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

[Peter Zijlstra]

On Mon, Feb 13, 2023 at 10:25:59AM -0500, Alan Stern wrote:
> On Mon, Feb 13, 2023 at 10:24:13AM +0100, Peter Zijlstra wrote:
> > 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.
> 
> Ah, this is news to me.  Is this sort of thing documented somewhere?

Probably not :/