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 | |
38 | namespace folly { |
39 | namespace detail { |
40 | |
41 | bool 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 | |
58 | int 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 |