Subj : thread Cleanup handler is not called
To   : comp.programming.threads
From : neelapune
Date : Tue Feb 15 2005 10:46 pm

Hi,
    I have been facing the bizaar problem with pthreads in linux. I
wanted to invoke my cleanup handler whenever I cancel the thread
created. Please refer to the code attached. In my thread routine
function "void *thread_routine(void *arg)", there is a while loop
inside which i have used a printf, when this printf is a part of the
thread function, during thread cancellation my handler is called i.e
"void cleanup_handler(void *arg)". Now when i comment the printf and
re compile the program(gcc -lpthread sample.c) and run it, during
thread cancellation my cleanup handler is not called!!!!.

   I have failed to understand this logic. Is there any logical or
conceptual flaw in my program. I see that printf is not a reentrant or
thread safe function, however i am not able to appreciate how that
would have anything to do with my function not being called.

  Any help is greatly appreciated..


Thanks

Neela
  

----------------------------sample.c------------------------------------------

#include <pthread.h>
#include <stdio.h>
#include <signal.h>
 
void cleanup_handler(void *arg)
{
  printf("Clean up handler is called\n");
  return;
}
 
void *thread_routine(void *arg)
{
  pthread_cleanup_push(cleanup_handler,0);
  int i = 0;
  while(1)
    {
      i++;
 =====>>> printf("Hai\n");  <<<==== 
 /*
  * If i comment out the above printf cleanup handler is not called
  * else cleanup handler is called
  */
      pthread_testcancel();
    }
  pthread_cleanup_pop(1);
  pthread_exit(0);
}
 
int main(int argc, char *argv[])
{
  pthread_t tid;
  if (pthread_create(&tid,NULL,thread_routine,0) != 0)
    {
      printf("Thread Creation Failed\n");
      return 0;
    }
  sleep(5);
  if(pthread_cancel(tid)!=0)
    {
      printf("Thread Cancelation Failed\n");
      return 0;
    }
  return 0;
}
-------------------------------------Code
Ends---------------------------------

.