1 /*
2 * Copyright (C) 2018 The Android Open Source Project
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 "membarrier.h"
18
19 #include <errno.h>
20 #include <stdio.h>
21
22 #if !defined(_WIN32)
23 #include <sys/syscall.h>
24 #include <unistd.h>
25 #endif
26
27 #include "macros.h"
28 #include "utils.h"
29
30 #if __has_include(<linux/membarrier.h>)
31
32 #include <linux/membarrier.h>
33
34 #define CHECK_MEMBARRIER_CMD(art_value, membarrier_value) \
35 static_assert(static_cast<int>(art_value) == (membarrier_value), "Bad value for " # art_value)
36 CHECK_MEMBARRIER_CMD(art::MembarrierCommand::kQuery, MEMBARRIER_CMD_QUERY);
37 CHECK_MEMBARRIER_CMD(art::MembarrierCommand::kGlobal, MEMBARRIER_CMD_SHARED);
38 CHECK_MEMBARRIER_CMD(art::MembarrierCommand::kPrivateExpedited, MEMBARRIER_CMD_PRIVATE_EXPEDITED);
39 CHECK_MEMBARRIER_CMD(art::MembarrierCommand::kRegisterPrivateExpedited,
40 MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED);
41 CHECK_MEMBARRIER_CMD(art::MembarrierCommand::kPrivateExpedited, MEMBARRIER_CMD_PRIVATE_EXPEDITED);
42 #undef CHECK_MEMBARRIER_CMD
43
44 #endif // __has_include(<linux/membarrier.h>)
45
46 namespace art {
47
48 #if defined(__linux__)
49
IsMemBarrierSupported()50 static bool IsMemBarrierSupported() {
51 // Check kernel version supports membarrier(2).
52 // MEMBARRIER_CMD_QUERY is supported since Linux 4.3.
53 // MEMBARRIER_CMD_PRIVATE_EXPEDITED is supported since Linux 4.14.
54 // MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE is supported since Linux 4.16.
55 // Lowest Linux version useful for ART is 4.14.
56 return IsKernelVersionAtLeast(4, 14);
57 }
58
membarrier(MembarrierCommand command)59 int membarrier(MembarrierCommand command) {
60 static const bool membarrier_supported = IsMemBarrierSupported();
61 if (UNLIKELY(!membarrier_supported)) {
62 errno = ENOSYS;
63 return -1;
64 }
65 return syscall(__NR_membarrier, static_cast<int>(command), 0);
66 }
67
68 #else // __linux__
69
70 int membarrier([[maybe_unused]] MembarrierCommand command) {
71 errno = ENOSYS;
72 return -1;
73 }
74
75 #endif // __linux__
76
77 } // namespace art
78