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: <20130605050719.GC10475@kroah.com>
Date:	Tue, 4 Jun 2013 22:07:19 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Joe Lawrence <joe.lawrence@...atus.com>
Cc:	Rusty Russell <rusty@...tcorp.com.au>,
	Ben Greear <greearb@...delatech.com>,
	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 Mon, Jun 03, 2013 at 10:17:17AM -0400, Joe Lawrence wrote:
> [Cc: stable@...r.kernel.org]
> 
> Third time is a charm?  The stable address was incorrect from the first 
> msg in this thread, but the relevant bits remain quoted below...

Really?  I'm totally confused...

> On Mon, 3 Jun 2013, Joe Lawrence wrote:
> 
> > [fixing Cc: stable@...nel.org address]
> > 
> > On Sun, 2 Jun 2013, Joe Lawrence wrote:
> > 
> > > On Sun, 2 Jun 2013, Rusty Russell wrote:
> > > 
> > > > Ben Greear <greearb@...delatech.com> writes:
> > > > 
> > > > > It turns out, the bug I spent yesterday chasing in various 3.9 kernels is apparently
> > > > > fixed by the commit in the title (c9c390bb5535380d40614571894ef0c00bc026ff).
> > > > 
> > > > Apparently being the operative word.
> > > > 
> > > > This commit avoids the entire "module insert failed due to sysfs race"
> > > > path in the common case, it doesn't fix any actual problem.
> > > > 
> > > > I think the real commit you want is Linus' kobject fix
> > > > a49b7e82cab0f9b41f483359be83f44fbb6b4979 "kobject: fix kset_find_obj()
> > > > race with concurrent last kobject_put()".
> > > > 
> > > > Or is that already in stable?
> > > 
> > > 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.
> > > 
> > > Hope this clarifies things.

After this whole thread, what should I be doing for the 3.9-stable tree?
Add commit 944a1fa?  Or something else?

confused,

greg k-h
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