2015-07-01 06:34:16

by cfme_admin

Subject: [PATCH] sched: fix BUG in preempt_notifier

Signed-off-by: Lidong Chen <[email protected]>
---
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

2015-07-01 07:16:46

by cfme_admin

Subject: Re:[PATCH] sched: fix BUG in preempt_notifier

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" <[email protected]> wrote:
>Signed-off-by: Lidong Chen <[email protected]>
>---
> 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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2015-07-01 07:23:59

by Ingo Molnar

Subject: Re: [PATCH] sched: fix BUG in preempt_notifier

* cfme_admin <[email protected]> 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 <[email protected]>
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 <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Gleb Natapov <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Pontus Fuchs <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Fixes: 1cde2930e154 ("sched/preempt: Add static_key() to preempt_notifiers")
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
---
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(&notifier->link, &current->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(&notifier->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);
}

2015-07-01 07:41:43

by Wanpeng Li

Subject: Re: [PATCH] sched: fix BUG in preempt_notifier

On 7/1/15 2:33 PM, Lidong Chen wrote:
> Signed-off-by: Lidong Chen <[email protected]>

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<[email protected]>
Fixes: 1cde2930e154 ("sched/preempt: Add static_key() to preempt_notifiers")
Reported-and-Tested-by: Pontus Fuchs<[email protected]>
Signed-off-by: Peter Zijlstra (Intel)<[email protected]>


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(&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)
> {

2015-07-02 00:55:23

by cfme_admin

Subject: Re:Re: [PATCH] sched: fix BUG in preempt_notifier

This is a better way to solve this bug.
Thanks.

At 2015-07-01 15:41:28, "Wanpeng Li" <[email protected]> wrote:
>
>
>On 7/1/15 2:33 PM, Lidong Chen wrote:
>> Signed-off-by: Lidong Chen <[email protected]>
>
>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<[email protected]>
>Fixes: 1cde2930e154 ("sched/preempt: Add static_key() to preempt_notifiers")
>Reported-and-Tested-by: Pontus Fuchs<[email protected]>
>Signed-off-by: Peter Zijlstra (Intel)<[email protected]>
>
>
>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(&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)
>> {
>
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