| /* Copyright (C) 2005, 2008, 2009 Free Software Foundation, Inc. |
| Contributed by Richard Henderson <rth@redhat.com>. |
| |
| This file is part of the GNU OpenMP Library (libgomp). |
| |
| Libgomp is free software; you can redistribute it and/or modify it |
| under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 3, or (at your option) |
| any later version. |
| |
| Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY |
| WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS |
| FOR A PARTICULAR PURPOSE. See the GNU General Public License for |
| more details. |
| |
| Under Section 7 of GPL version 3, you are granted additional |
| permissions described in the GCC Runtime Library Exception, version |
| 3.1, as published by the Free Software Foundation. |
| |
| You should have received a copy of the GNU General Public License and |
| a copy of the GCC Runtime Library Exception along with this program; |
| see the files COPYING3 and COPYING.RUNTIME respectively. If not, see |
| <http://www.gnu.org/licenses/>. */ |
| |
| /* This is a Linux specific implementation of a semaphore synchronization |
| mechanism for libgomp. This type is private to the library. This |
| implementation uses atomic instructions and the futex syscall. */ |
| |
| #include "wait.h" |
| |
| |
| void |
| gomp_sem_wait_slow (gomp_sem_t *sem) |
| { |
| while (1) |
| { |
| int val = __sync_val_compare_and_swap (sem, 0, -1); |
| if (val > 0) |
| { |
| if (__sync_bool_compare_and_swap (sem, val, val - 1)) |
| return; |
| } |
| do_wait (sem, -1); |
| } |
| } |
| |
| void |
| gomp_sem_post_slow (gomp_sem_t *sem) |
| { |
| int old, tmp = *sem, wake; |
| |
| do |
| { |
| old = tmp; |
| wake = old > 0 ? old + 1 : 1; |
| tmp = __sync_val_compare_and_swap (sem, old, wake); |
| } |
| while (old != tmp); |
| |
| futex_wake (sem, wake); |
| } |