1 /* Copyright (C) 2010-2013 Free Software Foundation, Inc. 2 Contributed by ARM Ltd. 3 4 This file is part of the GNU OpenMP Library (libgomp). 5 6 Libgomp is free software; you can redistribute it and/or modify it 7 under the terms of the GNU General Public License as published by 8 the Free Software Foundation; either version 3, or (at your option) 9 any later version. 10 11 Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY 12 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS 13 FOR A PARTICULAR PURPOSE. See the GNU General Public License for 14 more details. 15 16 Under Section 7 of GPL version 3, you are granted additional 17 permissions described in the GCC Runtime Library Exception, version 18 3.1, as published by the Free Software Foundation. 19 20 You should have received a copy of the GNU General Public License and 21 a copy of the GCC Runtime Library Exception along with this program; 22 see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 23 <http://www.gnu.org/licenses/>. */ 24 25 /* Provide target-specific access to the futex system call. */ 26 27 /* The include file hierachy above us (wait.h) has pushed visibility 28 hidden, this will be applied to prototypes with headers we include 29 with the effect that we cannot link against an external function 30 (syscall). The solution here is to push default visibility, include 31 our required headers then reinstante the original visibility. */ 32 33 #pragma GCC visibility push(default) 34 35 #define _GNU_SOURCE 36 #include <unistd.h> 37 #include <sys/syscall.h> 38 39 #pragma GCC visibility pop 40 41 static inline void 42 futex_wait (int *addr, int val) 43 { 44 int err = syscall (SYS_futex, addr, gomp_futex_wait, val, NULL); 45 if (__builtin_expect (err < 0 && errno == ENOSYS, 0)) 46 { 47 gomp_futex_wait &= ~FUTEX_PRIVATE_FLAG; 48 gomp_futex_wake &= ~FUTEX_PRIVATE_FLAG; 49 syscall (SYS_futex, addr, gomp_futex_wait, val, NULL); 50 } 51 } 52 53 static inline void 54 futex_wake (int *addr, int count) 55 { 56 int err = syscall (SYS_futex, addr, gomp_futex_wake, count); 57 if (__builtin_expect (err < 0 && errno == ENOSYS, 0)) 58 { 59 gomp_futex_wait &= ~FUTEX_PRIVATE_FLAG; 60 gomp_futex_wake &= ~FUTEX_PRIVATE_FLAG; 61 syscall (SYS_futex, addr, gomp_futex_wake, count); 62 } 63 } 64 65 static inline void 66 cpu_relax (void) 67 { 68 __asm volatile ("" : : : "memory"); 69 } 70