1/*
2 * Copyright 2016-present Facebook, Inc.
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#include <folly/portability/SysMembarrier.h>
18
19#include <mutex>
20
21#include <folly/Portability.h>
22#include <folly/portability/SysSyscall.h>
23#include <folly/portability/Unistd.h>
24
25#if FOLLY_X64 && !FOLLY_MOBILE && defined(__linux__)
26#define FOLLY_USE_SYS_MEMBARRIER 1
27#if !defined(__NR_membarrier)
28#define __NR_membarrier 324
29#endif
30#if __has_include(<linux/membarrier.h>)
31#include <linux/membarrier.h> // @manual
32#else
33#define MEMBARRIER_CMD_QUERY 0
34#define MEMBARRIER_CMD_SHARED 1
35#endif
36#endif
37
38namespace folly {
39namespace detail {
40
41bool sysMembarrierAvailable() {
42 if (!kIsLinux) {
43 return false;
44 }
45
46#if FOLLY_USE_SYS_MEMBARRIER
47 auto r = syscall(__NR_membarrier, MEMBARRIER_CMD_QUERY, /* flags = */ 0);
48 if (r == -1) {
49 return false;
50 }
51
52 return r & MEMBARRIER_CMD_SHARED;
53#else
54 return false;
55#endif
56}
57
58int sysMembarrier() {
59#if FOLLY_USE_SYS_MEMBARRIER
60 return syscall(__NR_membarrier, MEMBARRIER_CMD_SHARED, /* flags = */ 0);
61#else
62 return -1;
63#endif
64}
65} // namespace detail
66} // namespace folly
67