std::shared_timed_mutex::lock

 

C++

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std::shared_timed_mutex

Member functions

shared_timed_mutex::shared_timed_mutex

Exclusive locking

shared_timed_mutex::lock

shared_timed_mutex::try_lock

shared_timed_mutex::try_lock_for

shared_timed_mutex::try_lock_until

shared_timed_mutex::unlock

Shared locking

shared_timed_mutex::lock_shared

shared_timed_mutex::try_lock_shared

shared_timed_mutex::try_lock_shared_for

shared_timed_mutex::try_lock_shared_until

shared_timed_mutex::unlock_shared

 

void lock();		(since C++14)

Locks the mutex. If another thread has already locked the mutex, a call to lock will block execution until the lock is acquired.

If lock is called by a thread that already owns the mutex in any mode (shared or exclusive), the behavior is undefined.

Prior unlock() operation on the same mutex synchronizes-with (as defined in std::memory_order) this operation.

Parameters

(none)

Return value

(none)

Exceptions

Throws std::system_error when errors occur, including errors from the underlying operating system that would prevent lock from meeting its specifications. The mutex is not locked in the case of any exception being thrown.

Notes

lock() is usually not called directly: std::unique_lock and std::lock_guard are used to manage exclusive locking.

Example

This example shows how lock and unlock can be used to protect shared data.

Run this code

#include <iostream>
#include <chrono>
#include <thread>
#include <mutex>
 
int g_num = 0;  // protected by g_num_mutex
std::mutex g_num_mutex;
 
void slow_increment(int id) 
{
    for (int i = 0; i < 3; ++i) {
        g_num_mutex.lock();
        ++g_num;
        std::cout << id << " => " << g_num << '\n';
        g_num_mutex.unlock();
 
        std::this_thread::sleep_for(std::chrono::seconds(1));
    }
}
 
int main()
{
    std::thread t1(slow_increment, 0);
    std::thread t2(slow_increment, 1);
    t1.join();
    t2.join();
}

Possible output:

0 => 1
1 => 2
0 => 3
1 => 4
0 => 5
1 => 6

See also

try_lock	tries to lock the mutex, returns if the mutex is not available (public member function)
unlock	unlocks the mutex (public member function)