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    SubjectRe: [linux-pm] pm-hibernate : possible circular locking dependency detected
    On Mon, 6 Apr 2009, Gautham R Shenoy wrote:

    > > If I understand correctly it isn't really a deadlock scenario, but it
    > > is a lockdep violation. The violation is:
    > >
    > > The pci_device_probe() path 2) proves that dpm_list_mtx [4] can
    > > be acquired while cpu_hotplug.lock [3] is held;
    > >
    > > The hibernate() path 3) proves that cpu_hotplug.lock [3] can be
    > > acquired while dpm_list_mtx [4] is held.
    > >
    > > The two pathways cannot run simultaneously (and hence cannot deadlock)
    > > because the prepare() stage of hibernation is supposed to stop all
    > > device probing. But lockdep will still report a problem.
    >
    > Thanks for clarifying this Alan. I guess it boils down to teaching
    > lockdep about this false-positive.

    Or else changing the code somehow to avoid the violation completely.
    But I have no idea how... And AFAIK, teaching lockdep about special
    cases like this is not so easy to do.

    Alan Stern



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