| /* Copyright (C) 2005 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 Lesser General Public License as published by |
| the Free Software Foundation; either version 2.1 of the License, 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 Lesser General Public License for |
| more details. |
| |
| You should have received a copy of the GNU Lesser General Public License |
| along with libgomp; see the file COPYING.LIB. If not, write to the |
| Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, |
| MA 02110-1301, USA. */ |
| |
| /* As a special exception, if you link this library with other files, some |
| of which are compiled with GCC, to produce an executable, this library |
| does not by itself cause the resulting executable to be covered by the |
| GNU General Public License. This exception does not however invalidate |
| any other reasons why the executable file might be covered by the GNU |
| General Public License. */ |
| |
| /* 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 "libgomp.h" |
| #include "futex.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; |
| } |
| futex_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); |
| } |