| (since C++11) |
Locks the associated mutex. Effectively calls mutex()->lock().
Parameters
(none).
Return value
(none).
Exceptions
- Any exceptions thrown by
mutex()->lock() - If there is no associated mutex,
std::system_errorwith an error code ofstd::errc::operation_not_permitted - If the mutex is already locked by this
unique_lock(in other words, owns_lock is true),std::system_errorwith an error code ofstd::errc::resource_deadlock_would_occur
Example
The following example uses lock to re-acquire a mutex that was unlocked.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 | #include <mutex>#include <thread>#include <iostream>#include <vector>#include <chrono> int main(){ int counter = 0; std::mutex counter_mutex; std::vector<std::thread> threads; auto worker_task = [&](int id) { std::unique_lock<std::mutex> lock(counter_mutex); ++counter; std::cout << id << ", initial counter: " << counter << '\n'; lock.unlock(); // don't hold the lock while we simulate an expensive operation std::this_thread::sleep_for(std::chrono::seconds(1)); lock.lock(); ++counter; std::cout << id << ", final counter: " << counter << '\n'; }; for (int i = 0; i < 10; ++i) threads.emplace_back(worker_task, i); for (auto &thread : threads) thread.join();} |
Possible output:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 | 0, initial counter: 11, initial counter: 22, initial counter: 33, initial counter: 44, initial counter: 55, initial counter: 66, initial counter: 77, initial counter: 88, initial counter: 99, initial counter: 106, final counter: 113, final counter: 124, final counter: 132, final counter: 145, final counter: 150, final counter: 161, final counter: 177, final counter: 189, final counter: 198, final counter: 20 |
See also
| tries to lock the associated mutex, returns if the mutex is not available (public member function) | |
| unlocks the associated mutex (public member function) |
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