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From: Tejun Heo <tj@kernel.org>
To: Kang Chen <k.chen@smail.nju.edu.cn>
Cc: David Vernet <void@manifault.com>,
	Andrea Righi <arighi@nvidia.com>,
	Changwoo Min <changwoo@igalia.com>,
	sched-ext@lists.linux.dev, linux-kernel@vger.kernel.org,
	bpf@vger.kernel.org
Subject: Re: [PATCH sched_ext v2 1/2] sched_ext: make DSQ iterator stay drained after NULL
Date: Fri, 13 Nov 2026 09:50:59 -1000	[thread overview]
Message-ID: <2a1f54ec70384b99add9987a462b2052@kernel.org> (raw)
In-Reply-To: <20261113024505.922854-1-k.chen@smail.nju.edu.cn>

Hello, Kang.

v1 is already applied to sched_ext/for-7.4-fixes.

The selftest doesn't catch the bug reliably. Every ops.dequeue() invocation
overwrites next_after_drain and the test reads it once at the end. If the
last invocation saw an empty DSQ, the restarted walk returns NULL too and
the test passes on a kernel without the fix. Here, it passed about half of
the runs on an idle VM without the fix.

Also, I don't think the selftest is all that useful.

Thanks.

--
tejun

      parent reply	other threads:[~2026-11-13 19:51 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-11-10 12:51 [PATCH] " Kang Chen
2026-11-10 19:37 ` Tejun Heo
2026-11-13  2:45 ` [PATCH sched_ext v2 1/2] " Kang Chen
2026-11-13  2:45   ` [PATCH sched_ext v2 2/2] selftests/sched_ext: check that a drained DSQ iterator stays NULL Kang Chen
2026-11-13 19:50   ` Tejun Heo [this message]

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