std::timed_mutex::lock

void lock();		(since C++11)

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, the behavior is undefined: for example, the program may deadlock. An implementation that can detect the invalid usage is encouraged to throw a std::system_error with error condition resource_deadlock_would_occur instead of deadlocking.

Prior unlock() operations on the same mutex synchronize-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, std::scoped_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 <chrono>
#include <iostream>
#include <mutex>
#include <thread>
 
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;
        // note, that the mutex also syncronizes the output
        std::cout << "id: " << id << ", g_num: " << g_num << '\n';
        g_num_mutex.unlock();
 
        std::this_thread::sleep_for(std::chrono::milliseconds(234));
    }
}
 
int main()
{
    std::thread t1{slow_increment, 0};
    std::thread t2{slow_increment, 1};
    t1.join();
    t2.join();
}

Possible output:

id: 0, g_num: 1
id: 1, g_num: 2
id: 1, g_num: 3
id: 0, g_num: 4
id: 0, g_num: 5
id: 1, g_num: 6

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

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Member functions
timed_mutex::timed_mutex
timed_mutex::~timed_mutex
Locking
timed_mutex::lock
timed_mutex::try_lock
timed_mutex::try_lock_for
timed_mutex::try_lock_until
timed_mutex::unlock
Native handle
timed_mutex::native_handle