From owner-freebsd-current@FreeBSD.ORG  Mon May 28 21:06:38 2007
Return-Path: <owner-freebsd-current@FreeBSD.ORG>
X-Original-To: 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 E1D9F16A47C
	for <current@freebsd.org>; Mon, 28 May 2007 21:06:38 +0000 (UTC)
	(envelope-from asmrookie@gmail.com)
Received: from ug-out-1314.google.com (ug-out-1314.google.com [66.249.92.171])
	by mx1.freebsd.org (Postfix) with ESMTP id 31E9813C44B
	for <current@freebsd.org>; Mon, 28 May 2007 21:06:37 +0000 (UTC)
	(envelope-from asmrookie@gmail.com)
Received: by ug-out-1314.google.com with SMTP id u2so984611uge
	for <current@freebsd.org>; Mon, 28 May 2007 14:06:37 -0700 (PDT)
DKIM-Signature: a=rsa-sha1; c=relaxed/relaxed; d=gmail.com; s=beta;
	h=domainkey-signature:received:received:message-id:date:from:reply-to:user-agent:mime-version:to:cc:subject:references:in-reply-to:content-type:content-transfer-encoding:sender;
	b=QJ1ayBFBkJkT/60eR0buCLOq7ME8nw8iyXqZmYpsWldWs7JYO57jH3vQw7YbLstUhUt/6xe9uLUxUJG9Hpu8zQC9vJIXbRU6ozYyQwaPTh1VxS9qA8ZHzh0VdihWpXxCi7SUt/zI1G1AWQg/7LGUhVsvyBy08OkxtTAud9tw9dc=
DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta;
	h=received:message-id:date:from:reply-to:user-agent:mime-version:to:cc:subject:references:in-reply-to:content-type:content-transfer-encoding:sender;
	b=muCn6p1Jks8lZzA1EFmyVfWSqxhfOWvyS1gcPvycn24G67XpCh4hmAGn2g5wJHwBLsPaPJk90uYtokVqA2L9oERinwMqFM1AubFabO4x76jWrBj8WMtw2dq3fFR5Dk59Al3UWdENC8t05XhrmM8uqquasAGlxd9d+FRmZ8dKEKU=
Received: by 10.67.117.18 with SMTP id u18mr5528705ugm.1180386397026;
	Mon, 28 May 2007 14:06:37 -0700 (PDT)
Received: from ?151.75.216.62? ( [151.75.216.62])
	by mx.google.com with ESMTP id a1sm6186940ugf.2007.05.28.14.06.35;
	Mon, 28 May 2007 14:06:36 -0700 (PDT)
Message-ID: <465B4450.90800@FreeBSD.org>
Date: Mon, 28 May 2007 23:06:24 +0200
From: Attilio Rao <attilio@FreeBSD.org>
User-Agent: Thunderbird 1.5 (X11/20060526)
MIME-Version: 1.0
To: Tor Egge <Tor.Egge@cvsup.no.freebsd.org>
References: <1180138048.94117.17.camel@shumai.marcuscom.com>	<465780A3.8040603@FreeBSD.org>	<1180140483.94117.24.camel@shumai.marcuscom.com>
	<20070528.162023.41711345.Tor.Egge@cvsup.no.freebsd.org>
In-Reply-To: <20070528.162023.41711345.Tor.Egge@cvsup.no.freebsd.org>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Sender: Attilio Rao <asmrookie@gmail.com>
Cc: jroberson@chesapeake.net, current@freebsd.org
Subject: Re: Panic on -CURRENT after LDT changes
X-BeenThere: freebsd-current@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
Reply-To: attilio@FreeBSD.org
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: Mon, 28 May 2007 21:06:39 -0000

Tor Egge wrote:
> 
> Finally, I found that i386_ldt_grow() called smp_rendezvous() without
> temporarily unlocking dt_lock.  That caused a deadlock.  Adding a temporary
> unlock of dt_lock seems to solve the problem for me.

Effectively, there is the need to release the dt_lock before to call 
smp_rendezvous() beacause other threads running on other CPUs will 
contest on this lock and it will cause a deadlock (since their 
curthreads don't hold the lock).
I think that mantaining the current locking requirements for 
i386_ldt_grow() is still good, since, for how it is used, this is the 
lighter approach. I will add release/unrelease around smp_rendezvous() too.

Thanks for the catch,
Attilio