std::timed_mutex::try_lock_for

From cppreference.com
< cpp‎ | thread‎ | timed mutex

 
C++
 
Concurrency support library
Threads
(C++11)
(C++20)
(C++20)
(C++20)
(C++20)
(C++17)(C++17)    
this_thread namespace
(C++11)
(C++11)
(C++11)
(C++11)
Atomic types
(C++11)
(C++20)
(C++11)
Initialization of atomic types
(C++11)(deprecated in C++20)
(C++11)(deprecated in C++20)
(C++11)
Free functions for atomic operations
(C++11)(C++11)
(C++11)(C++11)
(C++11)(C++11)
(C++11)(C++11)(C++11)(C++11)
(C++11)(C++11)
(C++11)(C++11)
(C++11)(C++11)
(C++11)(C++11)
(C++11)(C++11)
(C++11)
(C++20)(C++20)
(C++20)
(C++20)
Free functions for atomic flags
(C++11)(C++11)
(C++11)(C++11)
(C++20)(C++20)
(C++20)(C++20)
(C++20)
(C++20)
Memory ordering
(C++11)
(C++11)
(C++11)
(C++11)
Mutual exclusion
(C++11)
(C++11)
(C++17)
Generic lock management
(C++11)
(C++17)
(C++11)
(C++14)
(C++11)(C++11)(C++11)
(C++11)
(C++11)
(C++11)(C++11)(C++11)
(C++11)
(C++11)
Condition variables
(C++11)
(C++11)
(C++11)
(C++11)
Semaphores
(C++20)(C++20)
Latches and barriers
(C++20)
(C++20)
Futures
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
 
std::timed_mutex
 
template< class Rep, class Period >
bool try_lock_for( const std::chrono::duration<Rep,Period>& timeout_duration );
 (since C++11)

Tries to lock the mutex. Blocks until specified timeout_duration has elapsed or the lock is acquired, whichever comes first. On successful lock acquisition returns true, otherwise returns false.

If timeout_duration is less or equal timeout_duration.zero(), the function behaves like try_lock().

This function may block for longer than timeout_duration due to scheduling or resource contention delays.

The standard recommends that a steady_clock is used to measure the duration. If an implementation uses a system_clock instead, the wait time may also be sensitive to clock adjustments.

As with try_lock(), this function is allowed to fail spuriously and return false even if the mutex was not locked by any other thread at some point during timeout_duration.

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

If try_lock_for is called by a thread that already owns the mutex, the behavior is undefined.

Parameters

timeout_duration - minimum duration to block for

Return value

true if the lock was acquired successfully, otherwise false.

Exceptions

Any exception thrown by clock, time_point, or duration during the execution (clocks, time points, and durations provided by the standard library never throw)

Example

Run this code
#include <iostream>
#include <mutex>
#include <chrono>
#include <thread>
#include <vector>
#include <sstream>
using namespace std::chrono_literals;
 
std::mutex cout_mutex; // control access to std::cout
std::timed_mutex mutex;
 
void job(int id)
{
    std::ostringstream stream;
 
    for (int i = 0; i < 3; ++i) {
        if (mutex.try_lock_for(100ms)) {
            stream << "success ";
            std::this_thread::sleep_for(100ms);
            mutex.unlock();
        } else {
            stream << "failed ";
        }
        std::this_thread::sleep_for(100ms);
    }
 
    std::lock_guard<std::mutex> lock{cout_mutex};
    std::cout << "[" << id << "] " << stream.str() << "\n";
}
 
int main()
{
    std::vector<std::thread> threads;
    for (int i = 0; i < 4; ++i) {
        threads.emplace_back(job, i);
    }
 
    for (auto& i: threads) {
        i.join();
    }
}

Possible output: 

[0] failed failed failed 
[3] failed failed success 
[2] failed success failed 
[1] success failed success

See also

 locks the mutex, blocks if the mutex is not available
(public member function)
tries to lock the mutex, returns if the mutex is not available
(public member function)
tries to lock the mutex, returns if the mutex has been
unavailable until specified time point has been reached
(public member function)
unlocks the mutex
(public member function)
Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/thread/timed_mutex/try_lock_for&oldid=51452"