Locking multiple mutexes

Question

I'm wondering if it's possible to lock multiple mutexes at the same time, like:

 Mutex1.Lock();  {      Mutex2.Lock();      {           // Code locked by mutex 1 and 2.      }      Mutex2.Unlock();       // Code locked by mutex 1.  }  Mutex1.Unlock(); 

It would be very useful for some situations. Thanks.

Answer 1

std::lock seems to exist for this purpose.

Locks the given Lockable objects lock1, lock2, ..., lockn using a deadlock avoidance algorithm to avoid deadlock. The objects are locked by an unspecified series of calls to lock, try_lock, unlock. If a call to lock or unlock results in an exception, unlock is called for any locked objects before rethrowing.

http://en.cppreference.com/w/cpp/thread/lock

Answer 2

C++17 also provides scoped_lock for the specific purpose of locking multiple mutexes that prevents deadlock in a RAII style, similar to lock_guard.

#include<mutex>  std::mutex mtx1, mtx2; void foo() {     std::scoped_lock lck{mtx1, mtx2};     // proceed }