On Mon, Nov 20, 2017 at 08:28:06PM +0100, Peter Zijlstra wrote: > On Mon, Nov 20, 2017 at 06:05:55PM +0000, Will Deacon wrote: > > This is a thorny issue, but RCU (specifically rcu_dereference but probably > > also some READ_ONCEs) relies on being able to utilise syntactic dependency > > chains to order local accesses to shared variables. > > Well, we used to have READ_ONCE() and smp_read_barrier_depends(), but > we recently munged them together, in the process getting rid of > lockless_dereference(). > > So for sure, READ_ONCE() must be able to do the address dependency > thing, otherwise tons of code comes apart. I do hope that they track the volatile accesses produced by READ_ONCE(). Otherwise, it would not be good to apply this to anything touching MMIO. Thanx, Paul -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
