From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <dietmar.eggemann@arm.com>
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on gnuweeb.org
X-Spam-Level: 
X-Spam-Status: No, score=-6.0 required=5.0 tests=NICE_REPLY_A,RCVD_IN_DNSWL_HI,
	SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6
Received: from foss.arm.com (foss.arm.com [217.140.110.172])
	by gnuweeb.org (Postfix) with ESMTP id E0C1B7E375
	for <gwml@vger.gnuweeb.org>; Tue,  5 Apr 2022 12:21:14 +0000 (UTC)
Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14])
	by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 08866D6E;
	Tue,  5 Apr 2022 05:21:14 -0700 (PDT)
Received: from [192.168.178.6] (unknown [172.31.20.19])
	by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2881B3F5A1;
	Tue,  5 Apr 2022 05:21:12 -0700 (PDT)
Message-ID: <f71d132d-02a0-918c-ab2b-3234d0d492a4@arm.com>
Date: Tue, 5 Apr 2022 14:21:10 +0200
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101
 Thunderbird/91.5.0
Subject: Re: [Linux 5.18-rc1] WARNING: CPU: 1 PID: 0 at
 kernel/sched/fair.c:3355 update_blocked_averages
Content-Language: en-US
To: Ammar Faizi <ammarfaizi2@gnuweeb.org>,
 Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Cc: Ben Segall <bsegall@google.com>,
 Daniel Bristot de Oliveira <bristot@redhat.com>,
 GNU/Weeb Mailing List <gwml@vger.gnuweeb.org>, Ingo Molnar
 <mingo@redhat.com>, Juri Lelli <juri.lelli@redhat.com>,
 Mel Gorman <mgorman@suse.de>, Peter Zijlstra <peterz@infradead.org>,
 Steven Rostedt <rostedt@goodmis.org>,
 Vincent Guittot <vincent.guittot@linaro.org>
References: <b86541ea-7d96-5a24-1b65-37c24c70d3ff@gnuweeb.org>
From: Dietmar Eggemann <dietmar.eggemann@arm.com>
In-Reply-To: <b86541ea-7d96-5a24-1b65-37c24c70d3ff@gnuweeb.org>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
List-Id: <gwml.vger.gnuweeb.org>

On 04/04/2022 08:19, Ammar Faizi wrote:
> 
> Hello scheduler maintainers,
> 
> I got the following warning in Linux 5.18-rc1, I don't have the
> reproducer yet,
> it happens randomly. Please shed some light.

Tried to recreate the issue but no success so far. I used you config
file, clang-14 and a Xeon CPU E5-2690 v2 (2 sockets 40 CPUs) with 20
two-level cgoupv1 taskgroups '/X/Y' with 'hackbench (10 groups, 40 fds)
+ idling' running in all '/X/Y/'.

What userspace are you running?

There seemed to be some pressure on your machine when it happened?

> <6>[13420.623334][    C7] perf: interrupt took too long (2530 > 2500),
> lowering kernel.perf_event_max_sample_rate to 78900

Maybe you could split the SCHED_WARN_ON so we know which signal causes this?

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index d4bd299d67ab..0d45e09e5bfc 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3350,9 +3350,9 @@ static inline bool cfs_rq_is_decayed(struct cfs_rq
*cfs_rq)
         * Make sure that rounding and/or propagation of PELT values never
         * break this.
         */
-       SCHED_WARN_ON(cfs_rq->avg.load_avg ||
-                     cfs_rq->avg.util_avg ||
-                     cfs_rq->avg.runnable_avg);
+       SCHED_WARN_ON(cfs_rq->avg.load_avg);
+       SCHED_WARN_ON(cfs_rq->avg.util_avg);
+       SCHED_WARN_ON(cfs_rq->avg.runnable_avg);

        return true;
 }

[...]