diff options
Diffstat (limited to 'util/rfifolock.c')
-rw-r--r-- | util/rfifolock.c | 78 |
1 files changed, 0 insertions, 78 deletions
diff --git a/util/rfifolock.c b/util/rfifolock.c deleted file mode 100644 index 084c2f0ea1..0000000000 --- a/util/rfifolock.c +++ /dev/null @@ -1,78 +0,0 @@ -/* - * Recursive FIFO lock - * - * Copyright Red Hat, Inc. 2013 - * - * Authors: - * Stefan Hajnoczi <stefanha@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. - * - */ - -#include "qemu/osdep.h" -#include "qemu/rfifolock.h" - -void rfifolock_init(RFifoLock *r, void (*cb)(void *), void *opaque) -{ - qemu_mutex_init(&r->lock); - r->head = 0; - r->tail = 0; - qemu_cond_init(&r->cond); - r->nesting = 0; - r->cb = cb; - r->cb_opaque = opaque; -} - -void rfifolock_destroy(RFifoLock *r) -{ - qemu_cond_destroy(&r->cond); - qemu_mutex_destroy(&r->lock); -} - -/* - * Theory of operation: - * - * In order to ensure FIFO ordering, implement a ticketlock. Threads acquiring - * the lock enqueue themselves by incrementing the tail index. When the lock - * is unlocked, the head is incremented and waiting threads are notified. - * - * Recursive locking does not take a ticket since the head is only incremented - * when the outermost recursive caller unlocks. - */ -void rfifolock_lock(RFifoLock *r) -{ - qemu_mutex_lock(&r->lock); - - /* Take a ticket */ - unsigned int ticket = r->tail++; - - if (r->nesting > 0 && qemu_thread_is_self(&r->owner_thread)) { - r->tail--; /* put ticket back, we're nesting */ - } else { - while (ticket != r->head) { - /* Invoke optional contention callback */ - if (r->cb) { - r->cb(r->cb_opaque); - } - qemu_cond_wait(&r->cond, &r->lock); - } - qemu_thread_get_self(&r->owner_thread); - } - - r->nesting++; - qemu_mutex_unlock(&r->lock); -} - -void rfifolock_unlock(RFifoLock *r) -{ - qemu_mutex_lock(&r->lock); - assert(r->nesting > 0); - assert(qemu_thread_is_self(&r->owner_thread)); - if (--r->nesting == 0) { - r->head++; - qemu_cond_broadcast(&r->cond); - } - qemu_mutex_unlock(&r->lock); -} |