Re: Using nested locking for spin_lock_bh

[Yong Zhang]

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



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