Re: [PATCH] workaround minor lockdep bug triggered by mm_take_all_locks

[Andrea Arcangeli <andrea@qumranet.com>]

On Tue, Aug 05, 2008 at 05:02:07AM -0700, Roland Dreier wrote:
> check_deadlock operates on classes of locks, so it can warn about
> potential deadlocks, eg if we have
> 
> 	foo(obj1, obj2)
> 	{
> 		lock(obj1);
> 		lock(obj2);
> 		...
> 
> then foo(obj, obj); is a deadlock but lockdep can warn about foo(obj,
> different_obj) without triggering the deadlock in reality.  Of course
> this leads to false positives, and we sometimes have to change correct
> code to help lockdep, but usually such rewriting leads to simpler
> clearer better locking anyway.

It surely doesn't lead to simpler and clearer better locking in the
case we're discussing here, and I don't know of other cases where it
leads to better locking but feel free to make examples.