2 * Copyright © 2013 Keith Packard
4 * Permission to use, copy, modify, distribute, and sell this software and its
5 * documentation for any purpose is hereby granted without fee, provided that
6 * the above copyright notice appear in all copies and that both that copyright
7 * notice and this permission notice appear in supporting documentation, and
8 * that the name of the copyright holders not be used in advertising or
9 * publicity pertaining to distribution of the software without specific,
10 * written prior permission. The copyright holders make no representations
11 * about the suitability of this software for any purpose. It is provided "as
12 * is" without express or implied warranty.
14 * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
15 * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
16 * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
17 * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
18 * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
19 * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
27 #include "xshmfenceint.h"
33 * Set @f to triggered, waking all waiters.
35 * Return value: 0 on success and -1 on error (in which case, errno
36 * will be set as appropriate).
39 xshmfence_trigger(struct xshmfence *f)
41 if (__sync_val_compare_and_swap(&f->v, 0, 1) == -1) {
42 atomic_store(&f->v, 1);
43 if (futex_wake(&f->v) < 0)
53 * Wait for @f to be triggered. If @f is already triggered, this
54 * function returns immediately.
56 * Return value: 0 on success and -1 on error (in which case, errno
57 * will be set as appropriate).
60 xshmfence_await(struct xshmfence *f)
62 while (__sync_val_compare_and_swap(&f->v, 0, -1) != 1) {
63 if (futex_wait(&f->v, -1)) {
64 if (errno != EWOULDBLOCK)
75 * Return value: 1 if @f is triggered, else returns 0.
78 xshmfence_query(struct xshmfence *f)
80 return atomic_fetch(&f->v) == 1;
87 * Reset @f to untriggered. If @f is already untriggered,
88 * this function has no effect.
91 xshmfence_reset(struct xshmfence *f)
93 __sync_bool_compare_and_swap(&f->v, 1, 0);