On Mon, 2009-04-06 at 21:58 +0200, Rafael J. Wysocki wrote: > On Monday 06 April 2009, Alan Stern wrote: > > 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. > > Yeah, I've just wanted to ask about that. Peter, how can we do it? I think it would come down to modeling that blocking of probes as a lock or something -- because that's basically what it is. So on the regular probe path, take a read lock of this lock, and on the suspend path take it as write or something. _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
