On Wed, Sep 28, 2016 at 12:53:18AM +1000, Nicholas Piggin wrote: > The more interesting is the ability to avoid the barrier between fastpath > clearing a bit and testing for waiters. > > unlock(): lock() (slowpath): > clear_bit(PG_locked) set_bit(PG_waiter) > test_bit(PG_waiter) test_bit(PG_locked) > > If this was memory ops to different words, it would require smp_mb each > side.. Being the same word, can we avoid them? Ah, that is the reason I put that smp_mb__after_atomic() there. You have a cute point on them being to the same word though. Need to think about that. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>