Mutex unlock from different thread?

Question

There are two threads one takes lock and execute infinite loop. When ever other thread start execution before trying to take lock it unlocks the mutex.

Its a wrong behavior, how can I prevent this.

#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>

pthread_t callThd_one, callThd_two;
pthread_mutex_t mutexsum;

void *thread_one(void *arg)
{
   pthread_mutex_lock (&mutexsum);
   while(!sleep(1))
       printf("\n In thread One \n");

   pthread_mutex_unlock (&mutexsum);
   pthread_exit((void*) 0);
}

void *thread_two(void *arg)
{
   pthread_mutex_unlock (&mutexsum);
   //pthread_mutex_lock (&mutexsum);
   while(!sleep(1))
       printf("\n In thread two \n");

   pthread_mutex_unlock (&mutexsum);
   pthread_exit((void*) 0);
}

int main (int argc, char *argv[])
{
   void *status;
   pthread_attr_t attr;

   pthread_mutex_init(&mutexsum, NULL);

   pthread_attr_init(&attr);
   pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE);

   pthread_create(&callThd_one, &attr, thread_one, NULL);
   pthread_create(&callThd_two, &attr, thread_two, NULL);

   pthread_attr_destroy(&attr);

   pthread_join(callThd_one, &status);
   pthread_join(callThd_two, &status);

   pthread_mutex_destroy(&mutexsum);
   pthread_exit(NULL);
}

Is there any way to sure that mutex should be unlock only by the thread which took lock.

Answer 1

This is incorrect way of mutex handling. This problem can be solved two ways

1. instead trying pthread_mutex_unlock and pthread_mutex_lock one should use pthread_mutex_trylock to avoid deadlock scenarios
2. if want to continue with same code use error checking mutex rather default.