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std::recursive_timed_mutex::try_lock_for

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std::recursive_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().

A steady clock is used to measure the duration. This function may block for longer than timeout_duration due to scheduling or resource contention delays.

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.

A thread may call try_lock_for on a recursive mutex repeatedly. Successful calls to try_lock_for increment the ownership count: the mutex will only be released after the thread makes a matching number of calls to unlock.

The maximum number of levels of ownership is unspecified. A call to try_lock_for will return false if this number is exceeded.

Contents

[edit] Parameters

timeout_duration - maximum duration to block for

[edit] Return value

true if the lock was acquired successfully, otherwise false.

[edit] 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)

[edit] Example

Run this code
#include <iostream>
#include <mutex>
#include <thread>
#include <vector>
#include <sstream>
 
std::mutex cout_mutex; // control access to std::cout
std::timed_mutex mutex;
 
void job(int id) 
{
    using Ms = std::chrono::milliseconds;
    std::ostringstream stream;
 
    for (int i = 0; i < 3; ++i) {
        if (mutex.try_lock_for(Ms(100))) {
            stream << "success ";
            std::this_thread::sleep_for(Ms(100));
            mutex.unlock();
        } else {
            stream << "failed ";
        }
        std::this_thread::sleep_for(Ms(100));
    }
 
    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

[edit] See also

 locks the mutex, blocks if the mutex is not available
(public member function) [edit]
tries to lock the mutex, returns if the mutex is not available
(public member function) [edit]
tries to lock the mutex, returns if the mutex has been
unavailable until specified time point has been reached
(public member function) [edit]
unlocks the mutex
(public member function) [edit]
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