diff mbox series

sched/eevdf: Avoid NULL in pick_eevdf

Message ID 20231120073821.1304-1-xuewen.yan@unisoc.com
State New
Headers
Series sched/eevdf: Avoid NULL in pick_eevdf |

Commit Message

Xuewen Yan Nov. 20, 2023, 7:38 a.m. UTC 
  Now in pick_eevdf function, add the pick_first_entity to prevent
picking null when using eevdf, however, the leftmost may be null.
As a result, it would cause oops because the se is NULL.

Fix this by compare the curr and left, if the left is null, set
the se be curr.

Fixes: 147f3efaa241 ("sched/fair: Implement an EEVDF-like scheduling policy")
Signed-off-by: Xuewen Yan <xuewen.yan@unisoc.com>
---
 kernel/sched/fair.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

Comments

Abel Wu Nov. 20, 2023, 8:49 a.m. UTC | #1 
Hi Xuewen, the pick part has been re-worked, would you please re-test
with the newest branch?

Thanks,
	Abel

https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/?h=sched%2Fcore

On 11/20/23 3:38 PM, Xuewen Yan Wrote:
> Now in pick_eevdf function, add the pick_first_entity to prevent
> picking null when using eevdf, however, the leftmost may be null.
> As a result, it would cause oops because the se is NULL.
> 
> Fix this by compare the curr and left, if the left is null, set
> the se be curr.
> 
> Fixes: 147f3efaa241 ("sched/fair: Implement an EEVDF-like scheduling policy")
> Signed-off-by: Xuewen Yan <xuewen.yan@unisoc.com>
> ---
>   kernel/sched/fair.c | 18 +++++++++++++++++-
>   1 file changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index d7a3c63a2171..10916f6778ac 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -951,12 +951,28 @@ static struct sched_entity *__pick_eevdf(struct cfs_rq *cfs_rq)
>   	return NULL;
>   }
>   
> +/* Just simply choose the se with the smallest vruntime */
> +static struct sched_entity *__pick_cfs(struct cfs_rq *cfs_rq)
> +{
> +	struct sched_entity *curr = cfs_rq->curr;
> +	struct sched_entity *left = __pick_first_entity(cfs_rq);
> +
> +	/*
> +	 * If curr is set we have to see if its left of the leftmost entity
> +	 * still in the tree, provided there was anything in the tree at all.
> +	 */
> +	if (!left || (curr && entity_before(curr, left)))
> +		left = curr;
> +
> +	return left;
> +}
> +
>   static struct sched_entity *pick_eevdf(struct cfs_rq *cfs_rq)
>   {
>   	struct sched_entity *se = __pick_eevdf(cfs_rq);
>   
>   	if (!se) {
> -		struct sched_entity *left = __pick_first_entity(cfs_rq);
> +		struct sched_entity *left = __pick_cfs(cfs_rq);
>   		if (left) {
>   			pr_err("EEVDF scheduling fail, picking leftmost\n");
>   			return left;
Xuewen Yan Nov. 21, 2023, 5:08 a.m. UTC | #2 
On Mon, Nov 20, 2023 at 4:49 PM Abel Wu <wuyun.abel@bytedance.com> wrote:
>
> Hi Xuewen, the pick part has been re-worked, would you please re-test
> with the newest branch?

Okay, Thanks!

>
> Thanks,
>         Abel
>
> https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/?h=sched%2Fcore
>
> On 11/20/23 3:38 PM, Xuewen Yan Wrote:
> > Now in pick_eevdf function, add the pick_first_entity to prevent
> > picking null when using eevdf, however, the leftmost may be null.
> > As a result, it would cause oops because the se is NULL.
> >
> > Fix this by compare the curr and left, if the left is null, set
> > the se be curr.
> >
> > Fixes: 147f3efaa241 ("sched/fair: Implement an EEVDF-like scheduling policy")
> > Signed-off-by: Xuewen Yan <xuewen.yan@unisoc.com>
> > ---
> >   kernel/sched/fair.c | 18 +++++++++++++++++-
> >   1 file changed, 17 insertions(+), 1 deletion(-)
> >
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index d7a3c63a2171..10916f6778ac 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -951,12 +951,28 @@ static struct sched_entity *__pick_eevdf(struct cfs_rq *cfs_rq)
> >       return NULL;
> >   }
> >
> > +/* Just simply choose the se with the smallest vruntime */
> > +static struct sched_entity *__pick_cfs(struct cfs_rq *cfs_rq)
> > +{
> > +     struct sched_entity *curr = cfs_rq->curr;
> > +     struct sched_entity *left = __pick_first_entity(cfs_rq);
> > +
> > +     /*
> > +      * If curr is set we have to see if its left of the leftmost entity
> > +      * still in the tree, provided there was anything in the tree at all.
> > +      */
> > +     if (!left || (curr && entity_before(curr, left)))
> > +             left = curr;
> > +
> > +     return left;
> > +}
> > +
> >   static struct sched_entity *pick_eevdf(struct cfs_rq *cfs_rq)
> >   {
> >       struct sched_entity *se = __pick_eevdf(cfs_rq);
> >
> >       if (!se) {
> > -             struct sched_entity *left = __pick_first_entity(cfs_rq);
> > +             struct sched_entity *left = __pick_cfs(cfs_rq);
> >               if (left) {
> >                       pr_err("EEVDF scheduling fail, picking leftmost\n");
> >                       return left;
Xuewen Yan Dec. 12, 2023, 2:51 a.m. UTC | #3 
Hi Abel

On Mon, Nov 20, 2023 at 4:49 PM Abel Wu <wuyun.abel@bytedance.com> wrote:
>
> Hi Xuewen, the pick part has been re-worked, would you please re-test
> with the newest branch?
>
> Thanks,
>         Abel
>
> https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/?h=sched%2Fcore

These patches would be merged into 6.6? If not, the pr_err also has a deadlock.
And should be changed to printk_deferred.


954 static struct sched_entity *pick_eevdf(struct cfs_rq *cfs_rq)
  955 {
  956         struct sched_entity *se = __pick_eevdf(cfs_rq);
  957
  958         if (!se) {
  959                 struct sched_entity *left = __pick_first_entity(cfs_rq);
  960                 if (left) {
  961                         pr_err("EEVDF scheduling fail, picking
leftmost\n"); <<<<
  962                         return left;
  963                 }
  964         }
  965
  966         return se;
  967 }


>
> On 11/20/23 3:38 PM, Xuewen Yan Wrote:
> > Now in pick_eevdf function, add the pick_first_entity to prevent
> > picking null when using eevdf, however, the leftmost may be null.
> > As a result, it would cause oops because the se is NULL.
> >
> > Fix this by compare the curr and left, if the left is null, set
> > the se be curr.
> >
> > Fixes: 147f3efaa241 ("sched/fair: Implement an EEVDF-like scheduling policy")
> > Signed-off-by: Xuewen Yan <xuewen.yan@unisoc.com>
> > ---
> >   kernel/sched/fair.c | 18 +++++++++++++++++-
> >   1 file changed, 17 insertions(+), 1 deletion(-)
> >
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index d7a3c63a2171..10916f6778ac 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -951,12 +951,28 @@ static struct sched_entity *__pick_eevdf(struct cfs_rq *cfs_rq)
> >       return NULL;
> >   }
> >
> > +/* Just simply choose the se with the smallest vruntime */
> > +static struct sched_entity *__pick_cfs(struct cfs_rq *cfs_rq)
> > +{
> > +     struct sched_entity *curr = cfs_rq->curr;
> > +     struct sched_entity *left = __pick_first_entity(cfs_rq);
> > +
> > +     /*
> > +      * If curr is set we have to see if its left of the leftmost entity
> > +      * still in the tree, provided there was anything in the tree at all.
> > +      */
> > +     if (!left || (curr && entity_before(curr, left)))
> > +             left = curr;
> > +
> > +     return left;
> > +}
> > +
> >   static struct sched_entity *pick_eevdf(struct cfs_rq *cfs_rq)
> >   {
> >       struct sched_entity *se = __pick_eevdf(cfs_rq);
> >
> >       if (!se) {
> > -             struct sched_entity *left = __pick_first_entity(cfs_rq);
> > +             struct sched_entity *left = __pick_cfs(cfs_rq);
> >               if (left) {
> >                       pr_err("EEVDF scheduling fail, picking leftmost\n");
> >                       return left;
Abel Wu Dec. 12, 2023, 3:17 a.m. UTC | #4 
On 12/12/23 10:51 AM, Xuewen Yan Wrote:
> Hi Abel
> 
> On Mon, Nov 20, 2023 at 4:49 PM Abel Wu <wuyun.abel@bytedance.com> wrote:
>>
>> Hi Xuewen, the pick part has been re-worked, would you please re-test
>> with the newest branch?
>>
>> Thanks,
>>          Abel
>>
>> https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/?h=sched%2Fcore
> 
> These patches would be merged into 6.6? If not, the pr_err also has a deadlock.
> And should be changed to printk_deferred.

Yes, they will be merged in Linus's tree.

> 
> 
> 954 static struct sched_entity *pick_eevdf(struct cfs_rq *cfs_rq)
>    955 {
>    956         struct sched_entity *se = __pick_eevdf(cfs_rq);
>    957
>    958         if (!se) {
>    959                 struct sched_entity *left = __pick_first_entity(cfs_rq);
>    960                 if (left) {
>    961                         pr_err("EEVDF scheduling fail, picking
> leftmost\n"); <<<<
>    962                         return left;
>    963                 }
>    964         }
>    965
>    966         return se;
>    967 }
> 
> 
>>
>> On 11/20/23 3:38 PM, Xuewen Yan Wrote:
>>> Now in pick_eevdf function, add the pick_first_entity to prevent
>>> picking null when using eevdf, however, the leftmost may be null.
>>> As a result, it would cause oops because the se is NULL.
>>>
>>> Fix this by compare the curr and left, if the left is null, set
>>> the se be curr.
>>>
>>> Fixes: 147f3efaa241 ("sched/fair: Implement an EEVDF-like scheduling policy")
>>> Signed-off-by: Xuewen Yan <xuewen.yan@unisoc.com>
>>> ---
>>>    kernel/sched/fair.c | 18 +++++++++++++++++-
>>>    1 file changed, 17 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
>>> index d7a3c63a2171..10916f6778ac 100644
>>> --- a/kernel/sched/fair.c
>>> +++ b/kernel/sched/fair.c
>>> @@ -951,12 +951,28 @@ static struct sched_entity *__pick_eevdf(struct cfs_rq *cfs_rq)
>>>        return NULL;
>>>    }
>>>
>>> +/* Just simply choose the se with the smallest vruntime */
>>> +static struct sched_entity *__pick_cfs(struct cfs_rq *cfs_rq)
>>> +{
>>> +     struct sched_entity *curr = cfs_rq->curr;
>>> +     struct sched_entity *left = __pick_first_entity(cfs_rq);
>>> +
>>> +     /*
>>> +      * If curr is set we have to see if its left of the leftmost entity
>>> +      * still in the tree, provided there was anything in the tree at all.
>>> +      */
>>> +     if (!left || (curr && entity_before(curr, left)))
>>> +             left = curr;
>>> +
>>> +     return left;
>>> +}
>>> +
>>>    static struct sched_entity *pick_eevdf(struct cfs_rq *cfs_rq)
>>>    {
>>>        struct sched_entity *se = __pick_eevdf(cfs_rq);
>>>
>>>        if (!se) {
>>> -             struct sched_entity *left = __pick_first_entity(cfs_rq);
>>> +             struct sched_entity *left = __pick_cfs(cfs_rq);
>>>                if (left) {
>>>                        pr_err("EEVDF scheduling fail, picking leftmost\n");
>>>                        return left;
diff mbox series

Patch

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index d7a3c63a2171..10916f6778ac 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -951,12 +951,28 @@  static struct sched_entity *__pick_eevdf(struct cfs_rq *cfs_rq)
 	return NULL;
 }
 
+/* Just simply choose the se with the smallest vruntime */
+static struct sched_entity *__pick_cfs(struct cfs_rq *cfs_rq)
+{
+	struct sched_entity *curr = cfs_rq->curr;
+	struct sched_entity *left = __pick_first_entity(cfs_rq);
+
+	/*
+	 * If curr is set we have to see if its left of the leftmost entity
+	 * still in the tree, provided there was anything in the tree at all.
+	 */
+	if (!left || (curr && entity_before(curr, left)))
+		left = curr;
+
+	return left;
+}
+
 static struct sched_entity *pick_eevdf(struct cfs_rq *cfs_rq)
 {
 	struct sched_entity *se = __pick_eevdf(cfs_rq);
 
 	if (!se) {
-		struct sched_entity *left = __pick_first_entity(cfs_rq);
+		struct sched_entity *left = __pick_cfs(cfs_rq);
 		if (left) {
 			pr_err("EEVDF scheduling fail, picking leftmost\n");
 			return left;