On Mon, Feb 15, 2016 at 9:58 AM, Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> wrote: > > Two threads: > > int a, b; > > void thread0(void) > { > WRITE_ONCE(a, 1); > smp_wmb(); > WRITE_ONCE(b, 2); > } > > void thread1(void) > { > WRITE_ONCE(b, 1); > smp_wmb(); > WRITE_ONCE(a, 2); > } > > /* After all threads have completed and the dust has settled... */ > > BUG_ON(a == 1 && b == 1); So the more I look at that kind of litmus test, the less I think that we should care, because I can't come up with a scenario in where that kind of test makes sense. without even a possibility of any causal relationship between the two, I can't say why we'd ever care about the ordering of the (independent) writes to the individual variables. If somebody can make up a causal chain, things differ. But as long as all the CPU's are just doing locally ordered writes, I don't think we need to care about a global store ordering. Linus -- 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