From owner-svn-src-head@FreeBSD.ORG  Wed Mar 21 17:41:20 2012
Return-Path: <owner-svn-src-head@FreeBSD.ORG>
Delivered-To: svn-src-head@freebsd.org
Received: from [127.0.0.1] (freefall.freebsd.org [IPv6:2001:4f8:fff6::28])
	by hub.freebsd.org (Postfix) with ESMTP id 528DB1065674;
	Wed, 21 Mar 2012 17:41:20 +0000 (UTC)
	(envelope-from jkim@FreeBSD.org)
From: Jung-uk Kim <jkim@FreeBSD.org>
To: Konstantin Belousov <kostikbel@gmail.com>
Date: Wed, 21 Mar 2012 13:41:03 -0400
User-Agent: KMail/1.6.2
References: <201203202037.q2KKbNfK037014@svn.freebsd.org>
	<20120321100722.GP2358@deviant.kiev.zoral.com.ua>
In-Reply-To: <20120321100722.GP2358@deviant.kiev.zoral.com.ua>
MIME-Version: 1.0
Content-Disposition: inline
Content-Type: text/plain;
  charset="iso-8859-1"
Content-Transfer-Encoding: 7bit
Message-Id: <201203211341.11859.jkim@FreeBSD.org>
Cc: "svn-src-head@freebsd.org" <svn-src-head@freebsd.org>,
	"svn-src-all@freebsd.org" <svn-src-all@freebsd.org>,
	"src-committers@freebsd.org" <src-committers@freebsd.org>
Subject: Re: svn commit: r233249 - head/sys/amd64/acpica
X-BeenThere: svn-src-head@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: SVN commit messages for the src tree for head/-current
	<svn-src-head.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/svn-src-head>,
	<mailto:svn-src-head-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/svn-src-head>
List-Post: <mailto:svn-src-head@freebsd.org>
List-Help: <mailto:svn-src-head-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/svn-src-head>,
	<mailto:svn-src-head-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Wed, 21 Mar 2012 17:41:21 -0000

On Wednesday 21 March 2012 06:07 am, Konstantin Belousov wrote:
> On Tue, Mar 20, 2012 at 08:37:23PM +0000, Jung-uk Kim wrote:
> > Author: jkim
> > Date: Tue Mar 20 20:37:23 2012
> > New Revision: 233249
> > URL: http://svn.freebsd.org/changeset/base/233249
> >
> > Log:
> >   Fix another witness panic.  We cannot enter critical section at
> > all because AcpiEnterSleepState() executes (optional) _GTS method
> > since ACPICA 20120215 (r231844).  To evaluate the method, we need
> > malloc(9), which may sleep.
>
> You papered over the issue, and not fixed it.

Yes, it is a stopgap.

> If sleep may happen, as it is for malloc, you cannot sleep with
> interrupts turned off. This would cause a deadlock at best.

I am well aware of the problem.  In fact, that's why I had to merge 
ACPICA 20120320 rather quickly, which added a new flag to not execute 
_GTS method.  Both _GTS and _BFS are turned off by default.  You can 
control them with a new tunable "debug.acpi.sleep_flags" if you want.  
Please see the updated acpi(4).

Jung-uk Kim