2023-11-20 07:39:13

by Xuewen Yan

Subject: [PATCH] sched/eevdf: Avoid NULL in pick_eevdf

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 <[email protected]>
---
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;
--
2.25.1

2023-11-20 08:49:52

by Abel Wu

Subject: Re: [PATCH] sched/eevdf: Avoid NULL in pick_eevdf

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 <[email protected]>
> ---
> 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;

2023-11-21 05:09:29

by Xuewen Yan

Subject: Re: [PATCH] sched/eevdf: Avoid NULL in pick_eevdf

On Mon, Nov 20, 2023 at 4:49 PM Abel Wu <[email protected]> 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 <[email protected]>
> > ---
> > 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;

2023-12-12 02:51:29

by Xuewen Yan

Subject: Re: [PATCH] sched/eevdf: Avoid NULL in pick_eevdf

Hi Abel

On Mon, Nov 20, 2023 at 4:49 PM Abel Wu <[email protected]> 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 <[email protected]>
> > ---
> > 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;

2023-12-12 03:18:13

by Abel Wu

Subject: Re: Re: [PATCH] sched/eevdf: Avoid NULL in pick_eevdf

On 12/12/23 10:51 AM, Xuewen Yan Wrote:
> Hi Abel
>
> On Mon, Nov 20, 2023 at 4:49 PM Abel Wu <[email protected]> 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 <[email protected]>
>>> ---
>>> 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;