linux-kernel - Re: Please add to stable: module: don't unlink the module until we've removed all exposure.

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Message-ID: <51ACC60B.8090504@candelatech.com>
Date:	Mon, 03 Jun 2013 09:36:27 -0700
From:	Ben Greear <greearb@...delatech.com>
To:	Joe Lawrence <joe.lawrence@...atus.com>
CC:	Rusty Russell <rusty@...tcorp.com.au>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	stable@...r.kernel.org
Subject: Re: Please add to stable:  module: don't unlink the module until
 we've removed all exposure.

On 06/03/2013 08:59 AM, Ben Greear wrote:
> On 06/03/2013 07:17 AM, Joe Lawrence wrote:
>
>>>> Hi Rusty,
>>>>
>>>> I had pointed Ben (offlist) to that bugzilla entry without realizing
>>>> there were other earlier related fixes in this space.  Re-viewing bz-
>>>> 58011, it looks like it was opened against 3.8.12, while Ben and myself
>>>> had encountered module loading problems in versions 3.9 and
>>>> 3.9.[1-3].  I can update the bugzilla entry to add a comment noting commit
>>>> a49b7e82 "kobject: fix kset_find_obj() race with concurrent last
>>>> kobject_put()".
>>>>
>>>> That said, it doesn't appear that commit 944a1fa "module: don't unlink the
>>>> module until we've removed all exposure" has not made it into any stable
>>>> kernel.  On my system, applying this on top of 3.9 resolved a module
>>>> unload/load race that would occasionally occur on boot (two video adapters
>>>> of the same make, the module unloads for whatever reason and I see "module
>>>> is already loaded" and "sysfs: cannot create duplicate filename
>>>> '/module/mgag200'" messages every 5-10% instances.)  I have logs if you
>>>> were interested in these warnings/crashes.
>
> It at least works around the problem for me as well.  But, a more rare
> migration/[0-3] (I think) related lockup still exists in 3.9.4 for me,
> so I will also try applying that other kobject patch and continue testing
> today...

Well, that other kobject patch is already in 3.9.4, so I think it's still
a good idea to include the
"module: don't unlink the module until we've removed all exposure."
patch in stable.  I have a decent test case to reproduce the crash, so if someone
wants me to test other patches instead, then I will do so.

Thanks,
Ben

-- 
Ben Greear <greearb@...delatech.com>
Candela Technologies Inc  http://www.candelatech.com

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