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

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Message-ID: <5638C180.6050901@linutronix.de>
Date:	Tue, 3 Nov 2015 15:15:28 +0100
From:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:	Davidlohr Bueso <dave@...olabs.net>,
	George Spelvin <linux@...izon.com>
Cc:	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 10/31/2015 08:06 PM, Davidlohr Bueso wrote:
> 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 ...

Didn't noticed that. So that volatile part and the casts are gone, too.

Sebastian
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