Re: delete-process bug

[Michaël Cadilhac]

Eli Zaretskii <address@hidden> writes:

>> From: address@hidden (=?iso-8859-1?Q?Micha=EBl?= Cadilhac)
>> Cc: address@hidden,  address@hidden,  address@hidden
>> Date: Mon, 29 May 2006 23:42:39 +0200
>> 
>> I will summarize the whole thing:
>
> Thanks.  I think I understand now.
>
>> AFAICT, both functions are just in a #ifdef subprocesses. But, maybe,
>> in some systems, sigchld_handler is not used albeit compiled.
>> 
>> The question I asked is : do we have to disable the
>> `deleted_process_alist' mechanism in some configuration to avoid that
>> it will be filled but never cleaned ?
>
> Well, as we established, at least on MS-Windows, sigchld_handler _is_
> called, so your fix should work for the Windows build, AFAIU.

So, AFAIU too, if delete_process can be called (protected by #ifdef
subprocesses), sigchld_handler can be too.

Patch updated to remove #ifdef SIGCHLD guards attached.

It addresses all the problems we've seen so far, and seems to work (AFAICT). 

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       29 May 2006 22:26:17 -0000
***************
*** 778,783 ****
--- 778,791 ----
    return proc;
  }
  
+ 
+ /* 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;
+ 
  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
***************
*** 799,810 ****
      }
    else if (XINT (p->infd) >= 0)
      {
!       Fkill_process (process, Qnil);
!       /* Do this now, since remove_process will make sigchld_handler do 
nothing.  */
!       p->status
!       = Fcons (Qsignal, Fcons (make_number (SIGKILL), Qnil));
!       XSETINT (p->tick, ++process_tick);
!       status_notify (p);
      }
    remove_process (process);
    return Qnil;
--- 807,835 ----
      }
    else if (XINT (p->infd) >= 0)
      {
!       Lisp_Object symbol;
! 
!       /* 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));
!       /* If the process has already signaled, remove it from the list.  */
!       if (p->raw_status_new)
!       update_status (p);
!       symbol = p->status;
!       if (CONSP (p->status))
!       symbol = XCAR (p->status);
!       if (EQ (symbol, Qsignal) || EQ (symbol, Qexit))
!       Fdelete (make_fixnum_or_float (p->pid), deleted_pid_list);
!       else
!       {
!         Fkill_process (process, Qnil);
!         /* Do this now, since remove_process will make sigchld_handler do 
nothing.  */
!         p->status
!           = Fcons (Qsignal, Fcons (make_number (SIGKILL), Qnil));
!         XSETINT (p->tick, ++process_tick);
!         status_notify (p);
!       }
      }
    remove_process (process);
    return Qnil;
***************
*** 6373,6378 ****
--- 6398,6412 ----
  
        /* Find the process that signaled us, and record its status.  */
  
+       /* 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;
+       }
+ 
+       /* 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;
--- 6458,6465 ----
            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 ****
--- 6476,6485 ----
            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 ****
--- 6881,6887 ----
    FD_SET (0, &input_wait_mask);
  
    Vprocess_alist = Qnil;
+   deleted_pid_list = Qnil;
    for (i = 0; i < MAXDESC; i++)
      {
        chan_process[i] = Qnil;
***************
*** 6981,6986 ****
--- 7020,7026 ----
    staticpro (&Qlast_nonmenu_event);
  
    staticpro (&Vprocess_alist);
+   staticpro (&deleted_pid_list);
  
    DEFVAR_BOOL ("delete-exited-processes", &delete_exited_processes,
               doc: /* *Non-nil means delete processes immediately when they 
exit.

-- 
 |      Michaël `Micha' Cadilhac   |    Le copillage-collage                |
 |         Epita/LRDE Promo 2007   |       tue le programmeur.              |
 | http://www.lrde.org/~cadilh_m   |           -- Dictons LRDE              |
 `--  -   JID: address@hidden --'                                   -  --'

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