On Wed, Nov 08, 2017 at 04:06:24PM +0000, James Morse wrote: > dpm_suspend() calls the freeze/thaw callbacks for hibernate before > disable_non_bootcpus() takes down secondaries. > > This leads to a fun race where the freeze/thaw callbacks reset the > SDEI interface (as we may be restoring a kernel with a different > layout due to KASLR), then the cpu-hotplug callbacks come in to > save the current state, which has already been reset. > > I tried to solve this with a 'frozen' flag that stops the hotplug > callback from overwriting the saved values. Instead this just > moves the race around and makes it even harder to think about. > > Instead, make it look like the secondaries have gone offline. > Call cpuhp_remove_state() in the freeze callback, this will call the > teardown hook on all online CPUs, then remove the state. This saves > all private events and makes future CPU up/down events invisible. > > Change sdei_event_unregister_all()/sdei_reregister_events() to > only save/restore shared events, which are all that is left. With > this we can remove the frozen flag. We can remove the device > suspend/resume calls too as cpuhotplug's teardown call has masked > the CPUs. > > All that is left is the reboot notifier, (which was abusing the > frozen flag). Call cpuhp_remove_state() to make it look like > secondary CPUs have gone offline. > > Suggested-by: Will Deacon <will.deacon@xxxxxxx> > Signed-off-by: James Morse <james.morse@xxxxxxx> > --- > drivers/firmware/arm_sdei.c | 60 +++++++++++++++++++++++---------------------- > 1 file changed, 31 insertions(+), 29 deletions(-) Thanks, this appears to address my concerns. It's too late for 4.15 now, but please resend for 4.16 and Catalin can pick this series up. Will -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
