linux-kernel - Re: [PATCH RT] seqlock: provide the same ordering semantics as mainline

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Date:   Mon, 28 May 2018 17:30:32 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Julia Cartwright <julia@...com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Al Viro <viro@...iv.linux.org.uk>,
        John Ogness <john.ogness@...utronix.de>,
        Will Deacon <will.deacon@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Gratian Crisan <gratian.crisan@...com>,
        linux-rt-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        stable-rt@...r.kernel.org
Subject: Re: [PATCH RT] seqlock: provide the same ordering semantics as
 mainline

On 2018-04-26 15:02:03 [-0500], Julia Cartwright wrote:
> The mainline implementation of read_seqbegin() orders prior loads w.r.t.
> the read-side critical section.  Fixup the RT writer-boosting
> implementation to provide the same guarantee.
> 
> Also, while we're here, update the usage of ACCESS_ONCE() to use
> READ_ONCE().

I'm taking this without the READ_ONCE hunk because ACCESS_ONCE is gone
since v4.15 and I had to move on in v4.16.

> Fixes: e69f15cf77c23 ("seqlock: Prevent rt starvation")
> Cc: stable-rt@...r.kernel.org
> Signed-off-by: Julia Cartwright <julia@...com>

Sebastian