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

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Message-ID: <aVK3lEn-x6EA86Qo@gpd4>
Date: Mon, 29 Dec 2025 18:17:08 +0100
From: Andrea Righi <arighi@...dia.com>
To: Tejun Heo <tj@...nel.org>
Cc: David Vernet <void@...ifault.com>, Changwoo Min <changwoo@...lia.com>,
	Emil Tsalapatis <emil@...alapatis.com>,
	Daniel Hodges <hodgesd@...a.com>, sched-ext@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] sched_ext: Fix ops.dequeue() semantics

Hi,

On Sun, Dec 28, 2025 at 01:42:28PM -1000, Tejun Heo wrote:
> Hello,
> 
> On Fri, Dec 19, 2025 at 11:43:14PM +0100, Andrea Righi wrote:
> > +   Once ``ops.enqueue()`` is called, the task is considered "enqueued" and
> > +   is owned by the BPF scheduler. Ownership is retained until the task is
> 
> Can we avoid using "ownership" for this? From user's POV, this is fine but
> kernel side internally uses the word for different purposes - e.g. we say
> the BPF side owns the task if the task's SCX_OPSS_QUEUED is set (ie. it's on
> BPF data structure, not on a DSQ). Here, the ownership encompasses both
> kernel-side and BPF-side queueing, so the term becomes rather confusing.
> Maybe we can stick with "queued" or "enqueued"?

Agreed. I can't find a better term to describe this phase of the lifecycle,
where ops.enqueue() has been called and the task remains in that state
until the corresponding ops.dequeue() occurs (either due to a "dispatch"
dequeue or "real" dequeue).

So maybe we should stick with "enqueued" and clarify exactly what this
state means.

Thanks,
-Andrea