linux-kernel - RE: [PATCH 3/6] x86/smpboot.c: Wake up offline CPU via mwait or nmi

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Date:	Mon, 4 Jun 2012 19:35:22 +0000
From:	"Yu, Fenghua" <fenghua.yu@...el.com>
To:	"Siddha, Suresh B" <suresh.b.siddha@...el.com>
CC:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	H Peter Anvin <hpa@...or.com>,
	"Luck, Tony" <tony.luck@...el.com>,
	"Mallick, Asit K" <asit.k.mallick@...el.com>,
	Arjan Dan De Ven <arjan@...ux.intel.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	x86 <x86@...nel.org>, linux-pm <linux-pm@...r.kernel.org>
Subject: RE: [PATCH 3/6] x86/smpboot.c: Wake up offline CPU via mwait or nmi

> From: Siddha, Suresh B
> Sent: Monday, June 04, 2012 11:59 AM
> To: Yu, Fenghua
> Cc: Ingo Molnar; Thomas Gleixner; H Peter Anvin; Luck, Tony; Mallick,
> Asit K; Arjan Dan De Ven; linux-kernel; x86; linux-pm
> Subject: Re: [PATCH 3/6] x86/smpboot.c: Wake up offline CPU via mwait
> or nmi
> 
> On Mon, 2012-06-04 at 11:17 -0700, Fenghua Yu wrote:
> > From: Fenghua Yu <fenghua.yu@...el.com>
> >
> > wakeup_secondary_cpu_via_soft() is defined to wake up offline CPU via
> mwait if
> > the CPU is in mwait or via nmi if the CPU is in hlt.
> >
> > A CPU boots up by INIT, INIT, STARTUP sequence when it boots up for
> the first
> > time during boot time or hot plug.
> 
> I think this breaks suspend/resume as the cpu state gets lost.
> 
> Have you tried suspend/resume?

Good catch! Suspend/resume is broken.

A pm callback can be installed to clear cpu_dead state in suspend preparation. So when resume, INIT sequence is used to wakeup CPU's just like the boot time case.

I have a quick fix and will put it in the next version of the patchset.

Thanks.

-Fenghua