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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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