Subj : Re: Problem with system() calls in a multithreaded program on HPUX 11
To   : comp.programming.threads,comp.sys.hp.hpux
From : maheshkumarjha
Date : Sun Feb 13 2005 11:09 pm

ptjm@interlog.com (Patrick TJ McPhee) wrote in message news:<37a1suF55hncsU2@uni-berlin.de>...
> In article <m3mzub6rjq.fsf@salmon.parasoft.com>,
> Paul Pluzhnikov  <ppluzhnikov-nsp@charter.net> wrote:
> % maheshkumarjha@gmail.com (Mahesh Kumar) writes:
> % 
> % > 	I am porting a multithreaded program to HPUX 11 from Solaris, in
> % > which threads make calls to system() functions.
> % 
> % This is extremely bad idea (TM).
> % 
> % Writing multithreaded programs that fork() correctly requires
> % careful use of pthread_atfork handlers for every possible lock used,
> % both in your code and in every library you link against.
> 
> I'd say that atfork handlers are largely useless. Whatever you do with
> mutexes, for instance, is irrelevant because the child process isn't
> allowed to lock or unlock them anyway. execing a new process image is
> allowed, though. system() is problematic, but the problem is with
> waiting for the child process to finish, rather than with forking and
> execing.

Well, just to make sure that there was no problem with fork and wait,
I tried replacing system() function call with following,

int my_system (char *command) {
   int status;

   if (command == 0)
       return 1;
   pid_t pid = fork();
   if (pid == -1)
       return -1;
   if (pid == 0) {
       char *argv[4];
       argv[0] = "sh";
       argv[1] = "-c";
       argv[2] = command;
       argv[3] = NULL;
       execve("/bin/sh", argv, environ);
       exit(127);
   }
   do {
       if (waitpid(pid, &status, 0) == -1) {
	   if (errno != EINTR)
	       return -1;
       } else
	   return status;
   } while(1);
}

But still it hanged when I tried to run it for 6 threads. (I already
said number of threads is not consistent.) The only difference being
that there were no <defunct> processes this time.

Can anyone suggest a possible reason for still hanging? 

Thanks and regards.
Mahesh Kumar

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