c - Thread concurrency in linux -

i beginner so, please let me know if question not clear.

i using 2 threads example , b. , have global variable 'p'. thread while looping , incrementing value of 'p'.at same time b trying set 'p' other value(both 2 different thread functions).

if using mutex synchronizations, , thread mutex , incrementation 'p' in while loop,but not release mutex. question if thread doesn’t release mutex can thread b access variable 'p'??

edit thread b protected accses 'p' using mutex.

if thread lock using pthread_mutex_lock(), , doesn’t release , happen if same thread(a) try access lock again(remember thread while looping) example

   while(1)         {             pthread_mutex_lock(&mutex);             p = 10;          } 

is there problem code if mutex never released?

simple example of statically initialized mutex

#include <pthread.h> #include <stdio.h> #include <stdlib.h>  static int p = 0; static pthread_mutex_t locker = pthread_mutex_initializer;  static void * threadfunc(void *arg) {   int err;   err = pthread_mutex_lock(&locker);   if (err != 0){     perror("pthread_mutex_lock failed");     exit(1);   }   p++;   err = pthread_mutex_unlock(&locker);   if (err != 0){     perror("pthread_mutex_unlock failed");     exit(1);   }   return null; }  int main(int argc, char *argv[]) {   pthread_t a, b;   pthread_create(&a, null, threadfunc, null);   pthread_create(&b, null, threadfunc, null);   pthread_join(a, null);   pthread_join(b, null);   printf("p = %d\n", p);   return 0; } 

error checking in main omitted brevity should used. if not release mutex program never finish, thread b never lock.