1. The difference between the semaphores provided by the operating system
1. The difference between the semaphores provided by the operating system
2. The semaphores provided by c++20 can only be used for thread synchronization between the same process
Two, c++20 semaphore
A semaphore is a lightweight synchronization primitive used to restrict concurrent access to shared resources. Semaphores can be more efficient than condition variables when both can be used.
| project | Value |
|---|---|
| counting_semaphore(C++20) | counting_semaphore(C++20) |
| binary_semaphore(C++20) | binary_semaphore(C++20) |
1. Environment configuration:
a. Defined in the header file
b. Visual studio is upgraded to 2019
c. Turn on the switch of c++20 support
2. Example of use
#include <iostream>
#include <semaphore>
#include <thread>
using namespace std;
std::counting_semaphore<3> csem(0);
binary_semaphore bsem(0);
// semaphore release = condition_variable notify
// semaphore acquire = condition_variable wait
void task()
{
cout << "task:ready to recv signal \n";
csem.acquire();
cout << "task:acquire end\n";
}
int main()
{
thread t0(task);
thread t1(task);
thread t2(task);
thread t3(task);
thread t4(task);
cout << "main:ready to signal :release\n";
csem.release(3);
cout << "main: signal end\n";
t0.join();
t1.join();
t2.join();
t3.join();
t4.join();
}
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