43 lines
1.0 KiB
C++
43 lines
1.0 KiB
C++
#include <iostream>
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#include <condition_variable>
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#include <thread>
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#include <chrono>
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std::condition_variable cv;
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std::mutex cv_m; // 此互斥用于三个目的：
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// 1) 同步到 i 的访问
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// 2) 同步到 std::cerr 的访问
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// 3) 为条件变量 cv
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int i = 0;
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void waits() {
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std::unique_lock<std::mutex> lk(cv_m);
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std::cerr << "Waiting... \n";
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cv.wait(lk, []{return i == 1;});
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std::cerr << "...finished waiting. i == 1\n";
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}
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void signals() {
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std::this_thread::sleep_for(std::chrono::seconds(1));
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{
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std::lock_guard<std::mutex> lk(cv_m);
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std::cerr << "Notifying...\n";
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}
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cv.notify_all();
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std::this_thread::sleep_for(std::chrono::seconds(1));
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{
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std::lock_guard<std::mutex> lk(cv_m);
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i = 1;
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std::cerr << "Notifying again...\n";
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}
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cv.notify_all();
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}
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int main() {
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std::thread t1(waits), t2(waits), t3(waits), t4(signals);
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t1.join();
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t2.join();
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t3.join();
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t4.join();
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} |