Date: Thu, 16 Feb 2012 16:56:03 -0500
From: Don Zickus <dzickus@redhat.com>
To: Yinghai Lu <yinghai@kernel.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>, linux-kernel@vger.kernel.org,
        mingo@redhat.com, hpa@zytor.com, torvalds@linux-foundation.org,
        kexec@lists.infradead.org, vgoyal@redhat.com,
        akpm@linux-foundation.org, tglx@linutronix.de, mingo@elte.hu,
        linux-tip-commits@vger.kernel.org
Subject: Re: [tip:x86/debug] x86/kdump: No need to disable ioapic/ lapic in
 crash path
Message-ID: <20120216215603.GH9751@redhat.com>
References: <tip-d9bc9be89629445758670220787683e37c93f6c1@git.kernel.org>
 <CAE9FiQWRjvu_uNcx_bJXYHeg4D4k6YzHHmSudsq7EyubLi7+nw@mail.gmail.com>
 <m1ipjc3fsk.fsf@fess.ebiederm.org>
 <CAE9FiQVLnyRB+pAqi22C5mCbHOOVKxsBhQKaB6P0p9f2LBL8bA@mail.gmail.com>
 <m1zkcmyjyd.fsf@fess.ebiederm.org>
 <CAE9FiQVj12UCGbOe4wZfx-L8tdab-1si-RA=vBnNeZ7cUNqyyg@mail.gmail.com>
 <CAE9FiQVPnO8-tuPoio0Wxv=8rjdm2tJbBk3+3ystueyYtZn9BA@mail.gmail.com>
 <20120216172735.GX9751@redhat.com>
 <CAE9FiQVhbAM9vjx-uFcuc0ndsUp0aez9_TsQHStje5G5iwYbag@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <CAE9FiQVhbAM9vjx-uFcuc0ndsUp0aez9_TsQHStje5G5iwYbag@mail.gmail.com>
User-Agent: Mutt/1.5.21 (2010-09-15)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1124
Lines: 34

On Thu, Feb 16, 2012 at 01:53:29PM -0800, Yinghai Lu wrote:
> On Thu, Feb 16, 2012 at 9:27 AM, Don Zickus <dzickus@redhat.com> wrote:
> 
> > So I think I figured it out. ?I went through and commented out code in
> > disable_local_APIC until I narrowed it down to the piece of code that
> > needs to be disabled for it to work.
> >
> > Surprise, surprise... its LVTPC or perf! :-) ?Actually it is the
> > nmi_watchdog which uses perf. ?My theory is NMIs are not disabled and one
> > is generated by the local apic during decompression (just bad timing) and
> > *splat*.
> >
> > Yinghai, you can probably prove this by
> >
> > echo 0 > /proc/sys/kernel/nmi_watchdog
> >
> > then do your kdump crash test.
> 
> yes.  that will make kdump crash working.

Cool.  Thanks.

Eric,

Just let me know how you want to handle disabling NMIs in the kexec in
panic shutdown case.

Cheers,
Don
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/