On 10/04, Peter Zijlstra wrote: > > On Fri, Oct 04, 2013 at 05:13:23PM +0200, Oleg Nesterov wrote: > > > I am not trying saying this feature is "must have", of course it > > is not. The only problem, I am a bit puzzled why you dislike it > > that much. > > The reason I dislike it is because I feel we're now mixing two objects > into one; one object doing mutual exclusion and one object being > terribly smart with sync_rcu.
OK, I see your point. But rcu_sync_struct has to serialize the writers anyway. The only question is how many other writers the thread doing ->sync() should wakeup and when. And otoh. Currently nobody needs the non-exclusive mode (cpu-hotplug doesn't care because it is always exclusive itself). And in fact you initially argued with wake_up_all ;) "exclusive" is more natural, it is like rw_semaphore. However, yes-yes-yes, I do think that we need the non-exclusive mode too, at least for percpu_down_write_nonexclusive() which I think we need as well. Oleg. -- 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/
