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Date: Mon, 2 Nov 2015 17:25:32 -0800 From: Linus Torvalds <torvalds@...ux-foundation.org> To: Paul McKenney <paulmck@...ux.vnet.ibm.com> Cc: Will Deacon <will.deacon@....com>, Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...nel.org>, Oleg Nesterov <oleg@...hat.com>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, boqun.feng@...il.com, Jonathan Corbet <corbet@....net>, Michal Hocko <mhocko@...nel.org>, David Howells <dhowells@...hat.com> Subject: Re: [PATCH 4/4] locking: Introduce smp_cond_acquire() On Mon, Nov 2, 2015 at 5:14 PM, Paul E. McKenney <paulmck@...ux.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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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