Re: [PATCH] sched_ext: Hold DSQ refs for deferred reenqueues

[Tejun Heo]

On Thu, Oct 01, 2026 at 12:20:49AM +0900, Hui Su wrote:
> Please disregard this posting. This was intended to be v2, but I
> accidentally omitted the version tag.
> 
> I am preparing v3 to address the review feedback. In particular, it
> will serialize exit_dsq() with deferred detach/reference acquisition
> using deferred_reenq_lock, and keep final DSQ reclamation out of the
> deferred path while the rq raw spinlock is held.
> 
> The revised design keeps a single DSQ refcount and the existing
> rcu_head, without polling the refcount from repeated RCU callbacks.
> 
> I will post v3 after revalidation. Sorry for the confusion.

Can you try to do it without refcnts? DSQ destructions are rare events and
we can reliably detect whether the DSQ is full or not. I'd much rather make
the destruction path expensive than adding refcnt to hot paths.

Thanks.

-- 
tejun