linux-kernel - Re: [tip:timers/urgent] [timers/migration] 8cdb61838e: WARNING:at_kernel/time/timer_migration.c:#tmigr_connect_child

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Message-ID: <87ikx53i0g.fsf@somnus>
Date: Tue, 16 Jul 2024 09:36:47 +0200
From: Anna-Maria Behnsen <anna-maria@...utronix.de>
To: paulmck@...nel.org, kernel test robot <oliver.sang@...el.com>
Cc: oe-lkp@...ts.linux.dev, lkp@...el.com, linux-kernel@...r.kernel.org,
 x86@...nel.org, Thomas Gleixner <tglx@...utronix.de>, Frederic Weisbecker
 <frederic@...nel.org>
Subject: Re: [tip:timers/urgent] [timers/migration]  8cdb61838e:
 WARNING:at_kernel/time/timer_migration.c:#tmigr_connect_child_parent

Hi Paul,

"Paul E. McKenney" <paulmck@...nel.org> writes:

> On Wed, Jul 10, 2024 at 04:37:00PM +0800, kernel test robot wrote:
>> 
>> 
>> Hello,
>> 
>> kernel test robot noticed "WARNING:at_kernel/time/timer_migration.c:#tmigr_connect_child_parent" on:
>> 
>> commit: 8cdb61838ee5c63556773ea2eed24deab6b15257 ("timers/migration: Move hierarchy setup into cpuhotplug prepare callback")
>> https://git.kernel.org/cgit/linux/kernel/git/tip/tip.git timers/urgent
>
> For whatever it is worth, I am also seeing this on refscale runs on
> recent -next.
>
> The reproducer is to clone perfbook [1] in your ~/git directory
> (as in ~/git/perfboot), then run this from your Linux source tree,
> preferably on a system with few CPUs:
>
> bash ~/git/perfbook/CodeSamples/defer/rcuscale.sh
>
> The output will have "FAIL" in it, which indicates that the corresponding
> guest OS splatted.  If it would be useful, I would be happy to produce
> a one-liner that runs the guest OS only once and leaves the console
> output around.  Otherwise, I will continue being lazy.  ;-)

Thanks for the report. I found the root cause for it and I am working on
a fix as the commit which triggers the warning also has another
problem... And I already requested to drop the tip timers/urgent patches
(at least my patches).

So, enjoy being lazy!

Thanks,

	Anna-Maria