Re: [PATCH RFC] drivers/core: Replace lockdep_set_novalidate_class() with unique class keys

[Peter Zijlstra]

On Sun, Feb 12, 2023 at 10:23:44AM -0500, Alan Stern wrote:
> Provided it acquires the parent device's lock first, this is 
> utterly safe no matter what order the children are locked in.  Try 
> telling that to lockdep! 

mutex_lock_next_lock(child->lock, parent->lock) is there to express this
exact pattern, it allows taking multiple child->lock class locks (in any
order) provided parent->lock is held.