disas: QOMify target specific setup
[qemu/cris-port.git] / util / rfifolock.c
blobafbf7488df0c9faef76884ba24d5ab70481f927e
1 /*
2 * Recursive FIFO lock
4 * Copyright Red Hat, Inc. 2013
6 * Authors:
7 * Stefan Hajnoczi <stefanha@redhat.com>
9 * This work is licensed under the terms of the GNU LGPL, version 2 or later.
10 * See the COPYING.LIB file in the top-level directory.
14 #include <assert.h>
15 #include "qemu/rfifolock.h"
17 void rfifolock_init(RFifoLock *r, void (*cb)(void *), void *opaque)
19 qemu_mutex_init(&r->lock);
20 r->head = 0;
21 r->tail = 0;
22 qemu_cond_init(&r->cond);
23 r->nesting = 0;
24 r->cb = cb;
25 r->cb_opaque = opaque;
28 void rfifolock_destroy(RFifoLock *r)
30 qemu_cond_destroy(&r->cond);
31 qemu_mutex_destroy(&r->lock);
35 * Theory of operation:
37 * In order to ensure FIFO ordering, implement a ticketlock. Threads acquiring
38 * the lock enqueue themselves by incrementing the tail index. When the lock
39 * is unlocked, the head is incremented and waiting threads are notified.
41 * Recursive locking does not take a ticket since the head is only incremented
42 * when the outermost recursive caller unlocks.
44 void rfifolock_lock(RFifoLock *r)
46 qemu_mutex_lock(&r->lock);
48 /* Take a ticket */
49 unsigned int ticket = r->tail++;
51 if (r->nesting > 0 && qemu_thread_is_self(&r->owner_thread)) {
52 r->tail--; /* put ticket back, we're nesting */
53 } else {
54 while (ticket != r->head) {
55 /* Invoke optional contention callback */
56 if (r->cb) {
57 r->cb(r->cb_opaque);
59 qemu_cond_wait(&r->cond, &r->lock);
63 qemu_thread_get_self(&r->owner_thread);
64 r->nesting++;
65 qemu_mutex_unlock(&r->lock);
68 void rfifolock_unlock(RFifoLock *r)
70 qemu_mutex_lock(&r->lock);
71 assert(r->nesting > 0);
72 assert(qemu_thread_is_self(&r->owner_thread));
73 if (--r->nesting == 0) {
74 r->head++;
75 qemu_cond_broadcast(&r->cond);
77 qemu_mutex_unlock(&r->lock);