linux-kernel - Re: [patch, -git] pcie hotplug bootup crash fix

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Date:	Tue, 27 May 2008 15:45:07 -0700
From:	Kristen Carlson Accardi <kristen.c.accardi@...el.com>
To:	Jesse Barnes <jbarnes@...tuousgeek.org>
Cc:	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	"Rafael J. Wysocki" <rjw@...k.pl>, drzeus-list@...eus.cx
Subject: Re: [patch, -git] pcie hotplug bootup crash fix

On Mon, 26 May 2008 09:20:15 -0700
Jesse Barnes <jbarnes@...tuousgeek.org> wrote:

> On Monday, May 26, 2008 3:26 am Kenji Kaneshige wrote:
> > Andrew Morton wrote:
> > > On Mon, 26 May 2008 10:47:09 +0200 Ingo Molnar <mingo@...e.hu> wrote:
> > >> * Kenji Kaneshige <kaneshige.kenji@...fujitsu.com> wrote:
> > >>> I updated Ingo's patch. If it's ok, I'll send it to Jess Barnes with
> > >>> some other patches for the other pciehp regression problems.
> > >>
> > >> looks good to me, thanks Kenji.
> > >
> > > It's a bit sad to add a large workaround like this.  I'm surprised
> > > that fixing it properly is considered unviable for 2.6.26.  Normally
> > > these fixes are pretty simple - just request the IRQ a bit later?
> >
> > Although I have not considered how to implement proper fix deeply,
> > I don't think it's so simple. For example, current pciehp is doing
> > like this:
> >
> > (1) some initialization
> > (2) request_irq()
> > (3) issue command
> > (4) initialize slot data structure
> >
> > Maybe we want to do (2) after (4) to fix the problem. But if we
> > simply move (2) after (4), we cannot detect the command completion
> > event at (3) and it will cause command timeout.
> >
> > It's just an example, and there might be other things like this.
> > This example might be fixed simply, but all my worry is that fixing
> > this quickly might cause another regressions. This is why I think
> > Ingo's approach is better in a short term.
> >
> > And another reason is I'm very nervous because I already caused
> > many problems in pciehp since 2.6.26-rcX... :(
> 
> But you also fixed the problems, which is even more important! :)  I'm ok with 
> the workaround for 2.6.26 as long as we can get a more proper fix into 
> 2.6.27.
> 
> Any thoughts, Kristen?
> 
> Thanks,
> Jesse
> 

I'm in favor of the workaround for now.
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