linux-kernel - Re: linux-next: build warnings after merge of the access

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Message-ID: <20150326164441.GH24151@twins.programming.kicks-ass.net>
Date:	Thu, 26 Mar 2015 17:44:42 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Will Deacon <will.deacon@....com>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Christian Borntraeger <borntraeger@...ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	"linux-next@...r.kernel.org" <linux-next@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Davidlohr Bueso <dave@...olabs.net>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>
Subject: Re: linux-next: build warnings after merge of the access_once tree

On Thu, Mar 26, 2015 at 05:36:47PM +0100, Peter Zijlstra wrote:
> Can't we make an argument that these barrier calls are not required? The
> memcpy() call already guarantees we emit the loads and its opaque so the
> compiler cannot 'cache' the value. So I see not immediate reason for the
> dual memory clobber.

Oh wait, it needs to reassess the content of the target variable after
the memcpy of course.

Could we then at least make the 64bit case unconditional as well?

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