| // Copyright 2021 The Fuchsia Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #ifndef SRC_STORAGE_LIB_VFS_CPP_SHARED_MUTEX_H_ |
| #define SRC_STORAGE_LIB_VFS_CPP_SHARED_MUTEX_H_ |
| |
| #include <zircon/compiler.h> |
| |
| #include <shared_mutex> |
| |
| namespace fs { |
| |
| // Drop-in replacement for std::shared_lock that has thread safety annotations. The current libcxx |
| // implementation does not have these annotations, and thus don't work correctly. |
| // |
| // TODO(https://fxbug.dev/42080556): this can be removed replaced with std::shared_lock if we update |
| // to an implementation that is annotated with the correct thread capabilities. |
| class __TA_SCOPED_CAPABILITY SharedLock { |
| public: |
| __WARN_UNUSED_CONSTRUCTOR explicit SharedLock(std::shared_mutex& m) __TA_ACQUIRE_SHARED(m) |
| : lock_(m) {} |
| // It seems like this should be __TA_RELEASE_SHARED instead of __TA_RELEASE but |
| // __TA_RELEASE_SHARED gives errors when a ScopedLock goes out of scope: |
| // |
| // releasing mutex using shared access, expected exclusive access |
| // |
| // This is probably a compiler bug. |
| ~SharedLock() __TA_RELEASE() {} |
| |
| void lock() __TA_ACQUIRE_SHARED() { lock_.lock(); } |
| // Same comment about __TA_RELEASE vs. __TA_RELEASE_SHARED as in the destructor. |
| void unlock() __TA_RELEASE() { lock_.unlock(); } |
| |
| private: |
| std::shared_lock<std::shared_mutex> lock_; |
| }; |
| |
| } // namespace fs |
| |
| #endif // SRC_STORAGE_LIB_VFS_CPP_SHARED_MUTEX_H_ |