On Tue, 2018-03-27 at 11:44 +0200, Arnd Bergmann wrote: > > The interesting thing is that we do seem to have a whole LOT of these > > spurrious wmb before writel all over the tree, I suspect because of > > that incorrect recommendation in memory-barriers.txt. > > > > We should fix that. > > Maybe the problem is just that it's so counter-intuitive that we don't > need that barrier in Linux, when the hardware does need one on some > architectures. > > How about we define a barrier type instruction specifically for this > purpose, something like wmb_before_mmio() and have all architectures > define that to an empty macro? This is exactly what wmb() is about and exactly what Linux rejected back in the day (and in hindsight I agree with him). > That way, having correct code using wmb_before_mmio() will not > trigger an incorrect review comment that leads to extra wmb(). ;-) Ah, you mean have an empty macro that will always be empty on all architectures just to fool people ? :-) Not sure that will fly ... I think we just need to be documenting that stuff better and not have incorrect examples. Also a sweep to remove some useless ones like the one in e1000e would help. Cheers, Ben. -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
