std::condition_variable::notify_one

From cppreference.com


void notify_one();		(since C++11)

If any thread is waiting on *this, unblocks one of the waiting threads.

#include <iostream>
#include <condition_variable>
#include <thread>
#include <chrono>
std::condition_variable cv;
std::mutex cv_m;
int i = 0;
void waits()
{
    std::unique_lock<std::mutex> lk(cv_m);
    std::cerr << "Waiting... \n";
    cv.wait(lk, [](){return i == 1;});
    std::cerr << "...finished waiting. i == 1\n";
}
void signals()
{
    std::this_thread::sleep_for(std::chrono::seconds(1));
    std::cerr << "Notifying...\n";
    cv.notify_one();
    std::this_thread::sleep_for(std::chrono::seconds(1));
    i = 1;
    std::cerr << "Notifying again...\n";
    cv.notify_one();
}
int main()
{
    std::thread t1(waits), t2(signals);
    t1.join(); t2.join();
}

Output:

Waiting...
Notifying...
Notifying again...
...finished waiting. i == 1

[edit] See also


notify_all	notifies all waiting threads (public member function)

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std::condition_variable::notify_one

Contents

[edit] Parameters

[edit] Return value

[edit] Exceptions

[edit] Example

[edit] See also