On 7 Mar 2005, Eric W. Biederman wrote: > David Brownell <[EMAIL PROTECTED]> writes: > > > On Monday 07 March 2005 2:08 pm, Eric W. Biederman wrote: > > > > > > > > The ongoing DMA transfers which are companions of the irq generating > > > events are what really concern me, as we could get all kinds of > > > interesting memory stomps. Do you think you could implement > > > a reboot notifier or a shutdown() method to handle that case? > > > > > > This appears to be yet another case of kexec transforming theoretical > > > bugs into actual ones. Groan. > > > > Reboot notifiers seem to be a more general solution than the > > driver model shutdown() hooks, since as Alan noted not every > > bus framework uses shutdown() ... and although remove() would > > solve the issue too, for essentially all busses, it doesn't > > kick in here (and linker tricks may have removed it anyway). > > shutdown()/remove() are better in that they are more likely > to get any ordering requirements correct. Making the > connection between a reboot notifier and a driver is a messing > proposition. > > Possibly a version of suspend that only would quiesce the device > would work as well.
I can implement either a shutdown method or a reboot notifier for uhci-hcd. Note however that the upcoming changes to the PM core include a suspend call (PMSG_FREEZE) that does exactly what you want: quiesce the device, disable IRQ and DMA, but don't necessarily switch the power level. (See Documentation/power/devices.txt.) Unfortunately it won't be implemented until another few kernel releases have gone by. The idea of using kexec to recover from a partially-damaged kernel seems unreliable. Even attempting to quiesce devices prior to rebooting may not work because of locks whose owners have crashed. > There used to be documentation in Documentation/driver-model/ > for the shutdown() method but it is no longer there. > > It looks fairly clear that shutdown() has not been implemented > to any reasonable degree so it may be time to revisit that. > > The whole linux reboot path is a mess. Indeed. Alan Stern ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
