linux-kernel - Re: [PATCH] ipc/msg: Implement lockless pipelined wakeups

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Message-ID: <20151031190633.GA1707@linux-uzut.site>
Date:	Sat, 31 Oct 2015 12:06:33 -0700
From:	Davidlohr Bueso <dave@...olabs.net>
To:	George Spelvin <linux@...izon.com>
Cc:	bigeasy@...utronix.de, tglx@...utronix.de,
	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	manfred@...orfullife.com, peterz@...radead.org
Subject: Re: [PATCH] ipc/msg: Implement lockless pipelined wakeups

On Sat, 31 Oct 2015, Bueso wrote:

>Yes, and this confirms that we still rely on the implicit barrier
>from the cmpxchg as tglx mentioned. As such, we also need to keep
>the pairing when reading 'r_msg' in do_msgrcv(), instead of dropping
>the comments.

Hmm having r_msg as volatile seems even less needed now, we should
drop it. I imagine it was there initially for the busy-wait on the variable
becoming non-nil, but we had cpu_relax _anyway_, so ...
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