unable to use a function to crate a joinable thread Post: 302518209

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Top Forums Programming unable to use a function to crate a joinable thread Post 302518209 by sehang on Friday 29th of April 2011 12:02:13 AM

04-29-2011

Registered User

unable to use a function to crate a joinable thread

In my program, threads may be created when some events trigger. So I can't create threads on initialization.

Theremore,I write a createThread() function to create thread. However, it is blocking at first call and don't run anymore? why?

Code:

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

void *BusyWork(void *t)
{
   int i = 0;
   long tid;
   double result=0.0;
   tid = (long)t;
   printf("Thread %ld starting...\n",tid);
   while ( 1 ) {
      result = result + sin(i) * tan(i);
      i++;
   }
   printf("Thread %ld done. Result = %e\n",tid, result);
   pthread_exit((void*) t);
}


void createThread () {
  int rc;
  void *status;
  pthread_attr_t attr;
  pthread_t thread;
  pthread_attr_init(&attr);
  pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE);
  rc = pthread_create(&thread, &attr, BusyWork, (void *)0); 
  if (rc) {
    printf("ERROR; return code from pthread_create() is %d\n", rc);
    exit(-1);
   }
    pthread_attr_destroy(&attr);
    rc = pthread_join(thread, &status);
    if (rc) {
       printf("ERROR; return code from pthread_join() is %d\n", rc);
       exit(-1);
    }
    printf("Main: completed join with thread %d having a status of %ld\n",0,(long)status);
}

int main (int argc, char *argv[])
{
  createThread();  // <- Blocking here
  createThread();  
  printf("Main: program completed. Exiting.\n");
  pthread_exit(NULL);
}

Thanks for your help!

sehang

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pthread_create

PTHREAD_CREATE(3)					     Library Functions Manual						 PTHREAD_CREATE(3)

NAME

       pthread_create - create a new thread

SYNOPSIS

       #include <pthread.h>

       int pthread_create(pthread_t * thread, pthread_attr_t * attr, void * (*start_routine)(void *), void * arg);

DESCRIPTION

       pthread_create  creates	a  new	thread	of control that executes concurrently with the calling thread. The new thread applies the function
       start_routine passing it arg as first argument. The new thread terminates either explicitly, by calling pthread_exit(3), or implicitly,	by
       returning  from the start_routine function. The latter case is equivalent to calling pthread_exit(3) with the result returned by start_rou-
       tine as exit code.

       The attr argument specifies thread attributes to be applied to the new thread. See pthread_attr_init(3)	for  a	complete  list	of  thread
       attributes.  The  attr  argument can also be NULL, in which case default attributes are used: the created thread is joinable (not detached)
       and has default (non real-time) scheduling policy.

RETURN VALUE

       On success, the identifier of the newly created thread is stored in the location pointed by the thread argument, and a 0  is  returned.	On
       error, a non-zero error code is returned.

ERRORS

       EAGAIN not enough system resources to create a process for the new thread.

       EAGAIN more than PTHREAD_THREADS_MAX threads are already active.

AUTHOR

       Xavier Leroy <Xavier.Leroy@inria.fr>

SEE ALSO

       pthread_exit(3), pthread_join(3), pthread_detach(3), pthread_attr_init(3).

								   LinuxThreads 						 PTHREAD_CREATE(3)

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