Re: delete-process bug

[michael.cadilhac@lrde.org (Michaël Cadilhac)]

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storm@cua.dk (Kim F. Storm) writes:

> michael.cadilhac@lrde.org (Michaël Cadilhac) writes:
>
>> (Final ?) patch attached.
>
> Looks good to me!
>
> I wonder whether the pid should be added to deleted_pid_list if SIGCHLD is
> not defined?  In that case, it would be a memory leak...

Oh, hmm... About memory leaks hrm...

In fact, there is already a configuration that would lead to the non
deletion of the PID from the list:

- Call to delete_process,
- Interrupted by a signal before inserting  in deleted_processes_list ,
- Deletion from  process_alist,
- Then delete_process continues by... inserting the dead PID in the
    deleted_processes_list.

I forgot to tell about it in my previous post. Sorry.

Any idea for fixing this ? Putting the insertion in
deleted_processes_list BEFORE the Kill would limit this leak, but not
completely avoid it.


> But I also wonder if any of the async process stuff actually works
> without SIGCHLD ?!?   Are there any systems which support async processes
> but don't have SIGCHLD?

Indeed, I  don't know any system  in which SIGCHLD is  not defined and
that  can  use sub  processes  (are  we  talking about  a  one-process
system ?!).

But it would be cleaner, indeed, to define the whole thing iff SIGCHLD
is defined.

I modified the patch for that (including in sigchld_handler and so
because the list is not defined if SIGCHLD is not), and to make the
insertion in deleted_processes_list before the kill.


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Index: src/process.c
===================================================================
RCS file: /sources/emacs/emacs/src/process.c,v
retrieving revision 1.481
diff -c -r1.481 process.c
*** src/process.c	8 May 2006 05:19:42 -0000	1.481
--- src/process.c	28 May 2006 21:35:32 -0000
***************
*** 778,783 ****
--- 778,793 ----
    return proc;
  }
  
+ 
+ #ifdef SIGCHLD
+ /* Fdelete_process promises to immediately forget about the process, but in
+    reality, Emacs needs to remember those processes until they have been
+    treated by sigchld_handler; otherwise this handler would consider the
+    process as being synchronous and say that the synchronous process is
+    dead.  */
+ static Lisp_Object deleted_pid_list;
+ #endif
+ 
  DEFUN ("delete-process", Fdelete_process, Sdelete_process, 1, 1, 0,
         doc: /* Delete PROCESS: kill it and forget about it immediately.
  PROCESS may be a process, a buffer, the name of a process or buffer, or
***************
*** 799,804 ****
--- 809,820 ----
      }
    else if (XINT (p->infd) >= 0)
      {
+ #ifdef SIGCHLD
+       /* No problem storing the pid here, as it is still in Vprocess_alist.  */
+       deleted_pid_list = Fcons (make_fixnum_or_float (p->pid),
+ 				/* GC treated elements set to nil.  */
+ 				Fdelq (Qnil, deleted_pid_list));
+ #end
        Fkill_process (process, Qnil);
        /* Do this now, since remove_process will make sigchld_handler do nothing.  */
        p->status
***************
*** 6373,6378 ****
--- 6389,6405 ----
  
        /* Find the process that signaled us, and record its status.  */
  
+ #ifdef SIGCHLD
+       /* The process can have been deleted by Fdelete_process.  */
+       tail = Fmember (make_fixnum_or_float (pid), deleted_pid_list);
+       if (!NILP (tail))
+ 	{
+ 	  Fsetcar (tail, Qnil);
+ 	  goto sigchld_end_of_loop;
+ 	}
+ #endif
+ 
+       /* Otherwise, if it is asynchronous, it is in Vprocess_alist.  */
        p = 0;
        for (tail = Vprocess_alist; GC_CONSP (tail); tail = XCDR (tail))
  	{
***************
*** 6424,6431 ****
  	    EMACS_SET_SECS_USECS (*input_available_clear_time, 0, 0);
  	}
  
! 	/* There was no asynchronous process found for that id.  Check
! 	   if we have a synchronous process.  */
        else
  	{
  	  synch_process_alive = 0;
--- 6451,6458 ----
  	    EMACS_SET_SECS_USECS (*input_available_clear_time, 0, 0);
  	}
  
!       /* There was no asynchronous process found for that pid: we have
! 	 a synchronous process.  */
        else
  	{
  	  synch_process_alive = 0;
***************
*** 6442,6447 ****
--- 6469,6478 ----
  	    EMACS_SET_SECS_USECS (*input_available_clear_time, 0, 0);
  	}
  
+ 
+     sigchld_end_of_loop:
+       ;
+ 
        /* On some systems, we must return right away.
  	 If any more processes want to signal us, we will
  	 get another signal.
***************
*** 6843,6848 ****
--- 6874,6882 ----
    FD_SET (0, &input_wait_mask);
  
    Vprocess_alist = Qnil;
+ #ifdef SIGCHLD
+   deleted_pid_list = Qnil;
+ #endif
    for (i = 0; i < MAXDESC; i++)
      {
        chan_process[i] = Qnil;
***************
*** 6981,6986 ****
--- 7015,7023 ----
    staticpro (&Qlast_nonmenu_event);
  
    staticpro (&Vprocess_alist);
+ #ifdef SIGCHLD
+   staticpro (&deleted_pid_list);
+ #endif
  
    DEFVAR_BOOL ("delete-exited-processes", &delete_exited_processes,
  	       doc: /* *Non-nil means delete processes immediately when they exit.

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-- 
 |      Michaël `Micha' Cadilhac   |   Pour les 35-40 ans, l'humour         |
 |         Epita/LRDE Promo 2007   |        c'est une plus-value.           |
 | http://www.lrde.org/~cadilh_m   |           -- Guillaume L.              |
 `--  -   JID: micha@amessage.be --'                                   -  --'

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