| /* Copyright (C) 2008-2021 Free Software Foundation, Inc. |
| Contributed by Jakub Jelinek <jakub@redhat.com>. |
| |
| This file is part of the GNU Offloading and Multi Processing 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 mutex synchronization |
| mechanism for libgomp. This type is private to the library. This |
| implementation uses atomic instructions and the futex syscall. */ |
| |
| #include <endian.h> |
| #include <limits.h> |
| #include "wait.h" |
| |
| void * |
| gomp_ptrlock_get_slow (gomp_ptrlock_t *ptrlock) |
| { |
| int *intptr; |
| uintptr_t oldval = 1; |
| |
| __atomic_compare_exchange_n (ptrlock, &oldval, 2, false, |
| MEMMODEL_RELAXED, MEMMODEL_RELAXED); |
| |
| /* futex works on ints, not pointers. |
| But a valid work share pointer will be at least |
| 8 byte aligned, so it is safe to assume the low |
| 32-bits of the pointer won't contain values 1 or 2. */ |
| __asm volatile ("" : "=r" (intptr) : "0" (ptrlock)); |
| #if __BYTE_ORDER == __BIG_ENDIAN |
| if (sizeof (*ptrlock) > sizeof (int)) |
| intptr += (sizeof (*ptrlock) / sizeof (int)) - 1; |
| #endif |
| do |
| do_wait (intptr, 2); |
| while (__atomic_load_n (intptr, MEMMODEL_RELAXED) == 2); |
| __asm volatile ("" : : : "memory"); |
| return (void *) __atomic_load_n (ptrlock, MEMMODEL_ACQUIRE); |
| } |
| |
| void |
| gomp_ptrlock_set_slow (gomp_ptrlock_t *ptrlock) |
| { |
| int *intptr; |
| |
| __asm volatile ("" : "=r" (intptr) : "0" (ptrlock)); |
| #if __BYTE_ORDER == __BIG_ENDIAN |
| if (sizeof (*ptrlock) > sizeof (int)) |
| intptr += (sizeof (*ptrlock) / sizeof (int)) - 1; |
| #endif |
| futex_wake (intptr, INT_MAX); |
| } |