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

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Date:	Wed, 18 Feb 2009 14:48:49 +0900
From:	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	Jesse Barnes <jbarnes@...tuousgeek.org>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] pciehp:  Handle interrupts that happen during initialization.

Eric W. Biederman wrote:
> Kenji Kaneshige <kaneshige.kenji@...fujitsu.com> writes:
> 
>> Eric W. Biederman wrote:
>>> 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.
>>>
>> For level-triggered interrupt, I think it's true.
>>
>> But for edge-triggered interrupt, I don't think it's true. I think
>> only one interrupt is generated if the first hotplug event occurs
>> and the second hotplug event occurs before clearing the status of
>> first hotplug event.
> 
> My test case is edge-triggered MSI's.  The issue is that I get an interrupt
> from the card that I am unplugging, but by the time the interrupt handler
> is executed the card is physically absent, but the pci_dev structure is
> still present in the kernel.
> 

Ok, I understood what is happening. Could you try the following patch?
It is currently in Jesse's linux-next.

http://marc.info/?l=linux-pci&m=123364118418484&w=2

BTW, I don't think surprise removal is well tested.

Thanks,
Kenji Kaneshige


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