Re: [PATCH v2 10/10] sched/eevdf: Move to a single runqueue

[K Prateek Nayak <kprateek.nayak@amd.com>]

Hello Peter,

On 5/26/2026 3:22 PM, Peter Zijlstra wrote:
> On Tue, May 26, 2026 at 02:45:45PM +0530, K Prateek Nayak wrote:
> 
>> The suggested diff above solves the crash in my case but your
>> mileage may vary. Peter can comment if this is the right thing
>> to do or not :-)
> 
> Is this a different issue than the one you raised before?

Yes, this is different. Essentially, this is what is happening:

  throttle_cfs_rq_work()
    task_rq_lock()

    dequeue_task_fair(current)    /* Task is dequeued on cfs side */
      __dequeue_task(current)
        dequeue_hierarchy(current);
          current->se.on_rq = 0;
          /* update_load_sub() */
    resched_curr();               /* Initiates a resched */

    task_rq_unlock()
      local_irq_enable();

  =====> sched_tick()
          task_tick_fair()
             __calc_prop_weight()
               /*
                * Oops: update_load_sub() above has
                * 0ed the weight of cfs_rq.
                */
  <====

  preempt_schedule_irq()
    next = ...
    put_prev_set_next_task() /* The runtime context is switched here */


> We talked about throtte, and you were going to make a proper patch of that cleanup
> iirc.

I had rebased your suggestion on tip and fixed a couple of splats but
once it was functional, I noticed hackbench taking twice as long to
complete compared to tip and I was chasing that before I fell sick.

Let me go dig deeper to see where exactly it is all going sideways.

-- 
Thanks and Regards,
Prateek