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Date:   Thu, 17 Jan 2019 09:13:14 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     Johannes Weiner <hannes@cmpxchg.org>
Cc:     Suren Baghdasaryan <surenb@google.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Tejun Heo <tj@kernel.org>, lizefan@huawei.com, axboe@kernel.dk,
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        Ingo Molnar <mingo@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
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        linux-mm <linux-mm@kvack.org>, linux-doc@vger.kernel.org,
        LKML <linux-kernel@vger.kernel.org>, kernel-team@android.com
Subject: Re: [PATCH v2 5/5] psi: introduce psi monitor
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On Wed, Jan 16, 2019 at 02:17:28PM -0500, Johannes Weiner wrote:

> > > Also, you probably want to use atomic_t for g->polling, because we
> > > (sadly) have architectures where regular stores and atomic ops don't
> > > work 'right'.
> > 
> > Oh, I see. Will do. Thanks!
> 
> Yikes, that's news to me too. Good to know.

See Documentation/atomic_t.txt, specifically the atomic_set() part in
SEMANTICS.

Archs that suffer this include (but are not limited to): parisc,
sparc32-smp, something arc.

And yes, I would dearly love to kill all SMP support for architectures
like that..