Re: [PATCH] sched: Proxy yields to donor tasks

[Fernand Sieber <sieberf@amazon.com>]

On Thu, Nov 07, 2025 at 02:31:16PM +0800, kernel test robot wrote:
> sparse warnings: (new ones prefixed by >>)
>
>>> kernel/sched/rt.c:529:55: sparse: warning: incorrect type in initializer (different address spaces)
>>> kernel/sched/rt.c:976:39: sparse: warning: incorrect type in initializer (different address spaces)

Thank you for the report.

The warnings occur because my patch changes scheduler yield functions from
accessing rq->curr to rq->donor, both of which have identical __rcu annotations.
These are pre-existing annotation issues in the scheduler code, which has been
directly accessing RCU-annotated pointers without proper dereferencing, relying
on runqueue lock protection instead.

If we do want to address these sparse warnings, I can make modifications like:

-               curr = rq->donor;
+               curr = rcu_dereference_protected(rq->donor, lockdep_is_held(&rq->__lock));

This would have zero runtime overhead while satisfying sparse's RCU checking.

Peter, let me know if these warnings should be addressed.

Thanks,
Fernand



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