At Fri, 3 Jul 2015 17:46:06 +0200, Paolo Bonzini wrote: > > > > On 03/07/2015 17:42, Peter Zijlstra wrote: > > On Fri, Jul 03, 2015 at 05:38:42PM +0200, Paolo Bonzini wrote: > >> So basically this. Can you reply with SoB and maybe Acked-by? > > > > Ah, thanks for doing that! > > > >> ------------- 8< --------------- > >> From: Peter Zijlstra <[email protected]> > >> Subject: [PATCH] sched, preempt_notifier: separate notifier registration > >> from static_key inc/dec > >> > >> Commit 1cde2930e154 ("sched/preempt: Add static_key() to > >> preempt_notifiers") > >> had two problems. First, the preempt-notifier API needs to sleep with the > >> addition of the static_key, we do however need to hold off preemption > >> while modifying the preempt notifier list, otherwise a preemption could > >> observe an inconsistent list state. KVM correctly registers and > >> unregisters preempt notifiers with preemption disabled, so the sleep > >> caused dmesg splats. > >> > >> Second, KVM registers and unregisters preemption notifiers very often > >> (in vcpu_load/vcpu_put). With a single uniprocessor guest the static key > >> would move between 0 and 1 continuously, hitting the slow path on every > >> userspace exit. > >> > >> To fix this, wrap the static_key inc/dec in a new API, and call it from > >> KVM. > >> > >> Fixes: 1cde2930e154 ("sched/preempt: Add static_key() to > >> preempt_notifiers") > >> Reported-by: Pontus Fuchs <[email protected]> > >> Reported-by: Takashi Iwai <[email protected]> > > > > Signed-off-by: Peter Zijlstra (Intel) <[email protected]> > > Ok, I'm crossing fingers and including this in my pull request in order > to preserve bisectability. Thanks.
I checked the patch now and confirmed that it fixes the regressions (the warnings and the sluggish mouse pointer). Feel free to my tested-by tag, if any. Tested-by: Takashi Iwai <[email protected]> Thanks! Takashi -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
