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Date: Wed, 11 Oct 2017 10:34:23 -0700 From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> To: Peter Zijlstra <peterz@...radead.org> Cc: David Howells <dhowells@...hat.com>, Will Deacon <will.deacon@....com>, linux-kernel@...r.kernel.org, mingo@...nel.org, torvalds@...ux-foundation.org, mark.rutland@....com, linux-arch@...r.kernel.org, Jonathan Corbet <corbet@....net>, Alexander Kuleshov <kuleshovmail@...il.com>, dvyukov@...gle.com Subject: Re: [PATCH RFC tip/core/rcu 12/15] lib/assoc_array: Remove smp_read_barrier_depends() On Wed, Oct 11, 2017 at 07:11:37PM +0200, Peter Zijlstra wrote: > On Wed, Oct 11, 2017 at 10:06:31AM -0700, Paul E. McKenney wrote: > > > This, you mean? > > > > data = rcu_dereference_sched(*this_cpu_ptr(&cpufreq_update_util_data)); > > Yep, that one. Although in my tree it now appears to look like: > > data = rcu_dereference_sched(*per_cpu_ptr(&cpufreq_update_util_data, > cpu_of(rq))); So in the non-RCU case, we could simply replace rcu_dereference_sched() with ACCESS_ONCE(), right? Thus no need to change the per-CPU primitives. Especially given that most uses of per-CPU variables don't even need protection from load/store tearing, let alone protection from Alpha. Or am I missing something subtle here? Thanx, Paul
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