Re: [PATCH v25 1/9] sched: Make class_schedulers avoid pushing current, and get rid of proxy_tag_curr()

[K Prateek Nayak]

Hello John,

On 3/17/2026 11:34 AM, John Stultz wrote:
> On Mon, Mar 16, 2026 at 10:41 PM K Prateek Nayak <kprateek.nayak@xxxxxxx> wrote:
>> On 3/17/2026 10:19 AM, John Stultz wrote:
>>>
>>> I guess adding a new helper function to manually do the
>>> put_prev/set_next could be added to the top level __schedule() logic
>>> in the (prev != next) case, though we'll have to preserve the
>>> prev_donor on the stack probably.
>>
>> That seems like the best option to me too.
>>
>> Also, deadline, RT, fair, and idle don't really care about the "next"
>> argument of put_prev_task() and the only one that does care is
>> put_prev_task_scx() to call switch_class() callback so putting it as
>> either NULL or "rq->donor" should be safe.
> 
> Ack.
> Here's the change I'm testing tonight (against 6.18):
> https://github.com/johnstultz-work/linux-dev/commit/0cc72a4923143f496e33711cbcc1afdf6d861ca6

Thanks a ton for pushing out to WIP! Only nit. would be a:

  s/rq->donor/prev_donor/

on the lines with {put_prev/set_next}_task() to save on the
additional dereference since they are both the same (but maybe
the complier figures that out on its own?)

Also would a sched_proxy_exec() check within that function
make sense to skip evaluation of that branch entirely when
proxy exec is disabled via cmdline?

> Feel free to suggest a better name for the helper function. It feels a
> little clunky (and sort of sad right after getting rid of the clunky
> proxy_tag_curr(), to re-add something so similar).

I know and I'm sorry about that (T_T)

-- 
Thanks and Regards,
Prateek