On Tue, Jan 06, 2015 at 12:48:42PM +0100, Peter Zijlstra wrote: > > > Looking at that closure stuff, why is there an smp_mb() in > closure_wake_up() ? Typically wakeup only needs to imply a wmb. > > Also note that __closure_wake_up() starts with a fully serializing > instruction (xchg) and thereby already implies the full barrier.
Probably no good reason, that code is pretty old :) If I was to hazard a guess, I had my own lockless linked lists before llist.h existed and perhaps I did it with atomic_xchg() - which was at least documented to not imply a barrier. I suppose it should just be dropped. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
