* Using nested locking for spin_lock_bh
@ 2012-03-28 16:36 Sven Eckelmann
2012-03-29 3:11 ` Yong Zhang
2012-04-15 11:18 ` Peter Zijlstra
0 siblings, 2 replies; 4+ messages in thread
From: Sven Eckelmann @ 2012-03-28 16:36 UTC (permalink / raw)
To: Peter Zijlstra, Ingo Molnar, linux-kernel; +Cc: simon.wunderlich, Marek Lindner
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Hi,
I started to run some experimental batman-adv code inside some virtual
machines with different debugging functions enabled. One of them was lockdep.
There we noticed a false positive for a lock class that is actually used in
two different data structures. Therefore, lockdep noticed that there could be
a deadlock for this class in a function that locks the two different data
structures.
To resolve this problem, I wanted to define two different subclasses and
replace the spin_lock_bh with its nested version. The only problem now is the
absence of spin_lock_bh_nested. I could only find spin_lock_bh and
spin_lock_irqsave_nested.
Is there another way how this should be done or is there a general problem why
there is no nested support for this incarnation of spin_lock?
Kind regards,
Sven
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^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: Using nested locking for spin_lock_bh
2012-03-28 16:36 Using nested locking for spin_lock_bh Sven Eckelmann
@ 2012-03-29 3:11 ` Yong Zhang
2012-03-29 10:41 ` Sven Eckelmann
2012-04-15 11:18 ` Peter Zijlstra
1 sibling, 1 reply; 4+ messages in thread
From: Yong Zhang @ 2012-03-29 3:11 UTC (permalink / raw)
To: Sven Eckelmann
Cc: Peter Zijlstra, Ingo Molnar, linux-kernel, simon.wunderlich,
Marek Lindner
On Wed, Mar 28, 2012 at 06:36:39PM +0200, Sven Eckelmann wrote:
> Hi,
>
> I started to run some experimental batman-adv code inside some virtual
> machines with different debugging functions enabled. One of them was lockdep.
> There we noticed a false positive for a lock class that is actually used in
> two different data structures.
Hmm, I think you can initialize the lock class in the two differnent data
structures with differnt lock_class_key.
Thanks,
Yong
> Therefore, lockdep noticed that there could be
> a deadlock for this class in a function that locks the two different data
> structures.
>
> To resolve this problem, I wanted to define two different subclasses and
> replace the spin_lock_bh with its nested version. The only problem now is the
> absence of spin_lock_bh_nested. I could only find spin_lock_bh and
> spin_lock_irqsave_nested.
>
> Is there another way how this should be done or is there a general problem why
> there is no nested support for this incarnation of spin_lock?
>
> Kind regards,
> Sven
--
Only stand for myself
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: Using nested locking for spin_lock_bh
2012-03-29 3:11 ` Yong Zhang
@ 2012-03-29 10:41 ` Sven Eckelmann
0 siblings, 0 replies; 4+ messages in thread
From: Sven Eckelmann @ 2012-03-29 10:41 UTC (permalink / raw)
To: Yong Zhang
Cc: Peter Zijlstra, Ingo Molnar, linux-kernel, simon.wunderlich,
Marek Lindner
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On Thursday, March 29, 2012 11:11:37 AM Yong Zhang wrote:
> On Wed, Mar 28, 2012 at 06:36:39PM +0200, Sven Eckelmann wrote:
> > Hi,
> >
> > I started to run some experimental batman-adv code inside some virtual
> > machines with different debugging functions enabled. One of them was
> > lockdep. There we noticed a false positive for a lock class that is
> > actually used in two different data structures.
>
> Hmm, I think you can initialize the lock class in the two differnent data
> structures with differnt lock_class_key.
Thanks. I think I understand the problem now a little bit better and could
resolve it using lockdep_set_class.
Kind regards,
Sven
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^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: Using nested locking for spin_lock_bh
2012-03-28 16:36 Using nested locking for spin_lock_bh Sven Eckelmann
2012-03-29 3:11 ` Yong Zhang
@ 2012-04-15 11:18 ` Peter Zijlstra
1 sibling, 0 replies; 4+ messages in thread
From: Peter Zijlstra @ 2012-04-15 11:18 UTC (permalink / raw)
To: Sven Eckelmann; +Cc: Ingo Molnar, linux-kernel, simon.wunderlich, Marek Lindner
On Wed, 2012-03-28 at 18:36 +0200, Sven Eckelmann wrote:
>
> Is there another way how this should be done or is there a general problem why
> there is no nested support for this incarnation of spin_lock?
No reason other than that it wasn't needed before now, but I see you've
resolved things with a lockdep_set_class() which works too.
^ permalink raw reply [flat|nested] 4+ messages in thread
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2012-03-28 16:36 Using nested locking for spin_lock_bh Sven Eckelmann
2012-03-29 3:11 ` Yong Zhang
2012-03-29 10:41 ` Sven Eckelmann
2012-04-15 11:18 ` Peter Zijlstra
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