A while back Viro posted a number of 'interesting' mutex_is_locked()
users on IRC, one of those was RCU.
RCU seems to use mutex_is_locked() to avoid doing mutex_trylock(), the
regular load before modify pattern.
While the use isn't wrong per se, its curious in that its needed at all,
mutex_trylock() should be good enough on its own to avoid the pointless
So fix those and remove the mutex_is_locked() (ab)use from RCU.
Reported-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>