[Asterisk-Dev] waitpid in app_agi.c

[marco.parisotto at virgilio.it]

Hi all,
it's easy to see that each time a dial plan calls an AGI script, a zombie
is created when that AGI script terminates.
 
----------------------------
For example:
 
s,1,answer
s,2,AGI(test.agi)
s,3,hangup
 
where test.agi is a whatever script
 
test.agi:
#!/usr/bin/perl
exit (0);
---------------------------
 
This behavior is due to the fact that Asterisk does not wait ( or waitpid)
for its child.
I fixed this problem in app_agi.c calling fork() twice and letting the init
function become the parent of the second child (which actually executes
the AGI script). This is a non-blocking way for waiting for the child process.
 
--------------------
My app_agi.c:
 
(...)
 
 pid = fork();
 if (pid < 0) {
  ast_log(LOG_WARNING, "Failed to fork(): %s\n", strerror(errno));
  return -1;
 }
 if (!pid) {
  /* first child */
  pid = fork();
         if (pid < 0) {
                 ast_log(LOG_WARNING, "Failed to fork(): %s\n", strerror(errno));
                 return -1;
         }
  if (!pid) {
   /* second child */
   /* Redirect stdin and out, provide enhanced audio channel if desired
*/
   dup2(fromast[0], STDIN_FILENO);
   dup2(toast[1], STDOUT_FILENO);
   if (efd) {
    dup2(audio[0], STDERR_FILENO + 1);
   } else {
    close(STDERR_FILENO + 1);
   }
   /* Close everything but stdin/out/error */
   for (x=STDERR_FILENO + 2;x<1024;x++) 
    close(x);
   /* Execute script */
   execl(script, script, args, (char *)NULL);
   /* Can't use ast_log since FD's are closed */
   fprintf(stderr, "Failed to execute '%s': %s\n", script, strerror(errno));
   exit(1);
  } else 
   exit(0); /* exiting parent of second child = first child */
  
 }
 if (waitpid(pid, NULL, 0) != pid)
   fprintf(stderr, "Failed to wait for first child PID '%d'", pid);
 if (option_verbose > 2) 
  ast_verbose(VERBOSE_PREFIX_3 "Launched AGI Script %s\n", script);
 
(...)

-----------------------
 
Any comment would be appreciated.
Thanks
 
Marco P