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    SubjectRe: [PATCH 8/9] PCI / ACPI / PM: Platform support for PCI PME wake-up (rev. 7)
    On Sat, Feb 13, 2010 at 01:20:29AM +0100, Rafael J. Wysocki wrote:
    > On Friday 12 February 2010, Rafael J. Wysocki wrote:
    > > On Friday 12 February 2010, Gary Hade wrote:
    > ...
    > > > There seems to be a problem.
    > > >
    > > > The first time I booted I was able to successfully hot-remove
    > > > a PCIe card and then successfully hot-add it to a different slot.
    > > > When I tried to hot-remove a PCI-X card that was also present
    > > > during boot I saw that lingering blinking amber LED issue.
    > > >
    > > > After rebooting I tried the same thing but this time I did
    > > > not see the lingering blinking amber LED after removing the
    > > > PCI-X card but I did see it when removing the PCIe card.
    > > > I then tried to hot-add the PCIe card to a different slot
    > > > and noticed the below messages.
    > > >
    > > > I don't think I will be able to try to characterize this
    > > > better or test any more patches until Monday.
    > >
    > > OK, thanks for testing.
    > >
    > > It seems we have a deadlock on pci_acpi_notify_mtx, but I'm yet to understand
    > > the exact mechanism of it.
    >
    > In fact there are two problems in there. First, the bridge event notification
    > calls handle_bridge_insertion() which attempts to install a PM notifier for
    > the bridge and that deadlocks, because it tries to acquire the mutex
    > recursively. Second, apparently, init_bridge_misc() may be called in the
    > notification code path and it attempts to unregister the notifier and register
    > it again, which can't be done with pci_acpi_notify_mtx held.
    >
    > I guess there are similar problems on the hot remove notification path.
    >
    > Anyway, I have a new version of the patch and I'm going to test it a bit
    > over the weekend. Unfortunately, I don't have hardware with PCI hotplug
    > capability, so I'll send you the new patch for testing on Monday, if you don't
    > mind.

    I don't mind. Although I am concerned that my acpiphp only
    testing on our IBM System x boxes may not be sufficient to
    assure that PCI hotplug will work well on other PCI hotplug
    capable systems. I hope that others will also do some early
    testing of this code.

    Gary

    --
    Gary Hade
    System x Enablement
    IBM Linux Technology Center
    503-578-4503 IBM T/L: 775-4503
    garyhade@us.ibm.com
    http://www.ibm.com/linux/ltc



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