NAME¶

std::recursive_timed_mutex::try_lock_for - std::recursive_timed_mutex::try_lock_for

Synopsis¶

template< class Rep, class Period >
bool try_lock_for( const std::chrono::duration<Rep,Period>& (since C++11)
timeout_duration );

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.

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.

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¶

lock locks the mutex, blocks if the mutex is not available
(public member function)
try_lock 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
try_lock_until unavailable until specified time point has been reached
(public member function)
unlock unlocks the mutex
(public member function)