From mboxrd@z Thu Jan  1 00:00:00 1970
From: Don Zickus <dzickus@redhat.com>
Subject: Re: WARNING: at arch/x86/kernel/smp.c:119
 native_smp_send_reschedule+0x25/0x43()
Date: Fri, 23 Mar 2012 09:26:48 -0400
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Cc: Peter Zijlstra <peterz@infradead.org>,
	"Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>,
	Josh Boyer <jwboyer@gmail.com>,
	"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@elte.hu>,
	Thomas Gleixner <tglx@linutronix.de>,
	Avi Kivity <avi@redhat.com>, kvm <kvm@vger.kernel.org>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	x86 <x86@kernel.org>,
	Suresh B Siddha <suresh.b.siddha@intel.com>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
To: Sasha Levin <levinsasha928@gmail.com>
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On Fri, Mar 23, 2012 at 12:47:38PM +0200, Sasha Levin wrote:
> I'm just wondering about the status of the patches to fix this issue,
> this is still happening on linux-next.

I got distracted with other stuff.  I have been running code that does =
the
following in the shutdown path:

foreach_online_cpu
    cpu_down

but I get occasional hangs on reboot that I haven't gotten around to
debugging.  I assumed this is the approach Peter was suggesting though =
I
don't think he was sure if it was going to be reliable.

Cheers,
Don

>=20
> On Fri, Feb 10, 2012 at 11:04 PM, Don Zickus <dzickus@redhat.com> wro=
te:
> > On Fri, Feb 10, 2012 at 09:36:03PM +0100, Peter Zijlstra wrote:
> >> On Fri, 2012-02-10 at 15:31 -0500, Don Zickus wrote:
> >> > So my second patch which I will eventually post will just skip t=
he WARN_ON
> >> > if the system is going down. =A0Not sure if that is the proper w=
ay to address
> >> > this problem or change all of the stop_this_cpu code to use a di=
fferent
> >> > bitmask than the cpu_online bitmask (but then you run the risk o=
f a stuck
> >> > IPI I guess if the cpu is halted without notifying anyone).
> >>
> >> Yeah, the async hard kill of all cpus is bound to make problems.. =
what
> >> I'm wondering is, why is this in the normal shutdown path and not
> >> specific to a hard panic?
> >
> > I didn't write the original code, I just changed it from REBOOT_IRQ=
 to
> > NMI and left all the stop_this_cpu stuff alone.
> >
> >>
> >> Trying to make this work is just not going to be pretty, and in th=
e
> >> panic case we really don't care much.
> >
> > Sure.
> >
> > Cheers,
> > Don