On Sun, 28 Aug 2011, Ming Lei wrote: > Looks like there is still another similar problem in qh_link_async(): > the last wmb > should be changed into mb, because HC will read 'head->hw->hw_next' from qh > descriptor and this pointer in qh is read only for HC. But this problem can't be > observed on ARM, since wmb on ARM is same with mb. It doesn't matter what the HC does -- the wmb() instruction is executed by the CPU, not the HC. The point of that instruction is to make sure that the qh->hw->hw_next = head->hw->hw_next; line (and all the preceding lines as well) is ordered before the head->hw->hw_next = dma; 3C line. Since both of these lines are writes, not reads, it suffices to use wmb() rather than mb(). Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
