linux-kernel - Re: [PATCH] sched_ext: Invalidate dispatch decisions on CPU affinity changes

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Message-ID: <aYPvOXyGJTyHV-eY@slm.duckdns.org>
Date: Wed, 4 Feb 2026 15:15:37 -1000
From: Tejun Heo <tj@...nel.org>
To: Andrea Righi <arighi@...dia.com>
Cc: David Vernet <void@...ifault.com>, Changwoo Min <changwoo@...lia.com>,
	Christian Loehle <christian.loehle@....com>,
	Emil Tsalapatis <emil@...alapatis.com>,
	Daniel Hodges <hodgesd@...a.com>, sched-ext@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched_ext: Invalidate dispatch decisions on CPU affinity
 changes

Hello,

On Wed, Feb 04, 2026 at 01:31:35PM -1000, Tejun Heo wrote:
...
> I wonder whether we should define an invalid qseq and use that instead. The
> queueing instance really is invalid after this and it would help catching
> cases where BPF scheduler makes mistakes w/ synchronization. Also, wouldn't
> dequeue_task_scx() or ops_dequeue() be a better place to shoot down the
> enqueued instances? While the symptom we most immediately see are through
> cpumask changes, the underlying problem is dequeue not shooting down
> existing enqueued tasks.

Hmmm... in fact, this is all happening already, right? Isn't all that's
missing the BPF scheduler's ops.dequeue() synchronizing against
scx_bpf_dsq_insert()?

Thanks.

-- 
tejun