Thread Locking in C#

Thread locking is used to ensure that only one thread can enter particular sections of code at a time…

Main exclusive locking constructs are lock , Mutex and nonexclusive locking constructs is semaphores.

class ThreadUnsafe
{
  static int _val1 = 1, _val2 = 1;

  static void Go()
  {
    if (_val2 != 0) Console.WriteLine (_val1 / _val2);
    _val2 = 0;
  }
}

This class is not thread-safe: if Go was called by two threads simultaneously, it would be possible to get a division-by-zero error, because _val2 could be set to zero in one thread right as the other thread was in between executing the if statement and Console.WriteLine.

Here’s how lock can fix the problem:

class ThreadSafe
{
  static readonly object _locker = new object();
  static int _val1, _val2;

  static void Go()
  {
    lock (<span style="color: #ff6600;"><strong>_locker</strong></span>)
    {
      if (_val2 != 0) Console.WriteLine (_val1 / _val2);
      _val2 = 0;
    }
  }
}

Only one thread can lock the synchronizing object (in this case, _locker) at a time, and any contending threads are blocked until the lock is released. If more than one thread contends the lock, they are queued on a “ready queue” and granted the lock on a first-come, first-served basis

 

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