Bug 17752

bugzilla-daemon@bugzilla.kernel.org wrote:
> https://bugzilla.kernel.org/show_bug.cgi?id=17752
> 
> 
> Maciej Rutecki <maciej.rutecki@gmail.com> changed:
> 
>            What    |Removed                     |Added
> ----------------------------------------------------------------------------
>              Blocks|                            |16444

This is probably not a regression.  See this earlier discussion:
http://lkml.org/lkml/2010/1/15/76

And another report, coincidentally at the same time:
http://lkml.org/lkml/2010/1/18/108

As I understand Christoph's post on January 19, several code paths are
independently affected:
http://lkml.org/lkml/2010/1/19/267
(Maybe some of those have been fixed in the meantime.)

I don't see in my trace from September 1 which filesystem caused the
particular lockdep report.  I may have unmounted ext4, vfat, or fuse prior to
that.

Dave wrote on September 2:
>> Any memory allocation that enters reclaim in the unmount path will
>> generate this warning. The problem is that the normal memory reclaim
>> path is:
>> 
>>      alloc -> reclaim -> shrink_slab -> shrink_icache_memory -> iprune_sem
>> -> s_umount
>> 
>> while unmmount does:
>> 
>>      unmount -> s_umount -> alloc -> lockdep goes boom!
>> or
>>      unmount -> iprune_sem -> alloc -> lockdep goes boom!
>> 
>> I never got a straight answer on this, but it the warnings are
>> indicating that you must use GFP_NOFS allocations for every
>> allocation in the unmount path, which is kind of hard to know
>> about given the code is not unomunt path specific....

Is it feasible to add a gfp_flag argument to all call chains that could lead
to allocations in unmount?

On Monday, September 20, 2010, Stefan Richter wrote:
> Rafael J. Wysocki wrote:
> > This message has been generated automatically as a part of a summary report
> > of recent regressions.
> > 
> > The following bug entry is on the current list of known regressions
> > from 2.6.35.  Please verify if it still should be listed and let the
> tracking team
> > know (either way).
> > 
> > 
> > Bug-Entry   : http://bugzilla.kernel.org/show_bug.cgi?id=17752
> > Subject             : 2.6.36-rc3: inconsistent lock state (iprune_sem,
> shrink_icache_memory)
> > Submitter   : Stefan Richter <stefanr@s5r6.in-berlin.de>
> > Date                : 2010-09-01 6:37 (20 days old)
> > Message-ID  : <tkrat.ed8eda6bc8ffe64e@s5r6.in-berlin.de>
> > References  : http://marc.info/?l=linux-kernel&m=128332308528119&w=2
> 
> I think this should not be marked as a regression.  See the older reports of
> very similar issues (in my LKML mail from September 3, logged in bugzilla in
> comment #1)
>       http://lkml.org/lkml/2010/1/15/76       (2.6.33-rc, xfs involved)
>       http://lkml.org/lkml/2010/1/18/108      (2.6.32.y, ntfs involved)
> and hch's analysis in the first of these two threads
>       http://lkml.org/lkml/2010/1/19/267      (several filesystems and
>                                                other code paths)
> So, unless my trace was a code path that only newly acquired that oldproblem
> of other code paths, this is an older issue.  Alas this is not obvious to me
> at least from the log that I got.
> 
> I did not have lockdep enabled on the machine which delivered the log during
> the last few months or so; I just remembered to re-enable it at the occasion
> of switching to 2.6.36-rc.

Dropping from the list of recent regressions.