linux-kernel - Re: [cpuidle,intel_idle] 32d4fd5751: WARNING:at_kernel/rcu/tree.c:#rcu_eqs

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Date:   Thu, 23 Jun 2022 11:23:59 +0000
From:   Shinichiro Kawasaki <shinichiro.kawasaki@....com>
To:     kernel test robot <oliver.sang@...el.com>
CC:     Peter Zijlstra <peterz@...radead.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        LKML <linux-kernel@...r.kernel.org>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "lkp@...ts.01.org" <lkp@...ts.01.org>,
        "lkp@...el.com" <lkp@...el.com>,
        Damien Le Moal <Damien.LeMoal@....com>
Subject: Re: [cpuidle,intel_idle]  32d4fd5751:
 WARNING:at_kernel/rcu/tree.c:#rcu_eqs_exit

On Jun 13, 2022 / 00:00, kernel test robot wrote:
> 
> 
> Greeting,
> 
> FYI, we noticed the following commit (built with gcc-11):
> 
> commit: 32d4fd5751eadbe1823a37eb38df85ec5c8e6207 ("cpuidle,intel_idle: Fix CPUIDLE_FLAG_IRQ_ENABLE")
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
> 
> in testcase: kernel-selftests
> version: kernel-selftests-x86_64-cef46213-1_20220609
> with following parameters:
> 
> 	group: resctrl
> 	ucode: 0x500320a
> 
> test-description: The kernel contains a set of "self tests" under the tools/testing/selftests/ directory. These are intended to be small unit tests to exercise individual code paths in the kernel.
> test-url: https://www.kernel.org/doc/Documentation/kselftest.txt
> 
> 
> on test machine: 88 threads 2 sockets Intel(R) Xeon(R) Gold 6238M CPU @ 2.10GHz with 128G memory
> 
> caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):
> 
> 
> 
> If you fix the issue, kindly add following tag
> Reported-by: kernel test robot <oliver.sang@...el.com>
> 
> 
> [ 29.104402][ T0] WARNING: CPU: 0 PID: 0 at kernel/rcu/tree.c:864 rcu_eqs_exit+0x4b/0xc0 
> [   29.104417][    T0]
> [   29.104418][    T0] =============================
> [   29.104419][    T0] WARNING: suspicious RCU usage
> [   29.104421][    T0] 5.19.0-rc1-00001-g32d4fd5751ea #1 Not tainted
> [   29.104424][    T0] -----------------------------

FYI, I observe this WARNING on my test servers for fstests, with kernel
v5.19-rc3. It was observed at system boot, and was also observed repeatedly
during fstests run. I reverted the commit 32d4fd5751ea then the WARNING
disappeared. The WARNING was observed on systems with 20 threads CPU, but
not observed on systems with 8 threads CPU.

Looking in the commit, I'm not sure how it is related to the RCU warning.
If any further action on my system would help, please let me know.

-- 
Shin'ichiro Kawasaki