Re: [RFC PATCH] genirq: introduce handle_fasteoi_edge_irq flow handler

[Yipeng Zou]

在 2023/4/14 19:25, Marc Zyngier 写道:
> On Fri, 10 Mar 2023 10:14:17 +0000,
> Yipeng Zou <zouyipeng@xxxxxxxxxx> wrote:
> > Recently, We have a LPI migration issue on the ARM SMP platform.
> >
> > For example, NIC device generates MSI and sends LPI to CPU0 via ITS,
> > meanwhile irqbalance running on CPU1 set irq affinity of NIC to CPU1,
> > the next interrupt will be sent to CPU2, due to the state of irq is
> > still in progress, kernel does not end up performing irq handler on
> > CPU2, which results in some userland service timeouts, the sequence
> > of events is shown as follows:
> >
> > NIC                     CPU0                    CPU1
> >
> > Generate IRQ#1          READ_IAR
> >                          Lock irq_desc
> >                          Set IRQD_IN_PROGRESS
> >                          Unlock irq_desc
> >                                                  Lock irq_desc
> >                                                  Change LPI Affinity
> >                                                  Unlock irq_desc
> >                          Call irq_handler
> > Generate IRQ#2
> >                                                  READ_IAR
> >                                                  Lock irq_desc
> >                                                  Check IRQD_IN_PROGRESS
> >                                                  Unlock irq_desc
> >                                                  Return from interrupt#2
> >                          Lock irq_desc
> >                          Clear IRQD_IN_PROGRESS
> >                          Unlock irq_desc
> >                          return from interrupt#1
> >
> > For this scenario, The IRQ#2 will be lost. This does cause some exceptions.
> Please see my reply to James at [1]. I'd appreciate if you could give
> that patch a go, which I expect to be a better avenue to fix what is
> effectively a GIC architecture defect.
>
> Thanks,
>
> 	M.
>
> [1] https://lore.kernel.org/all/86pm89kyyt.wl-maz@xxxxxxxxxx/

Hi Marc:

    Thanks for your time about this issue.

    I have seen your latest patch, and I am preparing the environment 
for testing, I will sent the testing status of this patch later.

--
Regards,
Yipeng Zou