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/* Copyright (c) 2013, Ben Noordhuis <info@bnoordhuis.nl>
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, 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.
*/
#ifndef UV_SPINLOCK_H_
#define UV_SPINLOCK_H_
#include "internal.h" /* ACCESS_ONCE, UV_UNUSED */
#include "atomic-ops.h"
#define UV_SPINLOCK_INITIALIZER { 0 }
typedef struct {
int lock;
} uv_spinlock_t;
UV_UNUSED(static void uv_spinlock_init(uv_spinlock_t* spinlock));
UV_UNUSED(static void uv_spinlock_lock(uv_spinlock_t* spinlock));
UV_UNUSED(static void uv_spinlock_unlock(uv_spinlock_t* spinlock));
UV_UNUSED(static int uv_spinlock_trylock(uv_spinlock_t* spinlock));
UV_UNUSED(static void uv_spinlock_init(uv_spinlock_t* spinlock)) {
ACCESS_ONCE(int, spinlock->lock) = 0;
}
UV_UNUSED(static void uv_spinlock_lock(uv_spinlock_t* spinlock)) {
while (!uv_spinlock_trylock(spinlock)) cpu_relax();
}
UV_UNUSED(static void uv_spinlock_unlock(uv_spinlock_t* spinlock)) {
ACCESS_ONCE(int, spinlock->lock) = 0;
}
UV_UNUSED(static int uv_spinlock_trylock(uv_spinlock_t* spinlock)) {
/* TODO(bnoordhuis) Maybe change to a ticket lock to guarantee fair queueing.
* Not really critical until we have locks that are (frequently) contended
* for by several threads.
*/
return 0 == cmpxchgi(&spinlock->lock, 0, 1);
}
#endif /* UV_SPINLOCK_H_ */
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