Re: [PATCH] sched: update the rq->avg_idle when a task is moved to an idle CPU

[Shijie Huang]

On 25/11/2025 18:02, Madadi Vineeth Reddy wrote:
> IIUC, update_rq_avg_idle() already checks if (rq->idle_stamp) internally and
> in attach_task() we have rq available and the guard in update_rq_avg_idle()
> ensures we only update when the CPU was actually idle. Whether it's called
> during newidle, idle, or busy balancing shouldn't matter.

In the newidle function:

   sched_balance_newidle():

            ...............................

            this_rq->idle_stamp = rq_clock(this_rq);        // step 1

             sched_balance_rq() ---> ... --> attach_task()        // step 2

            if (pulled_task)

                    this_rq->idle_stamp = 0;                // step 3

             .............................................


         If update_rq_avg_idle() is called in attach_task() in "step 
2", it will mess up the "step 1".

The update_rq_avg_idle() should be called after "step 3".

Thanks

Huang Shijie