* [PATCH] sched: fix BUG in preempt_notifier
@ 2015-07-01 6:33 Lidong Chen
2015-07-01 7:16 ` cfme_admin
2015-07-01 7:41 ` Wanpeng Li
0 siblings, 2 replies; 5+ messages in thread
From: Lidong Chen @ 2015-07-01 6:33 UTC (permalink / raw)
To: mingo, peterz; +Cc: linux-kernel, Lidong Chen
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(¬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)
{
--
2.1.0
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re:[PATCH] sched: fix BUG in preempt_notifier
2015-07-01 6:33 [PATCH] sched: fix BUG in preempt_notifier Lidong Chen
@ 2015-07-01 7:16 ` cfme_admin
2015-07-01 7:23 ` [PATCH] " Ingo Molnar
2015-07-01 7:41 ` Wanpeng Li
1 sibling, 1 reply; 5+ messages in thread
From: cfme_admin @ 2015-07-01 7:16 UTC (permalink / raw)
To: peterz, mingo, 我; +Cc: linux-kernel
[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain; charset=UTF-8, Size: 3076 bytes --]
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(¬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)
> {
>--
>2.1.0
>
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] sched: fix BUG in preempt_notifier
2015-07-01 7:16 ` cfme_admin
@ 2015-07-01 7:23 ` Ingo Molnar
0 siblings, 0 replies; 5+ messages in thread
From: Ingo Molnar @ 2015-07-01 7:23 UTC (permalink / raw)
To: cfme_admin; +Cc: peterz, mingo, linux-kernel
* cfme_admin <cfme_admin@163.com> wrote:
> 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.
This bug should already be fixed by this pending commit:
6efde1d3716b ("sched/preempt, kvm: Fix KVM preempt_notifier usage")
Attached below.
Thanks,
Ingo
========================>
>From 6efde1d3716b7d055d3310bccba2df244cf430d7 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@infradead.org>
Date: Thu, 25 Jun 2015 14:55:14 +0200
Subject: [PATCH] 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.fuchs@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Gleb Natapov <gleb@kernel.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Pontus Fuchs <pontus.fuchs@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 1cde2930e154 ("sched/preempt: Add static_key() to preempt_notifiers")
Link: http://lkml.kernel.org/r/20150625125514.GA3644@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@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 c86935a7f1f8..5bcf926e62a4 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 90977418aeb6..d7aafa0458a0 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);
}
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] sched: fix BUG in preempt_notifier
2015-07-01 6:33 [PATCH] sched: fix BUG in preempt_notifier Lidong Chen
2015-07-01 7:16 ` cfme_admin
@ 2015-07-01 7:41 ` Wanpeng Li
2015-07-02 0:38 ` cfme_admin
1 sibling, 1 reply; 5+ messages in thread
From: Wanpeng Li @ 2015-07-01 7:41 UTC (permalink / raw)
To: Lidong Chen, mingo, peterz; +Cc: linux-kernel
On 7/1/15 2:33 PM, Lidong Chen wrote:
> Signed-off-by: Lidong Chen <cfme_admin@163.com>
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<gleb@kernel.org>
Fixes: 1cde2930e154 ("sched/preempt: Add static_key() to preempt_notifiers")
Reported-and-Tested-by: Pontus Fuchs<pontus.fuchs@gmail.com>
Signed-off-by: Peter Zijlstra (Intel)<peterz@infradead.org>
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)
> {
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re:Re: [PATCH] sched: fix BUG in preempt_notifier
2015-07-01 7:41 ` Wanpeng Li
@ 2015-07-02 0:38 ` cfme_admin
0 siblings, 0 replies; 5+ messages in thread
From: cfme_admin @ 2015-07-02 0:38 UTC (permalink / raw)
To: Wanpeng Li; +Cc: mingo, peterz, linux-kernel
[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain; charset=UTF-8, Size: 3975 bytes --]
This is a better way to solve this bug.
Thanks.
At 2015-07-01 15:41:28, "Wanpeng Li" <wanpeng.li@hotmail.com> wrote:
>
>
>On 7/1/15 2:33 PM, Lidong Chen wrote:
>> Signed-off-by: Lidong Chen <cfme_admin@163.com>
>
>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<gleb@kernel.org>
>Fixes: 1cde2930e154 ("sched/preempt: Add static_key() to preempt_notifiers")
>Reported-and-Tested-by: Pontus Fuchs<pontus.fuchs@gmail.com>
>Signed-off-by: Peter Zijlstra (Intel)<peterz@infradead.org>
>
>
>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)
>> {
>
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^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2015-07-02 0:55 UTC | newest]
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2015-07-01 6:33 [PATCH] sched: fix BUG in preempt_notifier Lidong Chen
2015-07-01 7:16 ` cfme_admin
2015-07-01 7:23 ` [PATCH] " Ingo Molnar
2015-07-01 7:41 ` Wanpeng Li
2015-07-02 0:38 ` cfme_admin
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