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- /*
- * Copyright 2016-present Facebook, Inc.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
- #include <folly/portability/SysMembarrier.h>
- #include <mutex>
- #include <folly/Portability.h>
- #include <folly/portability/SysSyscall.h>
- #include <folly/portability/Unistd.h>
- #if FOLLY_X64 && !FOLLY_MOBILE && defined(__linux__)
- #define FOLLY_USE_SYS_MEMBARRIER 1
- #if !defined(__NR_membarrier)
- #define __NR_membarrier 324
- #endif
- #if __has_include(<linux/membarrier.h>)
- #include <linux/membarrier.h> // @manual
- #else
- #define MEMBARRIER_CMD_QUERY 0
- #define MEMBARRIER_CMD_SHARED 1
- #endif
- #endif
- namespace folly {
- namespace detail {
- bool sysMembarrierAvailable() {
- if (!kIsLinux) {
- return false;
- }
- #if FOLLY_USE_SYS_MEMBARRIER
- auto r = syscall(__NR_membarrier, MEMBARRIER_CMD_QUERY, /* flags = */ 0);
- if (r == -1) {
- return false;
- }
- return r & MEMBARRIER_CMD_SHARED;
- #else
- return false;
- #endif
- }
- int sysMembarrier() {
- #if FOLLY_USE_SYS_MEMBARRIER
- return syscall(__NR_membarrier, MEMBARRIER_CMD_SHARED, /* flags = */ 0);
- #else
- return -1;
- #endif
- }
- } // namespace detail
- } // namespace folly
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