From owner-freebsd-current@FreeBSD.ORG  Sat Jun 30 14:41:43 2007
Return-Path: <owner-freebsd-current@FreeBSD.ORG>
X-Original-To: freebsd-current@freebsd.org
Delivered-To: freebsd-current@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52])
	by hub.freebsd.org (Postfix) with ESMTP id B44BD16A473
	for <freebsd-current@freebsd.org>; Sat, 30 Jun 2007 14:41:43 +0000 (UTC)
	(envelope-from michiel@boland.org)
Received: from neerbosch.nijmegen.internl.net (neerbosch.nijmegen.internl.net
	[217.149.193.38])
	by mx1.freebsd.org (Postfix) with ESMTP id 5318A13C4C8
	for <freebsd-current@freebsd.org>; Sat, 30 Jun 2007 14:41:43 +0000 (UTC)
	(envelope-from michiel@boland.org)
Received: from neerbosch.nijmegen.internl.net by neerbosch.nijmegen.internl.net
	via neerbosch.nijmegen.internl.net [217.149.193.38] with ESMTP for
	<freebsd-current@freebsd.org>
	id l5UEfgBS000300 (8.13.4/1.4); Sat, 30 Jun 2007 16:41:42 +0200 (MEST)
Received: from localhost by neerbosch.nijmegen.internl.net
	via mboland@localhost with ESMTP for <freebsd-current@freebsd.org>
	id l5UEfgpM000297 (8.13.4/2.02); Sat, 30 Jun 2007 16:41:42 +0200 (MEST)
X-Authentication-Warning: neerbosch.nijmegen.internl.net: mboland owned
	process doing -bs
Date: Sat, 30 Jun 2007 16:41:42 +0200 (MEST)
From: Michiel Boland <michiel@boland.org>
To: freebsd-current@freebsd.org
Message-ID: <Pine.GSO.4.64.0706301632320.29496@neerbosch.nijmegen.internl.net>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed
Subject: tcsh hangs in sigsuspend
X-BeenThere: freebsd-current@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Discussions about the use of FreeBSD-current
	<freebsd-current.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>, 
	<mailto:freebsd-current-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-current>
List-Post: <mailto:freebsd-current@freebsd.org>
List-Help: <mailto:freebsd-current-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>,
	<mailto:freebsd-current-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Sat, 30 Jun 2007 14:41:43 -0000

Hi. I can no longer do simple things like

  kill `cat pidfile`

in tcsh.

After some debugging I noticed that tcsh hangs in sigsuspend in line 512 
of sh.proc.c. So I guess it (tcsh) executed 'cat pidfile', and now waits 
for the process to terminate. But unless I'm not looking properly, there 
appears to be a race condition here. Tcsh blocks the SIGCHLD signal 
*after* it forks the child, not before. So the child could wel have exited 
between the call to fork and the call to sigprocmask. In that case, would 
not the sigsuspend hang forever?

Also, I noticed that gdb gets very confused if I try to debug tcsh with 
a backticked command like the one above. (I guess this is the same as 
bin/112408)

Cheers
Michiel