1 /* Copyright (C) 2008-2021 Free Software Foundation, Inc.
2 Contributed by Jakub Jelinek <jakub@redhat.com>.
3
4 This file is part of the GNU Offloading and Multi Processing Library
5 (libgomp).
6
7 Libgomp is free software; you can redistribute it and/or modify it
8 under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 3, or (at your option)
10 any later version.
11
12 Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY
13 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
14 FOR A PARTICULAR PURPOSE. See the GNU General Public License for
15 more details.
16
17 Under Section 7 of GPL version 3, you are granted additional
18 permissions described in the GCC Runtime Library Exception, version
19 3.1, as published by the Free Software Foundation.
20
21 You should have received a copy of the GNU General Public License and
22 a copy of the GCC Runtime Library Exception along with this program;
23 see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
24 <http://www.gnu.org/licenses/>. */
25
26 /* This is a Linux specific implementation of a mutex synchronization
27 mechanism for libgomp. This type is private to the library. This
28 implementation uses atomic instructions and the futex syscall. */
29
30 #include <endian.h>
31 #include <limits.h>
32 #include "wait.h"
33
34 void *
gomp_ptrlock_get_slow(gomp_ptrlock_t * ptrlock)35 gomp_ptrlock_get_slow (gomp_ptrlock_t *ptrlock)
36 {
37 int *intptr;
38 uintptr_t oldval = 1;
39
40 __atomic_compare_exchange_n (ptrlock, &oldval, 2, false,
41 MEMMODEL_RELAXED, MEMMODEL_RELAXED);
42
43 /* futex works on ints, not pointers.
44 But a valid work share pointer will be at least
45 8 byte aligned, so it is safe to assume the low
46 32-bits of the pointer won't contain values 1 or 2. */
47 __asm volatile ("" : "=r" (intptr) : "0" (ptrlock));
48 #if __BYTE_ORDER == __BIG_ENDIAN
49 if (sizeof (*ptrlock) > sizeof (int))
50 intptr += (sizeof (*ptrlock) / sizeof (int)) - 1;
51 #endif
52 do
53 do_wait (intptr, 2);
54 while (__atomic_load_n (intptr, MEMMODEL_RELAXED) == 2);
55 __asm volatile ("" : : : "memory");
56 return (void *) __atomic_load_n (ptrlock, MEMMODEL_ACQUIRE);
57 }
58
59 void
gomp_ptrlock_set_slow(gomp_ptrlock_t * ptrlock)60 gomp_ptrlock_set_slow (gomp_ptrlock_t *ptrlock)
61 {
62 int *intptr;
63
64 __asm volatile ("" : "=r" (intptr) : "0" (ptrlock));
65 #if __BYTE_ORDER == __BIG_ENDIAN
66 if (sizeof (*ptrlock) > sizeof (int))
67 intptr += (sizeof (*ptrlock) / sizeof (int)) - 1;
68 #endif
69 futex_wake (intptr, INT_MAX);
70 }
71