linux-kernel - Re: xen: IPI interrupts not resumed early enough on suspend/resume

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Date:	Mon, 3 Oct 2011 20:42:20 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Ian Campbell <Ian.Campbell@...rix.com>
cc:	Jeremy Fitzhardinge <Jeremy.Fitzhardinge@...rix.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	xen-devel <xen-devel@...ts.xensource.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: xen: IPI interrupts not resumed early enough on suspend/resume

On Mon, 3 Oct 2011, Ian Campbell wrote:
> I can see a few options for how I might go about solving this in a
> non-hacky way, which approach do you think would be preferable:

The question is whether you need to disable the IPI interrupt at
all. If not, we have a flag for that.
 
>       * Add "IRQF_RESUME_EARLY", driven from syscore_resume, and use it
>         for these interrupts.

That's the preferable solution, as we could use that for PPC as well,
unless we can move stuff around, so we disable stuff later. 

>       * register syscore ops for the Xen event channel subsystem to
>         unmask the IPIs earlier (would probably look a lot like the code
>         removed by 676dc3cf5bc3).

I'd like to avoid that.

>       * add syscore_ops to Xen smp subsystem to unmask the specific IPIs
>         (which it binds at start of day) earlier.
>       * push dpm_(suspend|resume)_noirq down into stop machine region

Where is stomp machine used?

>       * use something other than stop_machine to quiesce system and move
>         to cpu0 for suspend (doesn't seem sensible to reproduce that
>         functionality).

We already shut down the nonboot cpus on suspend. We could do that
_before_ we disable devices and the interrupts.
 
Raphael ?

Thanks,

	tglx
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