linux-kernel - Re: [PATCH V5 3/3] PCI: Mask and unmask hotplug interrupts during reset

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Date:   Tue, 03 Jul 2018 19:40:46 +0530
From:   poza@...eaurora.org
To:     Lukas Wunner <lukas@...ner.de>
Cc:     Sinan Kaya <okaya@...eaurora.org>, linux-pci@...r.kernel.org,
        linux-arm-msm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Keith Busch <keith.busch@...el.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V5 3/3] PCI: Mask and unmask hotplug interrupts during
 reset

On 2018-07-03 19:29, Lukas Wunner wrote:
> On Tue, Jul 03, 2018 at 09:31:24AM -0400, Sinan Kaya wrote:
>> Issue is observing hotplug link down event in the middle of AER 
>> recovery
>> as in my previous reply.
>> 
>> If we mask hotplug interrupts before secondary bus reset via my patch,
>> then hotplug driver will not observe both link up and link down 
>> interrupts.
>> 
>> If we don't mask hotplug interrupts, we have a race condition.
> 
> I assume that a bus reset not only causes a link and presence event but
> also clears the Presence Detect State bit in the Slot Status register
> and the Data Link Layer Link Active bit in the Link Status register
> momentarily.
> 
> pciehp may access those two bits concurrently to the AER driver
> performing a slot reset.  So it may not be sufficient to mask
> the interrupt.

Was just wondering that you are protecting Presence Detect State bit 
with reset_lock, mainly in pciehp_ist
but with hotplug interrupt disabled, is there another way that it 
hotplug code gets activated ?

> 
> I've posted this patch to address the issue:
> https://patchwork.ozlabs.org/patch/930391/
> 
> Thanks,
> 
> Lukas