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 :/
