Re: 2.6.27-rc6: lockdep warning: iprune_mutex at shrink_icache_memory+0x38/0x1a8

Re: 2.6.27-rc6: lockdep warning: iprune_mutex at shrink_icache_memory+0x38/0x1a8

[Dave Chinner]

On Sun, Sep 14, 2008 at 03:31:38AM +0400, Alexander Beregalov wrote:
> Hi
> 
> [ INFO: possible circular locking dependency detected ]
> 2.6.27-rc6-00034-gd1c6d2e #3
> -------------------------------------------------------
> nfsd/1766 is trying to acquire lock:
>  (iprune_mutex){--..}, at: [<c01743fb>] shrink_icache_memory+0x38/0x1a8
> 
>  but task is already holding lock:
>   (&(&ip->i_iolock)->mr_lock){----}, at: [<c021134f>]
>   xfs_ilock+0xa2/0xd6
> 
> 
> I read files through nfs and saw delay for few seconds.
> System is x86_32, nfs, xfs.
> The last working kernel is 2.6.27-rc5,
> I do not know yet is it reproducible or not.

<sigh>

We need a FAQ for this one. It's a false positive.  Google for an
explanation - I've explained it 4 or 5 times in the past year and
asked that the lockdep folk invent a special annotation for the
iprune_mutex (or memory reclaim) because of the way it can cause
recursion into the filesystem and hence invert lock orders without
causing deadlocks.....

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

Re: 2.6.27-rc6: lockdep warning: iprune_mutex at shrink_icache_memory+0x38/0x1a8

[Grant Coady]

On Tue, 16 Sep 2008 12:52:04 +1000, Dave Chinner <david@fromorbit.com> wrote:

>On Sun, Sep 14, 2008 at 03:31:38AM +0400, Alexander Beregalov wrote:
>> Hi
>> 
>> [ INFO: possible circular locking dependency detected ]
>> 2.6.27-rc6-00034-gd1c6d2e #3
>> -------------------------------------------------------
>> nfsd/1766 is trying to acquire lock:
>>  (iprune_mutex){--..}, at: [<c01743fb>] shrink_icache_memory+0x38/0x1a8
>> 
>>  but task is already holding lock:
>>   (&(&ip->i_iolock)->mr_lock){----}, at: [<c021134f>]
>>   xfs_ilock+0xa2/0xd6
>> 
>> 
>> I read files through nfs and saw delay for few seconds.
>> System is x86_32, nfs, xfs.
>> The last working kernel is 2.6.27-rc5,
>> I do not know yet is it reproducible or not.
>
><sigh>
>
>We need a FAQ for this one. It's a false positive.  Google for an
>explanation - I've explained it 4 or 5 times in the past year and
>asked that the lockdep folk invent a special annotation for the
>iprune_mutex (or memory reclaim) because of the way it can cause
>recursion into the filesystem and hence invert lock orders without
>causing deadlocks.....

Yeah, but a 30 second dreadlock?  It's a long wait wondering what's 
gone down or not ;)

Grant.

Re: 2.6.27-rc6: lockdep warning: iprune_mutex at shrink_icache_memory+0x38/0x1a8

[Dave Chinner]

On Tue, Sep 16, 2008 at 02:31:05PM +1000, Grant Coady wrote:
> On Tue, 16 Sep 2008 12:52:04 +1000, Dave Chinner <david@fromorbit.com> wrote:
> 
> >On Sun, Sep 14, 2008 at 03:31:38AM +0400, Alexander Beregalov wrote:
> >> Hi
> >> 
> >> [ INFO: possible circular locking dependency detected ]
> >> 2.6.27-rc6-00034-gd1c6d2e #3
> >> -------------------------------------------------------
> >> nfsd/1766 is trying to acquire lock:
> >>  (iprune_mutex){--..}, at: [<c01743fb>] shrink_icache_memory+0x38/0x1a8
> >> 
> >>  but task is already holding lock:
> >>   (&(&ip->i_iolock)->mr_lock){----}, at: [<c021134f>]
> >>   xfs_ilock+0xa2/0xd6
> >> 
> >> 
> >> I read files through nfs and saw delay for few seconds.
> >> System is x86_32, nfs, xfs.
> >> The last working kernel is 2.6.27-rc5,
> >> I do not know yet is it reproducible or not.
> >
> ><sigh>
> >
> >We need a FAQ for this one. It's a false positive.  Google for an
> >explanation - I've explained it 4 or 5 times in the past year and
> >asked that the lockdep folk invent a special annotation for the
> >iprune_mutex (or memory reclaim) because of the way it can cause
> >recursion into the filesystem and hence invert lock orders without
> >causing deadlocks.....
> 
> Yeah, but a 30 second dreadlock?  It's a long wait wondering what's 
> gone down or not ;)

The delay will be probably due to how slow the system can be when it
runs out of memory, not from the lockdep report.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

Re: 2.6.27-rc6: lockdep warning: iprune_mutex at shrink_icache_memory+0x38/0x1a8

[Alexander Beregalov]

2008/9/16 Dave Chinner <david@fromorbit.com>:
> On Sun, Sep 14, 2008 at 03:31:38AM +0400, Alexander Beregalov wrote:
>> Hi
>>
>> [ INFO: possible circular locking dependency detected ]
>> 2.6.27-rc6-00034-gd1c6d2e #3
>> -------------------------------------------------------
>> nfsd/1766 is trying to acquire lock:
>>  (iprune_mutex){--..}, at: [<c01743fb>] shrink_icache_memory+0x38/0x1a8
>>
>>  but task is already holding lock:
>>   (&(&ip->i_iolock)->mr_lock){----}, at: [<c021134f>]
>>   xfs_ilock+0xa2/0xd6
>>
>>
>> I read files through nfs and saw delay for few seconds.
>> System is x86_32, nfs, xfs.
>> The last working kernel is 2.6.27-rc5,
>> I do not know yet is it reproducible or not.
>
> <sigh>
>
> We need a FAQ for this one. It's a false positive.  Google for an
> explanation - I've explained it 4 or 5 times in the past year and
> asked that the lockdep folk invent a special annotation for the
> iprune_mutex (or memory reclaim) because of the way it can cause
> recursion into the filesystem and hence invert lock orders without
> causing deadlocks.....

Hi Dave

Yes, you already explained a similar message to me, but it was a bug,
not false positive.
http://lkml.org/lkml/2008/7/3/29
http://lkml.org/lkml/2008/7/3/315

I will try to bisect.
It is not a OOM case.

Re: 2.6.27-rc6: lockdep warning: iprune_mutex at shrink_icache_memory+0x38/0x1a8

[Alexander Beregalov]

2008/9/16 Alexander Beregalov <a.beregalov@gmail.com>:
> 2008/9/16 Dave Chinner <david@fromorbit.com>:
>> On Sun, Sep 14, 2008 at 03:31:38AM +0400, Alexander Beregalov wrote:
>>> Hi
>>>
>>> [ INFO: possible circular locking dependency detected ]
>>> 2.6.27-rc6-00034-gd1c6d2e #3
>>> -------------------------------------------------------
>>> nfsd/1766 is trying to acquire lock:
>>>  (iprune_mutex){--..}, at: [<c01743fb>] shrink_icache_memory+0x38/0x1a8
>>>
>>>  but task is already holding lock:
>>>   (&(&ip->i_iolock)->mr_lock){----}, at: [<c021134f>]
>>>   xfs_ilock+0xa2/0xd6
>>>
>>>
>>> I read files through nfs and saw delay for few seconds.
>>> System is x86_32, nfs, xfs.
>>> The last working kernel is 2.6.27-rc5,
>>> I do not know yet is it reproducible or not.
>>
>> <sigh>
>>
>> We need a FAQ for this one. It's a false positive.  Google for an
>> explanation - I've explained it 4 or 5 times in the past year and
>> asked that the lockdep folk invent a special annotation for the
>> iprune_mutex (or memory reclaim) because of the way it can cause
>> recursion into the filesystem and hence invert lock orders without
>> causing deadlocks.....
>
> Hi Dave
>
> Yes, you already explained a similar message to me, but it was a bug,
> not false positive.
> http://lkml.org/lkml/2008/7/3/29
> http://lkml.org/lkml/2008/7/3/315
>
> I will try to bisect.
> It is not a OOM case.
>
I can not reproduce it.