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/*
* Copyright © 2013 Keith Packard
*
* Permission to use, copy, modify, distribute, and sell this software and its
* documentation for any purpose is hereby granted without fee, provided that
* the above copyright notice appear in all copies and that both that copyright
* notice and this permission notice appear in supporting documentation, and
* that the name of the copyright holders not be used in advertising or
* publicity pertaining to distribution of the software without specific,
* written prior permission. The copyright holders make no representations
* about the suitability of this software for any purpose. It is provided "as
* is" without express or implied warranty.
*
* THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
* INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
* EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
* CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
* DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
* TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
* OF THIS SOFTWARE.
*/
#if HAVE_CONFIG_H
#include "config.h"
#endif
#include "xshmfenceint.h"
/**
* xshmfence_trigger:
* @f: An X fence
*
* Set @f to triggered, waking all waiters.
*
* Return value: 0 on success and -1 on error (in which case, errno
* will be set as appropriate).
**/
int
xshmfence_trigger(struct xshmfence *f)
{
if (__sync_val_compare_and_swap(&f->v, 0, 1) == -1) {
atomic_store(&f->v, 1);
if (futex_wake(&f->v) < 0)
return -1;
}
return 0;
}
/**
* xshmfence_await:
* @f: An X fence
*
* Wait for @f to be triggered. If @f is already triggered, this
* function returns immediately.
*
* Return value: 0 on success and -1 on error (in which case, errno
* will be set as appropriate).
**/
int
xshmfence_await(struct xshmfence *f)
{
while (__sync_val_compare_and_swap(&f->v, 0, -1) != 1) {
if (futex_wait(&f->v, -1)) {
if (errno != EWOULDBLOCK)
return -1;
}
}
return 0;
}
/**
* xshmfence_query:
* @f: An X fence
*
* Return value: 1 if @f is triggered, else returns 0.
**/
int
xshmfence_query(struct xshmfence *f)
{
return atomic_fetch(&f->v) == 1;
}
/**
* xshmfence_reset:
* @f: An X fence
*
* Reset @f to untriggered. If @f is already untriggered,
* this function has no effect.
**/
void
xshmfence_reset(struct xshmfence *f)
{
__sync_bool_compare_and_swap(&f->v, 1, 0);
}
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