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Showing content from https://stackoverflow.com/questions/5454746/pthread-mutex-lock-unlock-by-different-threads below:

linux - Pthread Mutex lock unlock by different threads

A Naive question ..

I read before saying - "A MUTEX has to be unlocked only by the thread that locked it."

But I have written a program where THREAD1 locks mutexVar and goes for a sleep. Then THREAD2 can directly unlock mutexVar do some operations and return.

==> I know everyone say why I am doing so ?? But my question is - Is this a right behaviour of MUTEX ??

==> Adding the sample code

void *functionC()
{
   pthread_mutex_lock( &mutex1 );
   counter++;
   sleep(10);
   printf("Thread01: Counter value: %d\n",counter);
   pthread_mutex_unlock( &mutex1 );
}

void *functionD()
{
   pthread_mutex_unlock( &mutex1 );
   pthread_mutex_lock( &mutex1 );
   counter=10;
   printf("Counter value: %d\n",counter);
}

int main()
{
   int rc1, rc2;
   pthread_t thread1, thread2;

   if(pthread_mutex_init(&mutex1, NULL))
   printf("Error while using pthread_mutex_init\n");

   if( (rc1=pthread_create( &thread1, NULL, &functionC, NULL)) )
   {   
      printf("Thread creation failed: %d\n", rc1);
   }   

   if( (rc2=pthread_create( &thread2, NULL, &functionD, NULL)) )
   {   
      printf("Thread creation failed: %d\n", rc2);
   } 

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