Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> wrote: > - node = result.terminal_node.node; > - smp_read_barrier_depends(); > + node = READ_ONCE(result.terminal_node.node); /* Address dependency. */ The main problem I have with this method of annotation is that it's not obvious there's a barrier there or which side the barrier is. I think one of the trickiest issues is that a barrier is typically between two things and we're not making it clear what those two things actually are. Also, I would say that the most natural interpretation of READ_ONCE() is that the implicit barrier comes after the read, e.g.: f = READ_ONCE(stuff->foo); /* Implied barrier */ look_at(f->a); look_at(f->b); I.e. READ_ONCE() prevents stuff->foo from being reread whilst you access f and orders LOAD(stuff->foo) before LOAD(f->a) and LOAD(f->b). David
