Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752812AbbGAHln (ORCPT ); Wed, 1 Jul 2015 03:41:43 -0400 Received: from blu004-omc1s37.hotmail.com ([65.55.116.48]:52873 "EHLO BLU004-OMC1S37.hotmail.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751075AbbGAHlf (ORCPT ); Wed, 1 Jul 2015 03:41:35 -0400 X-TMN: [ElYLJX5rcDXChCAKrvsTQQwxZMjVh+qC] X-Originating-Email: [wanpeng.li@hotmail.com] Message-ID: Subject: Re: [PATCH] sched: fix BUG in preempt_notifier To: Lidong Chen , mingo@redhat.com, peterz@infradead.org References: <1435732410-18060-1-git-send-email-cfme_admin@163.com> CC: linux-kernel@vger.kernel.org From: Wanpeng Li Date: Wed, 1 Jul 2015 15:41:28 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:38.0) Gecko/20100101 Thunderbird/38.0.1 MIME-Version: 1.0 In-Reply-To: <1435732410-18060-1-git-send-email-cfme_admin@163.com> Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 01 Jul 2015 07:41:33.0871 (UTC) FILETIME=[5A539BF0:01D0B3D1] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3834 Lines: 112 On 7/1/15 2:33 PM, Lidong Chen wrote: > Signed-off-by: Lidong Chen Subject: sched,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. Cc: Gleb Natapov Fixes: 1cde2930e154 ("sched/preempt: Add static_key() to preempt_notifiers") Reported-and-Tested-by: Pontus Fuchs Signed-off-by: Peter Zijlstra (Intel) If this commit in tip tree fix your bug? Regards, Wanpeng Li > --- > kernel/sched/core.c | 25 ++++--------------------- > 1 file changed, 4 insertions(+), 21 deletions(-) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index b803e1b..4a5a964 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -2318,15 +2318,12 @@ void wake_up_new_task(struct task_struct *p) > > #ifdef CONFIG_PREEMPT_NOTIFIERS > > -static struct static_key preempt_notifier_key = STATIC_KEY_INIT_FALSE; > - > /** > * preempt_notifier_register - tell me when current is being preempted & rescheduled > * @notifier: notifier struct to register > */ > void preempt_notifier_register(struct preempt_notifier *notifier) > { > - static_key_slow_inc(&preempt_notifier_key); > hlist_add_head(¬ifier->link, ¤t->preempt_notifiers); > } > EXPORT_SYMBOL_GPL(preempt_notifier_register); > @@ -2340,11 +2337,10 @@ EXPORT_SYMBOL_GPL(preempt_notifier_register); > void preempt_notifier_unregister(struct preempt_notifier *notifier) > { > hlist_del(¬ifier->link); > - static_key_slow_dec(&preempt_notifier_key); > } > EXPORT_SYMBOL_GPL(preempt_notifier_unregister); > > -static void __fire_sched_in_preempt_notifiers(struct task_struct *curr) > +static void fire_sched_in_preempt_notifiers(struct task_struct *curr) > { > struct preempt_notifier *notifier; > > @@ -2352,14 +2348,9 @@ static void __fire_sched_in_preempt_notifiers(struct task_struct *curr) > notifier->ops->sched_in(notifier, raw_smp_processor_id()); > } > > -static __always_inline void fire_sched_in_preempt_notifiers(struct task_struct *curr) > -{ > - if (static_key_false(&preempt_notifier_key)) > - __fire_sched_in_preempt_notifiers(curr); > -} > > static void > -__fire_sched_out_preempt_notifiers(struct task_struct *curr, > +fire_sched_out_preempt_notifiers(struct task_struct *curr, > struct task_struct *next) > { > struct preempt_notifier *notifier; > @@ -2368,21 +2359,13 @@ __fire_sched_out_preempt_notifiers(struct task_struct *curr, > notifier->ops->sched_out(notifier, next); > } > > -static __always_inline void > -fire_sched_out_preempt_notifiers(struct task_struct *curr, > - struct task_struct *next) > -{ > - if (static_key_false(&preempt_notifier_key)) > - __fire_sched_out_preempt_notifiers(curr, next); > -} > - > #else /* !CONFIG_PREEMPT_NOTIFIERS */ > > -static inline void fire_sched_in_preempt_notifiers(struct task_struct *curr) > +static void fire_sched_in_preempt_notifiers(struct task_struct *curr) > { > } > > -static inline void > +static void > fire_sched_out_preempt_notifiers(struct task_struct *curr, > struct task_struct *next) > { -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/