Re: [RFC PATCH 2/3] sched/core: Fix forceidle when lock owner has mismatchd cookie

[K Prateek Nayak]

Hello Jon,

On 7/23/2026 8:44 AM, John Stultz wrote:
> On Fri, Jul 17, 2026 at 4:17 AM K Prateek Nayak <kprateek.nayak@xxxxxxx> wrote:
>>
>> Move Vasily's fix from 7cd4088f70e0 ("sched/core: Don't proxy-exec
>> unmatched cookie lock owners") into a separate helper and fix the
>> forceidle stats, balance callback queuing when rq is not the one
>> dictating the core cookie.
>>
>> The helper will be extended in subsequent commits to allow for re-pick
>> with cookie from the lock owner if rq is the pick leader.
>>
>> Signed-off-by: K Prateek Nayak <kprateek.nayak@xxxxxxx>
> 
> Thanks again for sending these out. I've included these in my full
> proxy-exec-WIP tree and ran into a few build issues with this one.
> 
>> ---
>>  kernel/sched/core.c | 43 ++++++++++++++++++++++++++++++++++++-------
>>  1 file changed, 36 insertions(+), 7 deletions(-)
>>
>> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
>> index 31fa6bcee616..ed11410f1416 100644
>> --- a/kernel/sched/core.c
>> +++ b/kernel/sched/core.c
>> @@ -6598,6 +6598,8 @@ __pick_next_task(struct rq *rq, struct rq_flags *rf)
>>         BUG(); /* The idle class should always have a runnable task. */
>>  }
>>
>> +static void proxy_deactivate(struct rq *rq, struct task_struct *donor);
>> +
> 
> So this should probably go in a "#ifdef CONFIG_SCHED_PROXY_EXEC"
> block, or in the !SCHED_PROXY_EXEC case you get defined but not used
> warnings.
> 
> 
>> @@ -7113,6 +7132,18 @@ pick_next_task(struct rq *rq, struct rq_flags *rf)
>>         return __pick_next_task(rq, rf);
>>  }
>>
>> +static struct task_struct *
>> +sched_core_swap_pick(struct rq *rq, struct task_struct *next)
>> +{
>> +       /*
>> +        * Caller should always check !sched_cpu_cookie_match(rq, next)
>> +        * which is always false for !CONFIG_SCHED_CORE and execution
>> +        * should never reach here.
>> +        */
>> +       BUG_ON();
> 
> This should just be BUG()
> 
> I'll fold these fixes up into the patch in my tree, but wanted to give
> you a heads up should you intend to resend these out for review
> sooner.

Thanks a ton for fixing those! Guilty of not testing with
!CONFIG_SCHED_PROXY_EXEC. Will definitely make sure I at least test a
build next time around :-)

I'll wait for your next version and rebase on top of that.

-- 
Thanks and Regards,
Prateek