std::shared_timed_mutex (3) - Linux Manuals

std::shared_timed_mutex: std::shared_timed_mutex

NAME

std::shared_timed_mutex - std::shared_timed_mutex

Synopsis

Defined in header <shared_mutex>
class shared_timed_mutex; (since C++14)

The shared_timed_mutex class is a synchronization primitive that can be used to protect shared data from being simultaneously accessed by multiple threads. In contrast to other mutex types which facilitate exclusive access, a shared_timed_mutex has two levels of access:

* shared - several threads can share ownership of the same mutex.

* exclusive - only one thread can own the mutex.

Shared mutexes are usually used in situations when multiple readers can access the same resource at the same time without causing data races, but only one writer can do so.
In a manner similar to timed_mutex, shared_timed_mutex provides the ability to attempt to claim ownership of a shared_timed_mutex with a timeout via the try_lock_for(), try_lock_until(), try_lock_shared_for(), try_lock_shared_until() methods.
The shared_timed_mutex class satisfies all requirements of SharedTimedMutex and StandardLayoutType.

Member functions

                      constructs the mutex
constructor (public member function)
                      destroys the mutex
destructor (public member function)

operator= not copy-assignable
                      (public member function)
[deleted]

 Exclusive locking

                      locks the mutex, blocks if the mutex is not available
lock (public member function)
                      tries to lock the mutex, returns if the mutex is not available
try_lock (public member function)
                      tries to lock the mutex, returns if the mutex has been
try_lock_for unavailable for the specified timeout duration
                      (public member function)
                      tries to lock the mutex, returns if the mutex has been
try_lock_until unavailable until specified time point has been reached
                      (public member function)
                      unlocks the mutex
unlock (public member function)

Shared locking

                      locks the mutex for shared ownership, blocks if the mutex is not available
lock_shared (public member function)
                      tries to lock the mutex for shared ownership, returns if the mutex is not available
try_lock_shared (public member function)
                      tries to lock the mutex for shared ownership, returns if the mutex has been
try_lock_shared_for unavailable for the specified timeout duration
                      (public member function)
                      tries to lock the mutex for shared ownership, returns if the mutex has been
try_lock_shared_until unavailable until specified time point has been reached
                      (public member function)
                      unlocks the mutex (shared ownership)
unlock_shared (public member function)

Example

 This section is incomplete
 Reason: build a motivating example

A copy assignment operator for a class that holds resources that can handle multiple readers, but only one writer
// Run this code

  #include <mutex>
  #include <shared_mutex>

  class R
  {
      mutable std::shared_timed_mutex mut;
      /* data */
  public:
      R& operator=(const R& other)
      {
          // requires exclusive ownership to write to *this
          std::unique_lock<std::shared_timed_mutex> lhs(mut, std::defer_lock);
          // requires shared ownership to read from other
          std::shared_lock<std::shared_timed_mutex> rhs(other.mut, std::defer_lock);
          std::lock(lhs, rhs);
          /* assign data */
          return *this;
      }
  };

  int main() {
      R r;
  }