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SubjectRe: [PATCH] sched/eevdf: Avoid NULL in pick_eevdf
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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;

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