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std::timed_mutex::try_lock_for(3) | C++ Standard Libary | std::timed_mutex::try_lock_for(3) |
NAME¶
std::timed_mutex::try_lock_for - std::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.
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¶
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)
2022.07.31 | http://cppreference.com |