Modern C++ Concurrency: Get the most out of any machine/

...

/

Spinlock vs. Mutex

Spinlock vs. Mutex

It’s very interesting to compare the active waiting of a spinlock with the passive waiting of a mutex. Let's continue our discussing from the previous lesson and make a comparison between these two.

We'll cover the following...

What will happen to the CPU load if the function workOnResource locks the spinlock for 2 seconds (lines 24 - 26)?

Press + to interact
// spinLockSleep.cpp
#include <iostream>
#include <atomic>
#include <thread>
class Spinlock{
  std::atomic_flag flag;
public:
  Spinlock(): flag(ATOMIC_FLAG_INIT){}
  void lock(){
    while( flag.test_and_set() );
  }
  void unlock(){
    flag.clear();
  }
};
Spinlock spin;
void workOnResource(){
  spin.lock();
  std::this_thread::sleep_for(std::chrono::milliseconds(2000));
  spin.unlock();
  std::cout << "Work done" << std::endl;
}
int main(){
  std::thread t(workOnResource);
  std::thread t2(workOnResource);
  t.join();
  t2.join();
}

According to the theory, one of the four cores of PC will be fully utilized, and ...