Re: [PATCH 2/6] PCI/DPC: Leave interrupts enabled while handling event

[poza@codeaurora.org]

On 2018-01-30 12:04, poza@codeaurora.org wrote:
> On 2018-01-30 11:59, Oza Pawandeep wrote:
>> + Oza
>> 
>> On Tue, Jan 30, 2018 at 7:41 AM, Sinan Kaya <okaya@codeaurora.org> 
>> wrote:
>>> On 1/29/2018 4:31 PM, Keith Busch wrote:
>>>> +     if (!work_busy(&dpc->work))
>>>> +             schedule_work(&dpc->work);
>>> 
>>> Isn't there a race condition between the time that dpc_work() clears 
>>> PCI_EXP_DPC_STATUS
>>> register and when work actually completes by returning from 
>>> dpc_work()?
>>> 
>>> If the interrupt arrives just in this window, this code will not 
>>> schedule the work.
>>> 
>>> --
>>> Sinan Kaya
>>> Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm 
>>> Technologies, Inc.
>>> Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a 
>>> Linux Foundation Collaborative Project.
> 
> besides, there is one more problem which I was debugging:
> if RP doesnt support MSI, then legacy interrupts are not well handled
> and we get interrupt storm.
> this is because;
> PCI_EXP_DPC_STATUS_INTERRUPT is being cleared in deferred work.
> which should get cleared in dpc_irq interrupt handler.
> I will post a patch for this, but I see there are lot of changes being
> made in dpc and aer lately.
> 
> Bjorn: Can you please help to review my AER/DPC series of patches so
> that I do not have to keep rebasing and do manual merge ?
> 
> Regards,
> Oza.

the DPC code assumes that the interrupt will be edge triggered (MSI), 
and clears interrupt in deferred work.
but for SPI (level triggered) it should be cleared in dpc_irq.

Regards,
Oza.