linux-kernel - sched/core warning triggers on rcu torture test

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Date:   Tue, 26 Jun 2018 18:16:04 +0200 (CEST)
From:   Anna-Maria Gleixner <anna-maria@...utronix.de>
To:     linux-kernel@...r.kernel.org
cc:     "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: sched/core warning triggers on rcu torture test

Hi,

during rcu torture tests (TREE04 and TREE07) I noticed, that a
WARN_ON_ONCE() in sched core triggers on a recent 4.18-rc2 based
kernel (6f0d349d922b ("Merge
git://git.kernel.org/pub/scm/linux/kernel/git/davem/net")) as well as
on a 4.17.3.

I'm running the tests on a machine with 144 cores:

  tools/testing/selftests/rcutorture/bin/kvm.sh --cpus 144 --duration 120 --configs "9*TREE07"
  tools/testing/selftests/rcutorture/bin/kvm.sh --cpus 144 --duration 120 --configs "18*TREE04"


The warning was introduced by commit d84b31313ef8 ("sched/isolation:
Offload residual 1Hz scheduler tick").


Output looks similar for all tests I did (this one is the output of
the 4.18-rc2 based kernel):

WARNING: CPU: 11 PID: 906 at kernel/sched/core.c:3138 sched_tick_remote+0xb6/0xc0
Modules linked in:
CPU: 11 PID: 906 Comm: kworker/u32:3 Not tainted 4.18.0-rc2+ #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
Workqueue: events_unbound sched_tick_remote
RIP: 0010:sched_tick_remote+0xb6/0xc0
Code: e8 0f 06 b8 00 c6 03 00 fb eb 9d 8b 43 04 85 c0 75 8d 48 8b 83 e0 0a 00 00 48 85 c0 75 81 eb 88 48 89 df e8 bc fe ff ff eb aa <0f> 0b eb c5 66 0f 1f 44 00 00 bf 17 00 00 00 e8 b6 2e fe ff 0f b6
Call Trace:
 process_one_work+0x1df/0x3b0
 worker_thread+0x44/0x3d0
 kthread+0xf3/0x130
 ? set_worker_desc+0xb0/0xb0
 ? kthread_create_worker_on_cpu+0x70/0x70
 ret_from_fork+0x35/0x40
---[ end trace 7c99b83eb0ec64e8 ]---


Do you need some more information?


Thanks,

	Anna-Maria