| /* 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_ */ |