Re: [PATCH 1/2] sched_ext: Fix ops.dequeue() semantics

[Andrea Righi]

On Wed, Feb 11, 2026 at 12:37:13PM -1000, Tejun Heo wrote:
> Hello,
> 
> On Wed, Feb 11, 2026 at 11:34:54PM +0100, Andrea Righi wrote:
> > > The end result is about the same because whenever we migrate we're sending
> > > it to the local DSQ of the destination CPU, so whether we generate the event
> > > on deactivation of the source CPU or activation on the destination doesn't
> > > make *whole* lot of difference. However, conceptually, migrations are
> > > internal events. There isn't anything actionable for the BPF scheduler. The
> > > reason why ops.dequeue() should be emitted is not because the task is
> > > changing CPUs (which caused the deactivation) but the fact that it ends up
> > > in a local DSQ afterwards. I think it'll be cleaner both conceptually and
> > > code-wise to emit ops.dequeue() only from dispatch_enqueue() and dequeue
> > > paths.
> > 
> > Does this include core scheduler migrations or just SCX-initiated
> > migrations (move_remote_task_to_local_dsq())?
> > 
> > Because with core scheduler migrations we trigger ops.enqueue(), so we
> > should also trigger ops.dequeue(). Or we need to send the task straight to
> > local to prevent calling ops.enqueue().
> 
> I'm a bit lost. Can you elaborate on core scheduler migrations triggering
> ops.enqueue()?

Nevermind, just ignore that comment, we clearly want to trigger
ops.dequeue/enqueue() in that case, it's the whole point of
SCX_DEQ_SCHED_CHANGE. I should probably go to bed and get some sleep. :)

-Andrea