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SubjectRe: [PATCH] sched: Fix balance_push() vs __sched_setscheduler()
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Hi Peter


On Tue, 2022-06-07 at 23:39 +0200, Peter Zijlstra wrote:
> On Tue, Jun 07, 2022 at 10:40:36PM +0200, Peter Zijlstra wrote:
> > On Fri, Jun 03, 2022 at 12:15:51AM +0800, Jing-Ting Wu wrote:
> > > The patch is helpful to the syndrome, passed stability test over
> > > 10
> > > days so far. (as-is: < 48 hours failed)
> >
> > Excellent, let me go write a Changelog for it, or something.
>
> How's this then?

I think the description is fine.
Thanks for your help.

[...]
>
> -static inline struct callback_head *splice_balance_callbacks(struct
> rq *rq)
> +static inline struct callback_head *
> +__splice_balance_callbacks(struct rq *rq, bool split)
> {
> struct callback_head *head = rq->balance_callback;
>
> + if (likely(!head))
> + return NULL;
> +
> lockdep_assert_rq_held(rq);
> - if (head)
> + /*
> + * Must not take balance_push_callback off the list when
> + * splace_balance_callbac() and balance_callbacks() are not


Should we change splace_balance_callbac() to splice_balance_callbacks()
at here?


> + * in the same rq->lock section.
> + *
> + * In that case it would be possible for __schedule() to
> interleave
> + * and observe the list empty.
> + */
> + if (split && head == &balance_push_callback)
> + head = NULL;
> + else
> rq->balance_callback = NULL;
>
> return head;
> }
>
[...]


Best Regards,
Jing-Ting Wu

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