mutex: Fix/document access-once assumption in mutex_can_spin_on_owner()
mutex: Fix/document access-once assumption in mutex_can_spin_on_owner()

mutex_can_spin_on_owner() is technically broken in that it would
in theory allow the compiler to load lock->owner twice, seeing a
pointer first time and a NULL pointer the second time.

Linus pointed out that a compiler has to be seriously broken to
not compile this correctly - but nevertheless this change
is correct as it will better document the implementation.

Signed-off-by: Peter Zijlstra <3fddac958924aef220f202ca567388ddab3f14a8@infradead.org>
Acked-by: Davidlohr Bueso <d7ca2ed3e31360a26e5e60317ed1b792bd41becb@hp.com>
Acked-by: Waiman Long <a123fdd9fb50e93f03393cfddab9c182b4164439@hp.com>
Acked-by: Linus Torvalds <69652caca27c8b940640ad396ab71f93cacec34f@linux-foundation.org>
Acked-by: Thomas Gleixner <00e4cf8f46a57000a44449bf9dd8cbbcc209fd2a@linutronix.de>
Acked-by: Rik van Riel <a21938f5d463ddf41aa718934c205ca2cce8ebbc@redhat.com>
Cc: Paul E. McKenney <1e0ce936bb9b355d257bf5790d2513c3f28be22b@linux.vnet.ibm.com>
Cc: David Howells <ebac1d06c1688626821bb0e574a037a7a5354e49@redhat.com>
Link: 45c7ca16f927e9ba8647acd7421c445a946ec9e2@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <9dbbbf0688fedc85ad4da37637f1a64b8c718ee2@kernel.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs