[thread.sharedtimedmutex.requirements]

The standard library type shared_timed_mutex is a shared timed mutex type.

Shared timed mutex types meet the requirements of timed mutex types ([thread.timedmutex.requirements]), shared mutex types ([thread.sharedmutex.requirements]), and additionally meet the requirements set out below.

In this description, m denotes an object of a shared timed mutex type, rel_time denotes an object of an instantiation of duration ([time.duration]), and abs_time denotes an object of an instantiation of time_point .

[Note 1:

The shared timed mutex types meet the Cpp17SharedTimedLockable requirements ([thread.req.lockable.shared.timed]).

— end note]

The expression m.try_lock_shared_for(rel_time) is well-formed and has the following semantics:

Effects: Attempts to obtain shared lock ownership for the calling thread within the relative timeout ([thread.req.timing]) specified by rel_time.

If the time specified by rel_time is less than or equal to rel_time.zero(), the function attempts to obtain ownership without blocking (as if by calling try_lock_shared()).

The function returns within the timeout specified by rel_time only if it has obtained shared ownership of the mutex object.

[Note 2:

As with try_lock(), there is no guarantee that ownership will be obtained if the lock is available, but implementations are expected to make a strong effort to do so.

— end note]

If an exception is thrown then a shared lock has not been acquired for the current thread.

Synchronization: If try_lock_shared_for() returns true, prior unlock() operations on the same object synchronize with ([intro.multithread]) this operation.

The expression m.try_lock_shared_until(abs_time) is well-formed and has the following semantics:

Effects: The function attempts to obtain shared ownership of the mutex.

If abs_time has already passed, the function attempts to obtain shared ownership without blocking (as if by calling try_lock_shared()).

The function returns before the absolute timeout ([thread.req.timing]) specified by abs_time only if it has obtained shared ownership of the mutex object.

[Note 3:

As with try_lock(), there is no guarantee that ownership will be obtained if the lock is available, but implementations are expected to make a strong effort to do so.

— end note]

If an exception is thrown then a shared lock has not been acquired for the current thread.

Synchronization: If try_lock_shared_until() returns true, prior unlock() operations on the same object synchronize with ([intro.multithread]) this operation.

Throws: Timeout-related exceptions ([thread.req.timing]).

32.6.4.5.2 Class shared_timed_mutex [thread.sharedtimedmutex.class]

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namespace std { class shared_timed_mutex { public: shared_timed_mutex(); ~shared_timed_mutex(); shared_timed_mutex(const shared_timed_mutex&) = delete; shared_timed_mutex& operator=(const shared_timed_mutex&) = delete; / exclusive ownership void lock(); / blocking bool try_lock(); template<class Rep, class Period> bool try_lock_for(const chrono::duration<Rep, Period>& rel_time); template<class Clock, class Duration> bool try_lock_until(const chrono::time_point<Clock, Duration>& abs_time); void unlock(); / shared ownership void lock_shared(); / blocking bool try_lock_shared(); template<class Rep, class Period> bool try_lock_shared_for(const chrono::duration<Rep, Period>& rel_time); template<class Clock, class Duration> bool try_lock_shared_until(const chrono::time_point<Clock, Duration>& abs_time); void unlock_shared(); }; }

The class shared_timed_mutex provides a non-recursive mutex with shared ownership semantics.

The class shared_timed_mutex meets all of the shared timed mutex requirements ([thread.sharedtimedmutex.requirements]).

It is a standard-layout class ([class.prop]).

The behavior of a program is undefined if

(3.1)
it destroys a shared_timed_mutex object owned by any thread,
(3.2)
a thread attempts to recursively gain any ownership of a shared_timed_mutex, or
(3.3)
a thread terminates while possessing any ownership of a shared_timed_mutex.