linux-kernel - Shutdown-time hangs in -next in locktorture

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Message-ID: <7f63c3aa-5cf7-47a6-bdd9-d16d9ea65c63@paulmck-laptop>
Date: Fri, 19 Dec 2025 16:29:26 -0800
From: "Paul E. McKenney" <paulmck@...nel.org>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
	linux-next@...r.kernel.org, Stephen Rothwell <sfr@...b.auug.org.au>,
	Mark Brown <broonie@...nel.org>, kernel-team@...a.com
Subject: Shutdown-time hangs in -next in locktorture

Hello, Peter,

I started hitting shutdown-time hangs in next-20251217 which persist
in next-20251219.  This hang happens on both x86 and arm64.  Once I
figured out that the failure is high probability, but not deterministic,
bisection converged here:

5d1f0b2f278e ("sched/core: Rework sched_class::wakeup_preempt() and rq_modified_*()")

This commit reverts cleanly, and doing so restores hang-free operation.

The reproducer is shown below.

Thoughts?

							Thanx, Paul

------------------------------------------------------------------------

for i in 1 2 3 4 5
do
	tools/testing/selftests/rcutorture/bin/torture.sh --duration 20 --do-none --do-normal --do-locktorture --do-kasan --configs-locktorture "LOCK09"
	ret=$?
	if test "$ret" -ne 0
	then
		exit "$ret"
	fi
	echo Test $i succeeded
done
exit 0