void lock(); | (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.
#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:
0, initial counter: 1 1, initial counter: 2 2, initial counter: 3 3, initial counter: 4 4, initial counter: 5 5, initial counter: 6 6, initial counter: 7 7, initial counter: 8 8, initial counter: 9 9, initial counter: 10 6, final counter: 11 3, final counter: 12 4, final counter: 13 2, final counter: 14 5, final counter: 15 0, final counter: 16 1, final counter: 17 7, final counter: 18 9, final counter: 19 8, 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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