Groups > linux.kernel > #1620540

Re: WARN @lib/refcount.c:128 during hot unplug of I/O adapter.

From	Tyrel Datwyler <tyreld@linux.vnet.ibm.com>
Newsgroups	linux.kernel
Subject	Re: WARN @lib/refcount.c:128 during hot unplug of I/O adapter.
Date	2017-04-10 20:00 +0200
Message-ID	<tuLLA-3YK-19@gated-at.bofh.it> (permalink)
References	<ttcPV-7fO-23@gated-at.bofh.it> <ttmvT-5Qi-3@gated-at.bofh.it> <tttnH-26s-5@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On 04/06/2017 09:04 PM, Michael Ellerman wrote:
> Tyrel Datwyler <tyreld@linux.vnet.ibm.com> writes:
> 
>> On 04/06/2017 03:27 AM, Sachin Sant wrote:
>>> On a POWER8 LPAR running 4.11.0-rc5, a hot unplug operation on
>>> any I/O adapter results in the following warning
>>>
>>> This problem has been in the code for some time now. I had first seen this in
>>> -next tree.
>>>

<snip>

>>> Have attached the dmesg log from the system. Let me know if any additional
>>> information is required to help debug this problem.
>>
>> I remember you mentioning this when the issue was brought up for CPUs. I
>> assume the case is the same here where the issue is only seen with
>> adapters that were hot-added after boot (ie. hot-remove of adapter
>> present at boot doesn't trip the warning)?
> 
> So who's fixing this?

I started looking at it when Bharata submitted a patch trying to fix the
issue for CPUs, but got side tracked by other things. I suspect that
this underflow has actually been an issue for quite some time, and we
are just now becoming aware of it thanks to the recount_t patchset being
merged. I'll look into it again this week.

-Tyrel

> 
> cheers
>

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Re: WARN @lib/refcount.c:128 during hot unplug of I/O adapter. Tyrel Datwyler <tyreld@linux.vnet.ibm.com> - 2017-04-10 20:00 +0200
  Re: WARN @lib/refcount.c:128 during hot unplug of I/O adapter. Michael Ellerman <mpe@ellerman.id.au> - 2017-04-11 11:10 +0200
    Re: WARN @lib/refcount.c:128 during hot unplug of I/O adapter. Tyrel Datwyler <turtle.in.the.kernel@gmail.com> - 2017-04-11 19:20 +0200
      Re: WARN @lib/refcount.c:128 during hot unplug of I/O adapter. Michael Ellerman <mpe@ellerman.id.au> - 2017-04-12 04:20 +0200
        Re: WARN @lib/refcount.c:128 during hot unplug of I/O adapter. Tyrel Datwyler <turtle.in.the.kernel@gmail.com> - 2017-04-12 21:50 +0200

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