#ifndef QEMU_COROUTINE_H
#define QEMU_COROUTINE_H
-#include "qemu/typedefs.h"
#include "qemu/queue.h"
#include "qemu/timer.h"
* Create a new coroutine
*
* Use qemu_coroutine_enter() to actually transfer control to the coroutine.
+ * The opaque argument is passed as the argument to the entry point.
*/
-Coroutine *qemu_coroutine_create(CoroutineEntry *entry);
+Coroutine *qemu_coroutine_create(CoroutineEntry *entry, void *opaque);
/**
* 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);
+void qemu_coroutine_enter(Coroutine *coroutine);
+
+/**
+ * Transfer control to a coroutine if it's not active (i.e. part of the call
+ * stack of the running coroutine). Otherwise, do nothing.
+ */
+void qemu_coroutine_enter_if_inactive(Coroutine *co);
+
+/**
+ * Transfer control to a coroutine and associate it with ctx
+ */
+void qemu_aio_coroutine_enter(AioContext *ctx, Coroutine *co);
/**
* Transfer control back to a coroutine's caller
*/
void coroutine_fn qemu_coroutine_yield(void);
+/**
+ * Get the AioContext of the given coroutine
+ */
+AioContext *coroutine_fn qemu_coroutine_get_aio_context(Coroutine *co);
+
/**
* Get the currently executing coroutine
*/
*/
bool qemu_in_coroutine(void);
+/**
+ * Return true if the coroutine is currently entered
+ *
+ * A coroutine is "entered" if it has not yielded from the current
+ * qemu_coroutine_enter() call used to run it. This does not mean that the
+ * coroutine is currently executing code since it may have transferred control
+ * to another coroutine using qemu_coroutine_enter().
+ *
+ * When several coroutines enter each other there may be no way to know which
+ * ones have already been entered. In such situations this function can be
+ * used to avoid recursively entering coroutines.
+ */
+bool qemu_coroutine_entered(Coroutine *co);
+
+/**
+ * Provides a mutex that can be used to synchronise coroutines
+ */
+struct CoWaitRecord;
+struct CoMutex {
+ /* Count of pending lockers; 0 for a free mutex, 1 for an
+ * uncontended mutex.
+ */
+ unsigned locked;
+
+ /* Context that is holding the lock. Useful to avoid spinning
+ * when two coroutines on the same AioContext try to get the lock. :)
+ */
+ AioContext *ctx;
+
+ /* A queue of waiters. Elements are added atomically in front of
+ * from_push. to_pop is only populated, and popped from, by whoever
+ * is in charge of the next wakeup. This can be an unlocker or,
+ * through the handoff protocol, a locker that is about to go to sleep.
+ */
+ QSLIST_HEAD(, CoWaitRecord) from_push, to_pop;
+
+ unsigned handoff, sequence;
+
+ Coroutine *holder;
+};
+
+/**
+ * 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);
/**
* 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.
+ * them later. They are similar to condition variables, but they need help
+ * from an external mutex in order to maintain thread-safety.
*/
typedef struct CoQueue {
- QTAILQ_HEAD(, Coroutine) entries;
+ QSIMPLEQ_HEAD(, Coroutine) entries;
} CoQueue;
/**
/**
* Adds the current coroutine to the CoQueue and transfers control to the
- * caller of the coroutine.
+ * caller of the coroutine. The mutex is unlocked during the wait and
+ * locked again afterwards.
*/
-void coroutine_fn qemu_co_queue_wait(CoQueue *queue);
+#define qemu_co_queue_wait(queue, lock) \
+ qemu_co_queue_wait_impl(queue, QEMU_MAKE_LOCKABLE(lock))
+void coroutine_fn qemu_co_queue_wait_impl(CoQueue *queue, QemuLockable *lock);
/**
- * 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.
+ * Removes the next coroutine from the CoQueue, and wake it up.
+ * Returns true if a coroutine was removed, 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.
+ * Empties the CoQueue; all coroutines are woken up.
*/
void coroutine_fn qemu_co_queue_restart_all(CoQueue *queue);
/**
- * Enter the next coroutine in the queue
+ * Removes the next coroutine from the CoQueue, and wake it up. Unlike
+ * qemu_co_queue_next, this function releases the lock during aio_co_wake
+ * because it is meant to be used outside coroutine context; in that case, the
+ * coroutine is entered immediately, before qemu_co_enter_next returns.
+ *
+ * If used in coroutine context, qemu_co_enter_next is equivalent to
+ * qemu_co_queue_next.
*/
-bool qemu_co_enter_next(CoQueue *queue);
+#define qemu_co_enter_next(queue, lock) \
+ qemu_co_enter_next_impl(queue, QEMU_MAKE_LOCKABLE(lock))
+bool qemu_co_enter_next_impl(CoQueue *queue, QemuLockable *lock);
/**
* 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 pending_writer;
int reader;
+ CoMutex mutex;
CoQueue queue;
} CoRwlock;
*/
void qemu_co_rwlock_rdlock(CoRwlock *lock);
+/**
+ * Write Locks the CoRwlock from a reader. This is a bit more efficient than
+ * @qemu_co_rwlock_unlock followed by a separate @qemu_co_rwlock_wrlock.
+ * However, if the lock cannot be upgraded immediately, control is transferred
+ * to the caller of the current coroutine. Also, @qemu_co_rwlock_upgrade
+ * only overrides CoRwlock fairness if there are no concurrent readers, so
+ * another writer might run while @qemu_co_rwlock_upgrade blocks.
+ */
+void qemu_co_rwlock_upgrade(CoRwlock *lock);
+
+/**
+ * Downgrades a write-side critical section to a reader. Downgrading with
+ * @qemu_co_rwlock_downgrade never blocks, unlike @qemu_co_rwlock_unlock
+ * followed by @qemu_co_rwlock_rdlock. This makes it more efficient, but
+ * may also sometimes be necessary for correctness.
+ */
+void qemu_co_rwlock_downgrade(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
/**
* Yield the coroutine for a given duration
- *
- * Behaves similarly to co_sleep_ns(), but the sleeping coroutine will be
- * resumed when using aio_poll().
*/
-void coroutine_fn co_aio_sleep_ns(AioContext *ctx, QEMUClockType type,
- int64_t ns);
+void coroutine_fn qemu_co_sleep_ns(QEMUClockType type, int64_t ns);
/**
* Yield until a file descriptor becomes readable
*/
void coroutine_fn yield_until_fd_readable(int fd);
+#include "qemu/lockable.h"
+
#endif /* QEMU_COROUTINE_H */
projects / qemu.git / blobdiff