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Showing content from https://cplusplus.com/mutex::try_lock below:

public member function

<mutex>

Lock mutex if not locked

• If the mutex isn't currently locked by any thread, the calling thread locks it (from this point, and until its member unlock is called, the thread owns the mutex).
• If the mutex is currently locked by another thread, the function fails and returns false, without blocking (the calling thread continues its execution).
• If the mutex is currently locked by the same thread calling this function, it produces a deadlock (with undefined behavior). See recursive_mutex for a mutex type that allows multiple locks from the same thread.

All lock and unlock operations on the mutex follow a single total order, with all visible effects synchronized between the lock operations and previous unlock operations on the same object.

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// mutex::try_lock example
#include <iostream>       // std::cout
#include <thread>         // std::thread
#include <mutex>          // std::mutex

volatile int counter (0); // non-atomic counter
std::mutex mtx;           // locks access to counter

void attempt_10k_increases () {
  for (int i=0; i<10000; ++i) {
    if (mtx.try_lock()) {   // only increase if currently not locked:
      ++counter;
      mtx.unlock();
    }
  }
}

int main ()
{
  std::thread threads[10];
  // spawn 10 threads:
  for (int i=0; i<10; ++i)
    threads[i] = std::thread(attempt_10k_increases);

  for (auto& th : threads) th.join();
  std::cout << counter << " successful increases of the counter.\n";

  return 0;
}

80957 successful increases of the counter.

mutex::lock

Lock mutex (public member function)

mutex::unlock

Unlock mutex (public member function)

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