linux-kernel - Re: [PATCH] sched/fair: Fix inaccurate h_nr_runnable accounting with delayed dequeue

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Message-ID: <f2acd84b-a102-487a-b7c1-3ce1e85dee1f@amd.com>
Date: Mon, 20 Jan 2025 14:44:47 +0530
From: K Prateek Nayak <kprateek.nayak@....com>
To: Madadi Vineeth Reddy <vineethr@...ux.ibm.com>
CC: <bsegall@...gle.com>, <dietmar.eggemann@....com>,
	<gautham.shenoy@....com>, <juri.lelli@...hat.com>,
	<linux-kernel@...r.kernel.org>, <mgorman@...e.de>, <mingo@...hat.com>,
	<peterz@...radead.org>, <rostedt@...dmis.org>, <swapnil.sapkal@....com>,
	<vincent.guittot@...aro.org>, <vschneid@...hat.com>
Subject: Re: [PATCH] sched/fair: Fix inaccurate h_nr_runnable accounting with
 delayed dequeue

On 1/20/2025 2:14 PM, Madadi Vineeth Reddy wrote:
>> However, I was unable to trigger the WARN_ON by running hackbench in a
>> cgroup without the patch. Could you please share the specific test
>> scenario or configuration you used to reproduce it?
> 
> My mistake: SCHED_WARN_ON is a WARN_ONCE, so I had to clear it before
> running hackbench to ensure the WARN_ON could be triggered again.

Yup! A WARN_ON() is hit very consistently.

> 
> Now I am able to trigger the WARN_ON in the unpatched kernel while
> running hackbench after executing `echo 1 > /sys/kernel/debug/clear_warn_once`
> following the initial warning during the boot process. I have verified
> that the patched kernel fixes the issue.

Thank you again for testing the fix. Much appreciated!

> 
> Thanks,
> Madadi Vineeth Reddy

-- 
Thanks and Regards,
Prateek