On Wed, Oct 11, 2017 at 05:07:05PM +0100, David Howells wrote: > Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> wrote: > > > It does not. In most cases, the barriered version would be > > smp_store_release(). > > Ummm... Is that good enough? Is: > > WRITE_ONCE(x, 1); > WRITE_ONCE(x, 2); > > equivalent to: > > smp_store_release(x, 1); > smp_store_release(x, 2); > > if CONFIG_SMP=n? Almost; it ends up being: barrier(); WRITE_ONCE(x, 1); barrier(); WRITE_ONCE(x, 2); > (Consider what happens if an interrupt messes with x). > > If it is good enough, should we be using smp_load_acquire() rather than > READ_ONCE()? No, smp_load_acquire() is strictly stronger (and far more expensive on !Alpha). Dependent loads do not require barriers (except Alpha, and we want to kill that special case).
