linux-kernel - Re: [tip:sched/core] sched/core: Add debugging code to catch missing update_rq

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Date:   Tue, 31 Jan 2017 19:35:59 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Matt Fleming <matt@...eblueprint.co.uk>
Cc:     fweisbec@...il.com, tglx@...utronix.de, pmladek@...e.com,
        hpa@...or.com, efault@....de, sergey.senozhatsky.work@...il.com,
        peterz@...radead.org, mgorman@...hsingularity.net,
        wanpeng.li@...mail.com, umgwanakikbuti@...il.com,
        byungchul.park@....com, jack@...e.cz, mingo@...nel.org,
        riel@...hat.com, luca.abeni@...tn.it, yuyang.du@...el.com,
        torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org,
        linux-tip-commits@...r.kernel.org,
        "linuxppc-dev\@lists.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-next\@vger.kernel.org" <linux-next@...r.kernel.org>
Subject: Re: [tip:sched/core] sched/core: Add debugging code to catch missing update_rq_clock() calls

Matt Fleming <matt@...eblueprint.co.uk> writes:

> On Tue, 31 Jan, at 08:24:53AM, Michael Ellerman wrote:
>> 
>> I'm hitting this on multiple powerpc systems:
>> 
>> [   38.339126] rq->clock_update_flags < RQCF_ACT_SKIP
>> [   38.339134] ------------[ cut here ]------------
>> [   38.339142] WARNING: CPU: 2 PID: 1 at kernel/sched/sched.h:804 detach_task_cfs_rq+0xa0c/0xd10
>
> [...]
>  
>> I assume I should be worried?
>
> Thanks for the report. No need to worry, the bug has existed for a
> while, this patch just turns on the warning ;-)
>
> The following commit queued up in tip/sched/core should fix your
> issues (assuming you see the same callstack on all your powerpc
> machines):
>
>   https://git.kernel.org/cgit/linux/kernel/git/tip/tip.git/commit/?h=sched/core&id=1b1d62254df0fe42a711eb71948f915918987790

Great thanks.

Looks like that commit is in today's linux-next, so hopefully I won't
see any oopses in my boot tests overnight. If I do I'll let you know.

cheers