linux-kernel - Re: INFO: rcu_preempt detected expedited stalls on CPUs/tasks (6.1.0-rc3): in cat /sys/kernel/debug/kmemleak #forregzbot

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Date:   Tue, 29 Nov 2022 09:53:57 +0100
From:   Thorsten Leemhuis <regressions@...mhuis.info>
To:     "regressions@...ts.linux.dev" <regressions@...ts.linux.dev>
Cc:     LKML <linux-kernel@...r.kernel.org>
Subject: Re: INFO: rcu_preempt detected expedited stalls on CPUs/tasks
 (6.1.0-rc3): in cat /sys/kernel/debug/kmemleak #forregzbot

On 09.11.22 11:48, Thorsten Leemhuis wrote:
> [Note: this mail is primarily send for documentation purposes and/or for
> regzbot, my Linux kernel regression tracking bot. That's why I removed
> most or all folks from the list of recipients, but left any that looked
> like a mailing lists. These mails usually contain '#forregzbot' in the
> subject, to make them easy to spot and filter out.]
>
> On 04.11.22 23:01, Mirsad Goran Todorovac wrote:
>>
>> When investigating thermald kmemleak, it occurred that the "cat
>> /sys/kernel/debug/kmemleak"
>> and "tail -20 /sys/kernel/debug/kmemleak" commands take unusual amount
>> of time.
>>
>> Dmesg output showed expedited stalls that the commands caused NMIs and
>> NMI backtraces:
>>
>> [ 8123.263464] rcu: INFO: rcu_preempt detected expedited stalls on
>> CPUs/tasks: { 0-.... } 26 jiffies s: 3829 root: 0x1/.
>> [ 8123.263500] rcu: blocking rcu_node structures (internal RCU debug):
>> [ 8123.263508] Sending NMI from CPU 7 to CPUs 0:
>> [ 8123.263528] NMI backtrace for cpu 0
>> [ 8123.263539] CPU: 0 PID: 27898 Comm: cat Not tainted 6.1.0-rc3 #1
>> [ 8123.263552] Hardware name: LENOVO 82H8/LNVNB161216, BIOS GGCN34WW
>> 03/08/2022
> 
> #regzbot ^introduced 28b3ae426598e
> #regzbot title rcu: thermald causes a kmemleak
> #regzbot ignore-activity

#regzbot invalid: likely not a regression and just a odd config

For details see the discussion ending here:
https://lore.kernel.org/all/20221124201552.GV4001@paulmck-ThinkPad-P17-Gen-1/

Ciao, Thorsten