From: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> Date: Tue, 27 May 2008 11:33:46 +1000 > Quick summary: gcc is happily re-ordering readl/writel vs. surrounding > memory accesses (and thus accesses to DMA coherent memory) which is > obviously a _BAD_THING_. > > This is on all archs. Quick fix is to stick a "memory" clobber in all arch > implementations of readl/writel/... (ie, making them a barrier()). > > However, I'm using that as an excuse to bring back my pet subject, which > is basically, should we instead just finally mandate the use of explicit > rmb/wmb/mb's (which boils down to barrier() on x86) to drivers who want > to order memory consistent accesses vs. MMIO ? This is basically what drivers are effectively doing. -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
