linux-kernel - Re: [PATCH] pciehp: Handle interrupts that happen during initialization.

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Date:	Sat, 14 Feb 2009 06:56:41 -0800
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Jesse Barnes <jbarnes@...tuousgeek.org>
Cc:	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] pciehp:  Handle interrupts that happen during initialization.

ebiederm@...ssion.com (Eric W. Biederman) writes:

> And on the big gotcha's I have found one more I am tracking.
>
> I am seeing pci bridges with a NULL pointer for the subordinate bus.
> Earlier I had thought that this was a symptom of the double remove
> but I have been able to reproduce it without that.
>
> On just a little bit deeper investigation it looks like the cases
> are dying are all coming when the nested bridge reappears.
>
> Which is wrong on so many levels as I am toggle power to the outer
> slot, so the nested bridge should not even exist at that time.  Ugh.
> More tracing to for me on that one.

Ok. Got it.  I was processing the interrupt for a device after it had
been hot removed but before the device state had disappeared.

pcie_isr looks like it would be even worse in that situation.  Looping forever
if pciehp_readw(ctrl, PCIE_EXPSLTA) always succeed sand returns 0xffff.

That loop in there appears impossibly misguided.  If the pending interrupt
values change after you have received the interrupt another instance
of the same interrupt should be pending so the loop should be completely
unnecessary.

Eric

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