On Fri, 05 Feb 2010 10:31:42 +0200 Maxim Levitsky <maximlevitsky@xxxxxxxxx> wrote: > On Thu, 2010-02-04 at 16:09 -0800, Andrew Morton wrote: > > On Fri, 5 Feb 2010 01:18:15 +0200 Maxim Levitsky <maximlevitsky@xxxxxxxxx> wrote: > > > > > Currently removal of the card leads to del_disk called indirectly by mmc core. > > > This function expects userspace to be running, which isn't when .resume is called > > > > > > Fix that by removing the code that did that in mmc_resume_host. It is possible > > > because card detection logic will kick it later and remove the card. > > > > I don't really understand. The above implies that to trigger this bug, > > one needs to physically remove the card during a resume operation. ie: > > a human-vs-computer race. Sounds unlikely? > > > > So... exactly what steps does the user need to take to trigger this > > Sorry for describing this poorly. > The steps are: > > -> Have a kernel with CONFIG_MMC_UNSAFE_RESUME > -> Insert MMC/SD card > -> Suspend/hibernate the system > -> While system is hibernated/suspended pull the card off > -> Resume the system > -> Hang > > > if CONFIG_MMC_UNSAFE_RESUME is set, mmc core allows the user to > suspend/resume the card normally assuming he won't change the card or > modify it in another system. The former case is actually handled quite > well. > > if CONFIG_MMC_UNSAFE_RESUME isn't set, it removes the card during > suspend, and I now think (and will test) that this will still hang the > system this time on suspend. > > Maybe we can make del_disk behave well if called with userspace frozen? > After all if user calls it, very likely that hardware is absent thus > there is no point in syncing (which I think triggers the hang).... > There is no del_disk in the kernel. Let's be more specific (and accurate!) about the hang. I assume it's mmc_remove_card->device_del->kobject_uevent? Yes, I'd have thought that it would be a good idea for the kobject_uevent code (or lower, in call_usermodehelper) to take avoiding action if userspace is frozen. However such action would probably involve doing a WARN_ON() too, so we'd still need MMC changes to avoid that. _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
