|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Defined in header <mutex> | ||
template<class Lockable1,class Lockable2,class...LockableN> int try_lock( Lockable1& lock1, Lockable2& lock2, LockableN&...lockn); | (since C++11) | |
Tries to lock each of the givenLockable objectslock1,lock2,...,lockn by callingtry_lock in order beginning with the first.
If a call totry_lock fails, no further call totry_lock is performed,unlock is called for any locked objects and a0-based index of the object that failed to lock is returned.
If a call totry_lock results in an exception,unlock is called for any locked objects before rethrowing.
Contents |
| lock1, lock2, ..., lockn | - | theLockable objects to lock |
-1 on success, or0-based index value of the object that failed to lock.
The following example usesstd::try_lock to periodically tally and reset counters running in separate threads.
#include <chrono>#include <functional>#include <iostream>#include <mutex>#include <thread>#include <vector> int main(){int foo_count=0;std::mutex foo_count_mutex;int bar_count=0;std::mutex bar_count_mutex;int overall_count=0;bool done=false;std::mutex done_mutex; auto increment=[](int& counter,std::mutex& m,constchar* desc){for(int i=0; i<10;++i){std::unique_lock<std::mutex> lock(m);++counter;std::cout<< desc<<": "<< counter<<'\n'; lock.unlock();std::this_thread::sleep_for(std::chrono::seconds(1));}}; std::thread increment_foo(increment,std::ref(foo_count),std::ref(foo_count_mutex),"foo");std::thread increment_bar(increment,std::ref(bar_count),std::ref(bar_count_mutex),"bar"); std::thread update_overall([&](){ done_mutex.lock();while(!done){ done_mutex.unlock();int result= std::try_lock(foo_count_mutex, bar_count_mutex);if(result==-1){ overall_count+= foo_count+ bar_count; foo_count=0; bar_count=0;std::cout<<"overall: "<< overall_count<<'\n'; foo_count_mutex.unlock(); bar_count_mutex.unlock();}std::this_thread::sleep_for(std::chrono::seconds(2)); done_mutex.lock();} done_mutex.unlock();}); increment_foo.join(); increment_bar.join(); done_mutex.lock(); done=true; done_mutex.unlock(); update_overall.join(); std::cout<<"Done processing\n"<<"foo: "<< foo_count<<'\n'<<"bar: "<< bar_count<<'\n'<<"overall: "<< overall_count<<'\n';}
Possible output:
bar: 1foo: 1foo: 2bar: 2foo: 3overall: 5bar: 1foo: 1bar: 2foo: 2bar: 3overall: 10bar: 1foo: 1bar: 2foo: 2overall: 14bar: 1foo: 1bar: 2overall: 17foo: 1bar: 1foo: 2overall: 20Done processingfoo: 0bar: 0overall: 20
(C++11) | locks specified mutexes, blocks if any are unavailable (function template)[edit] |
