linux-kernel - Re: Reworking suspend-resume sequence (was: Re: PCI PM: Restore standard config registers of all devices early)

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Message-ID: <alpine.LFD.2.00.0902031114321.3247@localhost.localdomain>
Date:	Tue, 3 Feb 2009 11:19:48 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Jesse Barnes <jesse.barnes@...el.com>
cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andreas Schwab <schwab@...e.de>, Len Brown <lenb@...nel.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: Reworking suspend-resume sequence (was: Re: PCI PM: Restore
 standard config registers of all devices early)

On Tue, 3 Feb 2009, Linus Torvalds wrote:
> 
> Hmm. The _normal_ simple irq handler does this the way I described, but 
> for some reason the "handle_edge_irq()" does not. And the reason is 
> actually a buglet: it needs to mask things for the "recursive interrupt" 
> case.

Btw, just to clarify: none of this happens at the actual "irq_disable()" 
time: it only happens if you get an interrupt _while_ it's disabled. Which 
obviously shouldn't happen in the shutdown/wakeup path anyway for MSI, 
since the interrupts aren't shared, but it would be good to just be extra 
safe.

I do suspect we could/should just get rid of the msi masking entirely, but 
that may be too scary a step.

For the current suspend/resume situation, maybe it's enough to know that 
it shouldn't be happening anyway, and even if it _does_ happen on a device 
that has been shut down, it's just not going to do anything. Sure, it's 
doing that "writel/readl", but if it gets lost, who really cares? Nobody.

			Linus
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