linux-kernel - Re: Linux 5.14

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Message-ID: <8735qqfpv4.ffs@tglx>
Date:   Tue, 31 Aug 2021 01:57:03 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Guenter Roeck <linux@...ck-us.net>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-s390@...r.kernel.org, Heiko Carstens <hca@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>
Subject: Re: Linux 5.14

On Mon, Aug 30 2021 at 22:32, Thomas Gleixner wrote:

> On Mon, Aug 30 2021 at 13:12, Guenter Roeck wrote:
>> On Sun, Aug 29, 2021 at 03:19:23PM -0700, Linus Torvalds wrote:
>> So far so good, but there is a brand new runtime warning, seen when booting
>> s390 images.
>>
>> [    3.218816] ------------[ cut here ]------------
>> [    3.219010] WARNING: CPU: 1 PID: 0 at kernel/sched/core.c:5779 sched_core_cpu_starting+0x172/0x180
>> [    3.222992]  [<0000000000186e86>] sched_core_cpu_starting+0x176/0x180
>> [    3.223114] ([<0000000000186dc4>] sched_core_cpu_starting+0xb4/0x180)
>> [    3.223182]  [<00000000001963e4>] sched_cpu_starting+0x2c/0x68
>> [    3.223243]  [<000000000014f288>] cpuhp_invoke_callback+0x318/0x970
>> [    3.223304]  [<000000000014f970>] cpuhp_invoke_callback_range+0x90/0x108
>> [    3.223364]  [<000000000015123c>] notify_cpu_starting+0x84/0xa8
>> [    3.223426]  [<0000000000117bca>] smp_init_secondary+0x72/0xf0
>> [    3.223492]  [<0000000000117846>] smp_start_secondary+0x86/0x90
>>
>> Commit 3c474b3239f12 ("sched: Fix Core-wide rq->lock for uninitialized
>> CPUs") sems to be the culprit. Indeed, the warning is gone after reverting
>> this commit.
>
> The warning is gone, but the underlying S390 problem persists:
>
> S390 invokes notify_cpu_starting() _before_ updating the topology masks.

And interestingly enough that very commit was tested on S390:

  https://lore.kernel.org/r/yt9dy28o8q0o.fsf@linux.ibm.com

Thanks,

        tglx