linux-kernel - Re: WARNING: at arch/x86/kernel/smp.c:119 native_smp_send

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Message-ID: <20120210203117.GI5650@redhat.com>
Date:	Fri, 10 Feb 2012 15:31:17 -0500
From:	Don Zickus <dzickus@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	Sasha Levin <levinsasha928@...il.com>,
	Josh Boyer <jwboyer@...il.com>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Avi Kivity <avi@...hat.com>, kvm <kvm@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	x86 <x86@...nel.org>,
	Suresh B Siddha <suresh.b.siddha@...el.com>,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: Re: WARNING: at arch/x86/kernel/smp.c:119
 native_smp_send_reschedule+0x25/0x43()

On Fri, Feb 10, 2012 at 09:18:41PM +0100, Peter Zijlstra wrote:
> On Fri, 2012-02-10 at 15:02 -0500, Don Zickus wrote:
> > I also ran into the same problem you did and hacked up another patch that
> > checked a global atomic variable that let the system know we were shutting
> > down and not to do the WARN_ON (the global is already created for the NMI
> > case now). 
> 
> system_state seems like that thing.. 

except it doesn't seem to have a PANIC state, though we could add one I
suppose.

The thing is even if you reverted my changes:

e58d429 x86, reboot: Fix typo in nmi reboot path
bda6263 x86, NMI: Add knob to disable using NMI IPIs to stop cpus
3603a25 x86, reboot: Use NMI instead of REBOOT_VECTOR to stop cpus

I think you still run into the same problem because the reschedule code
changed.

So my second patch which I will eventually post will just skip the WARN_ON
if the system is going down.  Not sure if that is the proper way to address
this problem or change all of the stop_this_cpu code to use a different
bitmask than the cpu_online bitmask (but then you run the risk of a stuck
IPI I guess if the cpu is halted without notifying anyone).

Cheers,
Don
 
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