On 30/06/2015 13:10, tip-bot for Peter Zijlstra wrote: > Commit-ID: 6efde1d3716b7d055d3310bccba2df244cf430d7 > Gitweb: http://git.kernel.org/tip/6efde1d3716b7d055d3310bccba2df244cf430d7 > Author: Peter Zijlstra <pet...@infradead.org> > AuthorDate: Thu, 25 Jun 2015 14:55:14 +0200 > Committer: Ingo Molnar <mi...@kernel.org> > CommitDate: Tue, 30 Jun 2015 07:58:53 +0200 > > sched/preempt, kvm: Fix KVM preempt_notifier usage > > 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. > > There is no reason to have preemption disabled in the caller, > registering a preempt notifier is a purely task local affair. > > Therefore move the preempt_disable into the functions and change > the callers to a preemptible context. > > Reported-and-Tested-by: Pontus Fuchs <pontus.fu...@gmail.com> > Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org> > Cc: Andrew Morton <a...@linux-foundation.org> > Cc: Borislav Petkov <b...@alien8.de> > Cc: Gleb Natapov <g...@kernel.org> > Cc: H. Peter Anvin <h...@zytor.com> > Cc: Linus Torvalds <torva...@linux-foundation.org> > Cc: Peter Zijlstra <pet...@infradead.org> > Cc: Pontus Fuchs <pontus.fu...@gmail.com> > Cc: Thomas Gleixner <t...@linutronix.de> > Fixes: 1cde2930e154 ("sched/preempt: Add static_key() to preempt_notifiers") > Link: > http://lkml.kernel.org/r/20150625125514.ga3...@twins.programming.kicks-ass.net > Signed-off-by: Ingo Molnar <mi...@kernel.org> > --- > kernel/sched/core.c | 11 +++++++++++ > virt/kvm/kvm_main.c | 5 +++-- > 2 files changed, 14 insertions(+), 2 deletions(-) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index c86935a..5bcf926 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -2138,7 +2138,12 @@ static struct static_key preempt_notifier_key = > STATIC_KEY_INIT_FALSE; > void preempt_notifier_register(struct preempt_notifier *notifier) > { > static_key_slow_inc(&preempt_notifier_key); > + /* > + * Avoid preemption while changing the preempt notifier list. > + */ > + preempt_disable(); > hlist_add_head(¬ifier->link, ¤t->preempt_notifiers); > + preempt_enable(); > } > EXPORT_SYMBOL_GPL(preempt_notifier_register); > > @@ -2150,7 +2155,13 @@ EXPORT_SYMBOL_GPL(preempt_notifier_register); > */ > void preempt_notifier_unregister(struct preempt_notifier *notifier) > { > + /* > + * Avoid preemption while changing the preempt notifier list. > + */ > + preempt_disable(); > hlist_del(¬ifier->link); > + preempt_enable(); > + > static_key_slow_dec(&preempt_notifier_key); > } > EXPORT_SYMBOL_GPL(preempt_notifier_unregister); > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index 9097741..d7aafa0 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -128,8 +128,9 @@ int vcpu_load(struct kvm_vcpu *vcpu) > > if (mutex_lock_killable(&vcpu->mutex)) > return -EINTR; > - cpu = get_cpu(); > preempt_notifier_register(&vcpu->preempt_notifier); > + > + cpu = get_cpu(); > kvm_arch_vcpu_load(vcpu, cpu); > put_cpu(); > return 0; > @@ -139,8 +140,8 @@ void vcpu_put(struct kvm_vcpu *vcpu) > { > preempt_disable(); > kvm_arch_vcpu_put(vcpu); > - preempt_notifier_unregister(&vcpu->preempt_notifier); > preempt_enable(); > + preempt_notifier_unregister(&vcpu->preempt_notifier); > mutex_unlock(&vcpu->mutex); > } > >
NACK. Paolo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
