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    SubjectRe: [PATCH] pciehp: Handle interrupts that happen during initialization.
    Eric W. Biederman wrote:
    > ebiederm@xmission.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.

    Thanks,
    Kenji Kaneshige




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