Messages in this thread | | | Date | Mon, 2 Nov 2015 17:25:32 -0800 | Subject | Re: [PATCH 4/4] locking: Introduce smp_cond_acquire() | From | Linus Torvalds <> |
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On Mon, Nov 2, 2015 at 5:14 PM, Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote: > > You would ask that question when I am many thousands of miles from my > copy of the Alpha reference manual! ;-)
I don't think I've touched a paper manual in years. Too m uch effort to index and search. Look here
http://download.majix.org/dec/alpha_arch_ref.pdf
> There is explicit wording in that manual that says that no multi-variable > ordering is implied without explicit memory-barrier instructions.
Right. But the whole "read -> conditional -> write" ends up being a dependency chain to *every* single write that happens after the conditional.
So there may be no "multi-variable ordering" implied in any individual access, but despite that a simple "read + conditional" orders every single store that comes after it. Even if it orders them "individually".
Linus
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