C++ named requirements: Mutex

The Mutex requirements extends the Lockable requirements to include inter-thread synchronization.


For an object m of Mutex type:

(until C++17)
  • The expression m.try_lock() has the following properties
    • Behaves as an atomic operation.
    • Attempts to obtain exclusive ownership of the mutex for the calling thread without blocking. If ownership is not obtained, returns immediately. The function is allowed to spuriously fail and return even if the mutex is not currently owned by another thread.
    • If try_lock() succeeds, prior unlock() operations on the same object synchronize-with this operation (equivalent to release-acquire std::memory_order). lock() does not synchronize with a failed try_lock()
    • Does not throw exceptions.
  • The expression m.unlock() has the following properties
    • Behaves as an atomic operation.
    • Releases the calling thread's ownership of the mutex and synchronizes-with the subsequent successful lock operations on the same object.
    • The behavior is undefined if the calling thread does not own the mutex.
    • Does not throw exceptions.
  • All lock and unlock operations on a single mutex occur in a single total order that can be viewed as modification order of an atomic variable: the order is specific to this individual mutex.

Library types

The following standard library types satisfy Mutex:

See also

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