Date: Wed, 1 Jul 2015 15:16:06 +0800 (CST)
From: cfme_admin <cfme_admin@163.com>
To: "peterz@infradead.org" <peterz@infradead.org>,
        "mingo@redhat.com" <mingo@redhat.com>,
        =?UTF-8?B?5oiR?= <cfme_admin@163.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re:[PATCH] sched: fix BUG in preempt_notifier
In-Reply-To: <1435732410-18060-1-git-send-email-cfme_admin@163.com>
References: <1435732410-18060-1-git-send-email-cfme_admin@163.com>
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more information about the bug is below:
https://bugzilla.kernel.org/show_bug.cgi?id=100701

the preempt_notifier_unregister function is run in_atomic context, but static_key_slow_dec function may cause sleep.


At 2015-07-01 14:33:30, "Lidong Chen" <cfme_admin@163.com> wrote:
>Signed-off-by: Lidong Chen <cfme_admin@163.com>
>---
> 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(&notifier->link, &current->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(&notifier->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)
> {
>-- 
>2.1.0
>
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