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

[poza@codeaurora.org]

On 2018-01-30 23:47, Keith Busch wrote:
> On Mon, Jan 29, 2018 at 10:34:44PM -0800, 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.
> 
> Okay, thanks for that information. I haven't got a DPC capable device 
> that
> supports INTx, so that's a gap in my current testing capabilities.
> 
> It looks like as you're suggesting, we should clear DPC Interrupt 
> Status
> in the top-half IRQ handler, and we should not see another DPC 
> interrupt
> raised until after we clear DPC Trigger Status in the bottom-half.

yes that's right. I am preparing a patch with that, and testing it on 
our platform.
please let me know on what branch should I post it ?
because other mail from Bjorn suggests me to post on pci/master. since 
he will take care of merging it.

Regards,
Oza.