cannot use the |
| * coroutine_fn annotation since they work outside coroutine context. |
| */ |
| bool qemu_in_coroutine(void); |
| |
| |
| |
| /** |
| * CoQueues are a mechanism to queue coroutines in order to continue executing |
| * them later. They provide the fundamental primitives on which coroutine locks |
| * are built. |
| */ |
| typedef struct CoQueue { |
| QTAILQ_HEAD(, Coroutine) entries; |
| } CoQueue; |
| |
| /** |
| * Initialise a CoQueue. This must be called before any other operation is used |
| * on the CoQueue. |
| */ |
| void qemu_co_queue_init(CoQueue *queue); |
| |
| /** |
| * Adds the current coroutine to the CoQueue and transfers control to the |
| * caller of the coroutine. |
| */ |
| void coroutine_fn qemu_co_queue_wait(CoQueue *queue); |
| |
| /** |
| * Restarts the next coroutine in the CoQueue and removes it from the queue. |
| * |
| * Returns true if a coroutine was restarted, false if the queue is empty. |
| */ |
| bool coroutine_fn qemu_co_queue_next(CoQueue *queue); |
| |
| /** |
| * Restarts all coroutines in the CoQueue and leaves the queue empty. |
| */ |
| void coroutine_fn qemu_co_queue_restart_all(CoQueue *queue); |
| |
| /** |
| * Enter the next coroutine in the queue |
| */ |
| bool qemu_co_enter_next(CoQueue *queue); |
| |
| /** |
| * Checks if the CoQueue is empty. |
| */ |
| bool qemu_co_queue_empty(CoQueue *queue); |
| |
| |
| /** |
| * Provides a mutex that can be used to synchronise coroutines |
| */ |
| typedef struct CoMutex { |
| bool locked; |
| CoQueue queue; |
| } CoMutex; |
| |
| /** |
| * Initialises a CoMutex. This must be called before any other operation is used |
| * on the CoMutex. |
| */ |
| void qemu_co_mutex_init(CoMutex *mutex); |
| |
| /** |
| * Locks the mutex. If the lock cannot be taken immediately, control is |
| * transferred to the caller of the current coroutine. |
| */ |
| void coroutine_fn qemu_co_mutex_lock(CoMutex *mutex); |
| |
| /** |
| * Unlocks the mutex and schedules the next coroutine that was waiting for this |
| * lock to be run. |
| */ |
| void coroutine_fn qemu_co_mutex_unlock(CoMutex *mutex); |
| |
| typedef struct CoRwlock { |
| bool writer; |
| int reader; |
| CoQueue queue; |
| } CoRwlock; |
| |
| /** |
| * Initialises a CoRwlock. This must be called before any other operation |
| * is used on the CoRwlock |
| */ |
| void qemu_co_rwlock_init(CoRwlock *lock); |
| |
| /** |
| * Read locks the CoRwlock. If the lock cannot be taken immediately because |
| * of a parallel writer, control is transferred to the caller of the current |
| * coroutine. |
| */ |
| void qemu_co_rwlock_rdlock(CoRwlock *lock); |
| |
| /** |
| * Write Locks the mutex. If the lock cannot be taken immediately because |
| * of a parallel reader, control is transferred to the caller of the current |
| * coroutine. |
| */ |
| void qemu_co_rwlock_wrlock(CoRwlock *lock); |
| |
| /** |
| * Unlocks the read/write lock and schedules the next coroutine that was |
| * waiting for this lock to be run. |
| */ |
| void qemu_co_rwlock_unlock(CoRwlock *lock); |
| |
| /** |
| * Yield the coroutine for a given duration |
| * |
| * Note this function uses timers and hence only works when a main loop is in |
| * use. See main-loop.h and do not use from qemu-tool programs. |
| */ |
| void coroutine_fn co_sleep_ns(QEMUClockType type, int64_t ns); |
| |
| /** |
| * Yield the coroutine for a given duration |
| * |
| * Behaves similarly to co_sleep_ns(), but the sleeping coroutine will be |
| * resumed when using qemu_aio_wait(). |
| */ |
| void coroutine_fn co_aio_sleep_ns(AioContext *ctx, QEMUClockType type, |
| int64_t ns); |
| |
| /** |
| * Yield until a file descriptor becomes readable |
| * |
| * Note that this function clobbers the handlers for the file descriptor. |
| */ |
| void coroutine_fn yield_until_fd_readable(int fd); |
| #endif /* QEMU_COROUTINE_H */ |