From owner-freebsd-current@FreeBSD.ORG  Fri Sep 20 15:27:43 2013
Return-Path: <owner-freebsd-current@FreeBSD.ORG>
Delivered-To: freebsd-current@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115])
 (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits))
 (No client certificate requested)
 by hub.freebsd.org (Postfix) with ESMTP id D1B33D7;
 Fri, 20 Sep 2013 15:27:43 +0000 (UTC) (envelope-from jhb@freebsd.org)
Received: from bigwig.baldwin.cx (bigwig.baldwin.cx [IPv6:2001:470:1f11:75::1])
 (using TLSv1 with cipher ADH-CAMELLIA256-SHA (256/256 bits))
 (No client certificate requested)
 by mx1.freebsd.org (Postfix) with ESMTPS id AAB632E38;
 Fri, 20 Sep 2013 15:27:43 +0000 (UTC)
Received: from jhbbsd.localnet (unknown [209.249.190.124])
 by bigwig.baldwin.cx (Postfix) with ESMTPSA id ADDE8B979;
 Fri, 20 Sep 2013 11:27:42 -0400 (EDT)
From: John Baldwin <jhb@freebsd.org>
To: Gleb Smirnoff <glebius@freebsd.org>
Subject: Re: ipmi patch for review
Date: Fri, 20 Sep 2013 10:02:53 -0400
User-Agent: KMail/1.13.5 (FreeBSD/8.4-CBSD-20130906; KDE/4.5.5; amd64; ; )
References: <20130917102110.GK4574@glebius.int.ru>
 <201309191504.46986.jhb@freebsd.org> <20130920054452.GB4574@glebius.int.ru>
In-Reply-To: <20130920054452.GB4574@glebius.int.ru>
MIME-Version: 1.0
Content-Type: Text/Plain;
  charset="iso-8859-1"
Content-Transfer-Encoding: 7bit
Message-Id: <201309201002.53480.jhb@freebsd.org>
X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.2.7
 (bigwig.baldwin.cx); Fri, 20 Sep 2013 11:27:42 -0400 (EDT)
Cc: freebsd-current@freebsd.org
X-BeenThere: freebsd-current@freebsd.org
X-Mailman-Version: 2.1.14
Precedence: list
List-Id: Discussions about the use of FreeBSD-current
 <freebsd-current.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/options/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: Fri, 20 Sep 2013 15:27:43 -0000

On Friday, September 20, 2013 1:44:52 am Gleb Smirnoff wrote:
>   John,
> 
> On Thu, Sep 19, 2013 at 03:04:46PM -0400, John Baldwin wrote:
> J> >   When system is writing a kernel core dump, it issues watchdog
> J> > pat wdog_kern_pat(WD_LASTVAL). If ipmi is in action, it registers
> J> > ipmi_wd_event() as event for watchdog. Thus ipmi_wd_event() is
> J> > called in dumping context.
> J> > 
> J> > The problem is that ipmi_wd_event() calls into ipmi_set_watchdog(),
> J> > that calls into ipmi_alloc_request(), which uses M_WAITOK and
> J> > thus sleeps. This is a smaller problem, since can be converted to
> J> > M_NOWAIT. But ipmi_set_watchdog() then calls into
> J> > ipmi_submit_driver_request(), which calls msleep() any time.
> J> > 
> J> >   The attached patch allows me to successfully write cores in
> J> > presence of IPMI.
> J> 
> J> Of course, the watchdog might go off during your dump. :)
> 
> Yes, I understand that :(
> 
> But, imho patch improves situation, although is ugly.

Yes, I think a temporary workaround is fine for now.

> J> The real fix is more complicated, which is that we should not use
> J> a worker thread for at least SMIC and KCS.
> 
> -- 
> Totus tuus, Glebius.
> 

-- 
John Baldwin