linux-kernel - Re: disabling secondary CPU hangs / system fails to suspend with kernel 4.19+

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Date:   Fri, 15 Mar 2019 12:41:00 +0100
From:   Thomas Müller <thomas@...htm.de>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: disabling secondary CPU hangs / system fails to suspend with
 kernel 4.19+

Hi,

Am 15.03.19 um 10:09 schrieb Peter Zijlstra:
> On Thu, Mar 14, 2019 at 04:17:28PM +0100, Thomas Müller wrote:
>> Hi,
>>
>> starting with kernel 4.19 my Lenovo ThinkPad X1 Carbon 5th no longer properly suspends.
>>
>> This is 100% reproducible and git bisect points to the following commit:
>>> [be45bf5395e0886a93fc816bbe41a008ec2e42e2] watchdog/softlockup: Fix cpu_stop_queue_work() double-queue bug
>>> be45bf5395e0886a93fc816bbe41a008ec2e42e2 is the first bad commit
>>> commit be45bf5395e0886a93fc816bbe41a008ec2e42e2
>>> Author: Peter Zijlstra <peterz@...radead.org>
>>> Date:   Fri Jul 13 12:42:08 2018 +0200
>>>
>>>     watchdog/softlockup: Fix cpu_stop_queue_work() double-queue bug
>>>     
>>>     When scheduling is delayed for longer than the softlockup interrupt
>>>     period it is possible to double-queue the cpu_stop_work, causing list
>>>     corruption.
>>>     
>>>     Cure this by adding a completion to track the cpu_stop_work's
>>>     progress.
>>>     
>>>     Reported-by: kernel test robot <lkp@...el.com>
>>>     Tested-by: Rong Chen <rong.a.chen@...el.com>
>>>     Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
>>>     Cc: Linus Torvalds <torvalds@...ux-foundation.org>
>>>     Cc: Peter Zijlstra <peterz@...radead.org>
>>>     Cc: Thomas Gleixner <tglx@...utronix.de>
>>>     Fixes: 9cf57731b63e ("watchdog/softlockup: Replace "watchdog/%u" threads with cpu_stop_work")
>>>     Link: http://lkml.kernel.org/r/20180713104208.GW2494@hirez.programming.kicks-ass.net
>>>     Signed-off-by: Ingo Molnar <mingo@...nel.org>
>>>
>>> :040000 040000 6aca2dbb84bc33fe442b18b3d0a135c27adff7b9 2710af12d32e4b98df07768716689b213bce45fc M      kernel
>>
>> The bugzilla reports have some additional details:
>> * https://bugzilla.redhat.com/show_bug.cgi?id=1671504
>> * https://bugzilla.kernel.org/show_bug.cgi?id=202679
>> * https://bugzilla.kernel.org/show_bug.cgi?id=202137
>>
>> I'm happy to provide additional information or test a patch or two (as long as it doesn't
>> eat up my notebook ;))
> 
> I obviously cannot reproduce :/ Both cpu-hotplug and suspend works just
> fine on my test boxes. I even tried my thinkpad (x240) and that too goes
> to sleep and wakes up just fine.
> 
> What .config do you have?
The one packaged by Fedora. I've attached the one for 4.20.15 as reference.

> And what, if anything do you see on the
> console when it goes funny?
Nothing unfortunately.
When trying to suspend the display immediately goes blank, the system becomes unresponsive and the
status LED within the power button start flashing rapidly (just like it does when the power cord is
attached).


> I think you wrote that hot-un-plug never completes? Is there anything in
> dmesg when it's stuck in:
> 
>   echo 0 > /sys/devices/system/cpu/cpu1/online
> 
> ?
I've just tried that again and the system immediately froze.
`journalctl -f` was running in a second window but it had no chance to output anything... :/


Best regards
Thomas

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