From: michael.cadilhac@lrde.org (Michaël Cadilhac)
Cc: Michael Mauger <mmaug@yahoo.com>, emacs-devel@gnu.org
Subject: Re: delete-process bug
Date: Sun, 28 May 2006 18:01:34 +0200 [thread overview]
Message-ID: <87pshyqgtd.fsf@lrde.org> (raw)
In-Reply-To: 8764jrlewm.fsf@lrde.org
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michael.cadilhac@lrde.org (Michaël Cadilhac) writes:
> Stefan Monnier <monnier@iro.umontreal.ca> writes:
>
>> BTW, did anyone actually test my code to make sure that it does indeed work
>> and fix the problem?
>>
>> Stefan
>
> As far as I tested, it doesn't work and freeze my Emacs. I'll
> investigate today.
I fixed what we discussed here.
I found two bugs in your proposal:
- the list was set to Qnil at the wrong place (wrong init)
- `return' was used in the handler, but it could still have some
process to treat (a continue would have been better but still
wrong).
A patch is attached.
However, the whole thing still doesn't work ; Emacs freezes or prints
this kind of error message:
Error in post-command-hook: (wrong-type-argument listp (nil DEAD . 18764377))
I thought that the race condition could be the following:
- delq makes some change on the list but not all,
- It is interrupted by the handler,
- The handler now has to deal with a malformed list.
It's certainly a bug too, as with the delq I had some Abort in the
handler of the form:
#0 0xb7a45951 in kill () from /lib/libc.so.6
#1 0x080eb75c in abort () at emacs.c:464
#2 0x081536b2 in Fsignal (error_symbol=137610425, data=137557813) at eval.c:1616
#3 0x081402ce in wrong_type_argument (predicate=137622913, value=149282605) at data.c:124
#4 0x0815c175 in Fmember (elt=71112, list=149282605) at fns.c:1468
#5 0x0818577c in sigchld_handler (signo=17) at process.c:6390
Which I think I don't have without, however, it is not the only error,
as with this line deleted, I still have the previous error and
problems. For example, I don't think it's normal for emacs to receive
a SIGPIPE
#0 0xb7ba62b8 in write () from /lib/libpthread.so.0
#1 0x00000002 in ?? ()
#2 0x0810561e in emacs_write (fildes=12, buf=0x8d26178 "!\n", nbyte=12) at sysdep.c:3370
#3 0x08187afb in send_process (proc=150054228, buf=0x8d26178 "!\n", len=2, object=149437363) at process.c:5489
#4 0x08188274 in Fprocess_send_string (process=150054228, string=149437363) at process.c:5643
#5 0x081534cb in Ffuncall (nargs=3, args=0xbfea69b4) at eval.c:2905
... Alas, most of the backtraces only show Emacs blocked in select,
pthread things or wait_for_termination.
If any hacker can help :-)
Maybe it's not the good solution to keep traces of these. The other
possibility (if we don't consider the wait_for_termination solution),
is to store the PID of the synchronous process ; but I'm confused with
compatibilities with DOS and Mac :-/
If we have the PID of the synchronous process, we can explicitly test
it in sigchld_handler.
[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
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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 15:29:27 -0000
***************
*** 778,783 ****
--- 778,792 ----
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
***************
*** 800,805 ****
--- 809,818 ----
else if (XINT (p->infd) >= 0)
{
Fkill_process (process, Qnil);
+ /* No problem storing the pid here, as it is still in Vprocess_alist. */
+ deleted_pid_list = Fcons (make_fixnum_or_float (p->pid),
+ /* GC handled elements set to nil. */
+ Fdelq (Qnil, deleted_pid_list));
/* Do this now, since remove_process will make sigchld_handler do nothing. */
p->status
= Fcons (Qsignal, Fcons (make_number (SIGKILL), Qnil));
***************
*** 6373,6445 ****
/* Find the process that signaled us, and record its status. */
! p = 0;
! for (tail = Vprocess_alist; GC_CONSP (tail); tail = XCDR (tail))
! {
! proc = XCDR (XCAR (tail));
! p = XPROCESS (proc);
! if (GC_EQ (p->childp, Qt) && p->pid == pid)
! break;
p = 0;
! }
! /* Look for an asynchronous process whose pid hasn't been filled
! in yet. */
! if (p == 0)
! for (tail = Vprocess_alist; GC_CONSP (tail); tail = XCDR (tail))
! {
! proc = XCDR (XCAR (tail));
! p = XPROCESS (proc);
! if (p->pid == -1)
! break;
! p = 0;
! }
! /* Change the status of the process that was found. */
! if (p != 0)
! {
! union { int i; WAITTYPE wt; } u;
! int clear_desc_flag = 0;
! XSETINT (p->tick, ++process_tick);
! u.wt = w;
! p->raw_status = u.i;
! p->raw_status_new = 1;
!
! /* If process has terminated, stop waiting for its output. */
! if ((WIFSIGNALED (w) || WIFEXITED (w))
! && XINT (p->infd) >= 0)
! clear_desc_flag = 1;
! /* We use clear_desc_flag to avoid a compiler bug in Microsoft C. */
! if (clear_desc_flag)
! {
! FD_CLR (XINT (p->infd), &input_wait_mask);
! FD_CLR (XINT (p->infd), &non_keyboard_wait_mask);
! }
! /* Tell wait_reading_process_output that it needs to wake up and
! look around. */
! if (input_available_clear_time)
! 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;
! /* Report the status of the synchronous process. */
! if (WIFEXITED (w))
! synch_process_retcode = WRETCODE (w);
! else if (WIFSIGNALED (w))
! synch_process_termsig = WTERMSIG (w);
!
! /* Tell wait_reading_process_output that it needs to wake up and
! look around. */
! if (input_available_clear_time)
! EMACS_SET_SECS_USECS (*input_available_clear_time, 0, 0);
}
/* On some systems, we must return right away.
--- 6386,6466 ----
/* 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);
! else
! {
! /* Otherwise, if it is asynchronous, it is in Vprocess_alist. */
p = 0;
! for (tail = Vprocess_alist; GC_CONSP (tail); tail = XCDR (tail))
! {
! proc = XCDR (XCAR (tail));
! p = XPROCESS (proc);
! if (GC_EQ (p->childp, Qt) && p->pid == pid)
! break;
! p = 0;
! }
! /* Look for an asynchronous process whose pid hasn't been filled
! in yet. */
! if (p == 0)
! for (tail = Vprocess_alist; GC_CONSP (tail); tail = XCDR (tail))
! {
! proc = XCDR (XCAR (tail));
! p = XPROCESS (proc);
! if (p->pid == -1)
! break;
! p = 0;
! }
! /* Change the status of the process that was found. */
! if (p != 0)
! {
! union { int i; WAITTYPE wt; } u;
! int clear_desc_flag = 0;
! XSETINT (p->tick, ++process_tick);
! u.wt = w;
! p->raw_status = u.i;
! p->raw_status_new = 1;
!
! /* If process has terminated, stop waiting for its output. */
! if ((WIFSIGNALED (w) || WIFEXITED (w))
! && XINT (p->infd) >= 0)
! clear_desc_flag = 1;
! /* We use clear_desc_flag to avoid a compiler bug in Microsoft C. */
! if (clear_desc_flag)
! {
! FD_CLR (XINT (p->infd), &input_wait_mask);
! FD_CLR (XINT (p->infd), &non_keyboard_wait_mask);
! }
! /* Tell wait_reading_process_output that it needs to wake up and
! look around. */
! if (input_available_clear_time)
! 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;
! /* Report the status of the synchronous process. */
! if (WIFEXITED (w))
! synch_process_retcode = WRETCODE (w);
! else if (WIFSIGNALED (w))
! synch_process_termsig = WTERMSIG (w);
!
! /* Tell wait_reading_process_output that it needs to wake up and
! look around. */
! if (input_available_clear_time)
! EMACS_SET_SECS_USECS (*input_available_clear_time, 0, 0);
! }
}
/* On some systems, we must return right away.
***************
*** 6843,6848 ****
--- 6864,6870 ----
FD_SET (0, &input_wait_mask);
Vprocess_alist = Qnil;
+ deleted_pid_list = Qnil;
for (i = 0; i < MAXDESC; i++)
{
chan_process[i] = Qnil;
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--
| Michaël `Micha' Cadilhac | Mieux vaut se taire |
| Epita/LRDE Promo 2007 | Que de parler trop fort. |
| http://www.lrde.org/~cadilh_m | -- As de trèfle |
`-- - JID: micha@amessage.be --' - --'
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next prev parent reply other threads:[~2006-05-28 16:01 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-04-24 19:36 Ispell loads dict twice Michaël Cadilhac
2006-04-26 10:14 ` Agustin Martin
2006-04-26 21:58 ` Michaël Cadilhac
2006-05-23 18:26 ` Michaël Cadilhac
2006-05-24 11:28 ` Agustin Martin
2006-05-25 10:57 ` delete-process bug (was: Ispell loads dict twice.) Michaël Cadilhac
2006-05-25 12:19 ` Agustin Martin
2006-05-25 14:55 ` delete-process bug Stefan Monnier
2006-05-25 14:59 ` David Kastrup
2006-05-25 15:17 ` Michaël Cadilhac
2006-05-25 15:26 ` David Kastrup
2006-05-25 19:40 ` Stefan Monnier
2006-05-25 23:51 ` Kim F. Storm
2006-05-26 4:49 ` Richard Stallman
2006-05-26 13:03 ` Stefan Monnier
2006-05-26 2:22 ` Richard Stallman
2006-05-26 11:29 ` Michaël Cadilhac
2006-05-27 3:36 ` Richard Stallman
2006-05-26 13:10 ` Stefan Monnier
2006-05-26 17:27 ` Michael Mauger
2006-05-27 9:19 ` Michaël Cadilhac
2006-05-27 14:16 ` Stefan Monnier
2006-05-27 14:29 ` Michaël Cadilhac
2006-05-28 16:01 ` Michaël Cadilhac [this message]
2006-05-28 18:00 ` Stefan Monnier
2006-05-28 18:32 ` Michaël Cadilhac
2006-05-28 19:48 ` Stefan Monnier
2006-05-28 20:26 ` Michaël Cadilhac
2006-05-28 21:15 ` Kim F. Storm
2006-05-28 21:36 ` Michaël Cadilhac
2006-05-28 23:54 ` Stefan Monnier
2006-05-29 11:39 ` Michaël Cadilhac
2006-05-29 8:22 ` Kim F. Storm
2006-05-29 8:50 ` David Kastrup
2006-05-29 19:04 ` Eli Zaretskii
2006-05-29 19:27 ` Eli Zaretskii
2006-05-29 21:42 ` Kim F. Storm
2006-05-29 22:08 ` Eli Zaretskii
2006-05-29 3:32 ` Eli Zaretskii
2006-05-29 8:14 ` Kim F. Storm
2006-05-29 10:59 ` Michaël Cadilhac
2006-05-29 19:25 ` Eli Zaretskii
2006-05-29 20:04 ` Michaël Cadilhac
2006-05-29 21:24 ` Eli Zaretskii
2006-05-29 21:42 ` Michaël Cadilhac
2006-05-29 22:11 ` Eli Zaretskii
2006-05-29 22:32 ` Michaël Cadilhac
2006-05-30 12:11 ` Kim F. Storm
2006-05-30 12:42 ` Michaël Cadilhac
2006-05-30 14:26 ` Kim F. Storm
2006-05-30 15:13 ` Michaël Cadilhac
2006-06-01 14:06 ` Kim F. Storm
2006-06-01 14:20 ` Michaël Cadilhac
2006-06-01 14:29 ` Kim F. Storm
2006-06-01 16:05 ` Michaël Cadilhac
2006-06-02 7:46 ` Kim F. Storm
2006-06-01 16:41 ` Agustin Martin
2006-06-01 16:55 ` Michaël Cadilhac
2006-05-29 23:07 ` Agustin Martin
2006-05-25 23:52 ` delete-process bug (was: Ispell loads dict twice.) Kim F. Storm
2006-06-06 20:45 ` Ispell loads dict twice Michaël Cadilhac
2006-06-09 13:02 ` Kim F. Storm
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