std::mutex - cppreference.com (original) (raw)
| | | | | ------------ | | ------------- | | class mutex; | | (since C++11) |
The mutex class is a synchronization primitive that can be used to protect shared data from being simultaneously accessed by multiple threads.
mutex offers exclusive, non-recursive ownership semantics:
- A calling thread owns a
mutexfrom the time that it successfully calls either lock or try_lock until it calls unlock. - When a thread owns a
mutex, all other threads will block (for calls to lock) or receive a false return value (for try_lock) if they attempt to claim ownership of themutex. - A calling thread must not own the
mutexprior to calling lock or try_lock.
The behavior of a program is undefined if a mutex is destroyed while still owned by any threads, or a thread terminates while owning a mutex. The mutex class satisfies all requirements of Mutex and StandardLayoutType.
std::mutex is neither copyable nor movable.
Contents
[edit] Nested types
| Name | Definition |
|---|---|
| native_handle_type (optional*) | implementation-defined[edit] |
[edit] Member functions
| (constructor) | constructs the mutex (public member function) [edit] |
|---|---|
| (destructor) | destroys the mutex (public member function) [edit] |
| operator=[deleted] | not copy-assignable (public member function) [edit] |
| Locking | |
| lock | locks the mutex, blocks if the mutex is not available (public member function) [edit] |
| try_lock | tries to lock the mutex, returns if the mutex is not available (public member function) [edit] |
| unlock | unlocks the mutex (public member function) [edit] |
| Native handle | |
| native_handle | returns the underlying implementation-defined native handle object (public member function) [edit] |
[edit] Notes
std::mutex is usually not accessed directly: std::unique_lock, std::lock_guard, or std::scoped_lock(since C++17) manage locking in a more exception-safe manner.
[edit] Example
This example shows how a mutex can be used to protect an std::map shared between two threads.
Output:
http://bar => fake content http://foo => fake content