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