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» SmaugMuds.org » Bugfix Lists » SmaugFUSS Bugfix List » [Bug] DNS resolver code leave...
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[Bug] DNS resolver code leaves zombie processes behind
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Post is unread #1 Feb 17, 2008, 8:01 pm
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Samson
Black Hand
GroupAdministrators
Posts3,644
JoinedJan 1, 2002

Bug: DNS caching code leaves zombie processes behind
Danger: Low - Generally not a problem unless there are tight restrictions on the number of processes allowed to run.
Found by: Zeno
Fixed by: Kasji

---

comm.c

Locate:
/*
 * LAG alarm!							-Thoric
 */
void caught_alarm( int signum )


Above that, add:
int child_exit_status = 0;

static void clean_up_child_process( int signal_number )
{
   /* Clean up the child process. */
   int status;
   wait( &status );

   /* Store its exit status in a global variable. */
   child_exit_status = status;
}


comm.c, game_loop

Locate:
#ifndef WIN32
   signal( SIGPIPE, SIG_IGN );
   signal( SIGALRM, caught_alarm );
#endif


Change to:
#ifndef WIN32
   signal( SIGPIPE, SIG_IGN );
   signal( SIGALRM, caught_alarm );
   signal( SIGCHLD, clean_up_child_process );
#endif


dns.c, process_dns

Locate and remove:
   int status;


Locate and remove:
   /*
    * we don't have to check here, 
    * cos the child is probably dead already. (but out of safety we do)
    * 
    * (later) I found this not to be true. The call to waitpid( ) is
    * necessary, because otherwise the child processes become zombie
    * and keep lingering around... The waitpid( ) removes them.
    */
   if( d->ipid != -1 )
   {
      waitpid( d->ipid, &status, 0 );
      d->ipid = -1;
   }


Apparently despite having protection against hanging zombie processes, they are still possible to generate. This fix more or less just rearranges the order of things to prevent the zombies from happening.
       
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