1169695Skan/* Copyright (C) 2005 Free Software Foundation, Inc. 2169695Skan Contributed by Richard Henderson <rth@redhat.com>. 3169695Skan 4169695Skan This file is part of the GNU OpenMP Library (libgomp). 5169695Skan 6169695Skan Libgomp is free software; you can redistribute it and/or modify it 7169695Skan under the terms of the GNU Lesser General Public License as published by 8169695Skan the Free Software Foundation; either version 2.1 of the License, or 9169695Skan (at your option) any later version. 10169695Skan 11169695Skan Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY 12169695Skan WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS 13169695Skan FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for 14169695Skan more details. 15169695Skan 16169695Skan You should have received a copy of the GNU Lesser General Public License 17169695Skan along with libgomp; see the file COPYING.LIB. If not, write to the 18169695Skan Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, 19169695Skan MA 02110-1301, USA. */ 20169695Skan 21169695Skan/* As a special exception, if you link this library with other files, some 22169695Skan of which are compiled with GCC, to produce an executable, this library 23169695Skan does not by itself cause the resulting executable to be covered by the 24169695Skan GNU General Public License. This exception does not however invalidate 25169695Skan any other reasons why the executable file might be covered by the GNU 26169695Skan General Public License. */ 27169695Skan 28169695Skan/* This is a Linux specific implementation of a semaphore synchronization 29169695Skan mechanism for libgomp. This type is private to the library. This 30169695Skan implementation uses atomic instructions and the futex syscall. */ 31169695Skan 32169695Skan#include "libgomp.h" 33169695Skan#include "futex.h" 34169695Skan 35169695Skan 36169695Skanvoid 37169695Skangomp_sem_wait_slow (gomp_sem_t *sem) 38169695Skan{ 39169695Skan while (1) 40169695Skan { 41169695Skan int val = __sync_val_compare_and_swap (sem, 0, -1); 42169695Skan if (val > 0) 43169695Skan { 44169695Skan if (__sync_bool_compare_and_swap (sem, val, val - 1)) 45169695Skan return; 46169695Skan } 47169695Skan futex_wait (sem, -1); 48169695Skan } 49169695Skan} 50169695Skan 51169695Skanvoid 52169695Skangomp_sem_post_slow (gomp_sem_t *sem) 53169695Skan{ 54169695Skan int old, tmp = *sem, wake; 55169695Skan 56169695Skan do 57169695Skan { 58169695Skan old = tmp; 59169695Skan wake = old > 0 ? old + 1 : 1; 60169695Skan tmp = __sync_val_compare_and_swap (sem, old, wake); 61169695Skan } 62169695Skan while (old != tmp); 63169695Skan 64169695Skan futex_wake (sem, wake); 65169695Skan} 66