Chapter 86: Recursive Mutex

Section 86.1: std::recursive_mutex

Recursive mutex allows the same thread to recursively lock a resource - up to an unspecified limit.

There are very few real-word justifications for this. Certain complex implementations might need to call an overloaded copy of a function without releasing the lock.

std::atomic_int temp{0}; std::recursive_mutex _mutex;

//launch_deferred launches asynchronous tasks on the same thread id

auto future1 = std::async( std::launch::deferred, [&]()

{

std::cout << std::this_thread::get_id() << std::endl;

std::this_thread::sleep_for(std::chrono::seconds(3)); std::unique_lock<std::recursive_mutex> lock( _mutex); temp=0;

});

auto future2 = std::async( std::launch::deferred, [&]()

{

std::cout << std::this_thread::get_id() << std::endl; while ( true )

{

std::this_thread::sleep_for(std::chrono::milliseconds(1)); std::unique_lock<std::recursive_mutex> lock( _mutex, std::try_to_lock); if ( temp < INT_MAX )

temp++;

cout << temp << endl;

}

}); future1.get(); future2.get();