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Date:   Tue, 19 Jun 2018 16:30:44 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Quentin Perret <quentin.perret@arm.com>
Cc:     rjw@rjwysocki.net, gregkh@linuxfoundation.org,
        linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
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        edubezval@gmail.com, srinivas.pandruvada@linux.intel.com,
        currojerez@riseup.net, javi.merino@kernel.org
Subject: Re: [RFC PATCH v3 03/10] PM: Introduce an Energy Model management
 framework
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On Tue, Jun 19, 2018 at 04:21:16PM +0200, Peter Zijlstra wrote:
> On Tue, Jun 19, 2018 at 04:16:42PM +0200, Peter Zijlstra wrote:
> > On Tue, Jun 19, 2018 at 02:38:45PM +0100, Quentin Perret wrote:
> > > But maybe I could use something simpler than a lock in this case ?
> > > Would WRITE_ONCE/READ_ONCE be enough to ensure that atomicity for
> > > example ?
> > 
> > Yes, since its a single pointer, smp_store_release() + READ_ONCE()
> > should be sufficient (these are the foundations of RCU).
> 
> Note that per_cpu()/this_cpu_read() and friends should imply READ_ONCE().

Mark reminded me that per_cpu() does not in fact imply that, but
READ_ONCE(per_cpu()) should work.