std::mutex::unlock - cppreference.com (original) (raw)

| void unlock(); | | (since C++11) | | -------------- | | ------------- |

Unlocks the mutex. The mutex must be locked by the current thread of execution, otherwise, the behavior is undefined.

This operation synchronizes-with (as defined in std::memory_order) any subsequent lock operation that obtains ownership of the same mutex.

[edit] Notes

unlock() is usually not called directly: std::unique_lock and std::lock_guard are used to manage exclusive locking.

[edit] Example

This example shows how lock and unlock can be used to protect shared data.

#include #include #include #include   int g_num = 0; // protected by g_num_mutex std::mutex g_num_mutex;   void slow_increment(int id) { for (int i = 0; i < 3; ++i) { g_num_mutex.lock(); int g_num_running = ++g_num; g_num_mutex.unlock(); std::cout << id << " => " << g_num_running << '\n';   std::this_thread::sleep_for(std::chrono::seconds(1)); } }   int main() { std::thread t1(slow_increment, 0); std::thread t2(slow_increment, 1); t1.join(); t2.join(); }

Possible output:

0 => 1 1 => 2 0 => 3 1 => 4 0 => 5 1 => 6

[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] | | |