Hi, On Sun, Aug 28, 2011 at 12:57 AM, Ming Lei <ming.lei@xxxxxxxxxxxxx> wrote: >> Are you sure? Have you read the documentation about memory barriers to >> confirm this? > > I read the doc again, :-), and it mentions few about mb/wmb/rmb, I think > my above description is still not correct. Generally speaking, mb only > means there is a order between two accesses. > > Now I think only one mb() after 'dummy->hw_token = token;' is enough: > HC will read the up-to-date value of qtd->hw_token after mb() is executed > because of the effect of the mb(), which should be guaranteed by mb. 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. thanks, -- Ming Lei -- 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
