Messages in this thread | | | Date | Tue, 5 Dec 2017 20:17:33 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH tip/core/rcu 21/21] drivers/vhost: Remove now-redundant read_barrier_depends() |
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On Tue, Dec 05, 2017 at 08:57:46PM +0200, Michael S. Tsirkin wrote:
> I don't see WRITE_ONCE inserting any barriers, release or > write.
Correct, never claimed there was.
Just saying that:
obj = READ_ONCE(*foo); val = READ_ONCE(obj->val);
Never needs a barrier (except on Alpha and we want to make that go away). Simply because a CPU needs to complete the load of @obj before it can compute the address &obj->val. Thus the second load _must_ come after the first load and we get LOAD-LOAD ordering.
Alpha messing that up is a royal pain, and Alpha not being an active/living architecture is just not worth the pain of keeping this in the generic model.
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