linux-kernel - Re: [PATCH 1/2] x86, reboot: revert stop_other

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Message-ID: <20120302211156.GM3083@redhat.com>
Date:	Fri, 2 Mar 2012 16:11:56 -0500
From:	Don Zickus <dzickus@...hat.com>
To:	Seiji Aguchi <seiji.aguchi@....com>
Cc:	"x86@...nel.org" <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	"tony.luck@...el.com" <tony.luck@...el.com>,
	"ak@...ux.intel.com" <ak@...ux.intel.com>,
	"mjg@...hat.com" <mjg@...hat.com>,
	"levinsasha928@...il.com" <levinsasha928@...il.com>
Subject: Re: [PATCH 1/2] x86, reboot: revert stop_other_cpus to using IRQ
 with NMI fallback

On Fri, Mar 02, 2012 at 03:41:57PM -0500, Seiji Aguchi wrote:
> 
> > +	/* if the REBOOT_VECTOR didn't work, try with the NMI */
> > +	if ((num_online_cpus() > 1) && (!smp_no_nmi_ipi))  {
> > +		if (register_nmi_handler(NMI_LOCAL, smp_stop_nmi_callback,
> > +					 NMI_FLAG_FIRST, "smp_stop"))
> 
> register_nmi_handler() doesn't work if kernel panics in nmi context because kzalloc() is called in register_nmi_handler() and 
> it may sleep.
> 
> register_nmi_handler() should be replaced with notifier_chain like kdump does.

I don't think kdump uses the notifier_chain.

Cheers,
Don
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