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From: David Howells <dhowells@redhat.com>
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To: Peter Zijlstra <peterz@infradead.org>
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        Michal Hocko <mhocko@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
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Subject: Re: [RFC 10/12] x86, rwsem: simplify __down_write
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Date: Thu, 09 Jun 2016 15:40:58 +0100
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Peter Zijlstra <peterz@infradead.org> wrote:

> Blergh; so looking at more asm there's still a few tricks we cannot do.
> So while overall size is down, some paths do end up more expensive. (It
> typically boils down to creative use of condition flags, which is very
> hard in C)

It can be done using ISO __atomic_fetch_add() and suchlike.

David