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

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Message-ID: <551455DC.4080604@de.ibm.com>
Date:	Thu, 26 Mar 2015 19:54:20 +0100
From:	Christian Borntraeger <borntraeger@...ibm.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Peter Zijlstra <peterz@...radead.org>,
	Will Deacon <will.deacon@....com>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	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

Am 26.03.2015 um 18:52 schrieb Linus Torvalds:
> On Thu, Mar 26, 2015 at 10:24 AM, Christian Borntraeger
> <borntraeger@...ibm.com> wrote:
>>
>> Oh I just added that check back then because some guy named
>> Linus suggested something like that ;-)
> 
> Yes, my bad.
> 
> In my defense, that was when we were talking about ACCESS_ONCE()
> causing bugs with gcc due to the blind use of "volatile" that it turns
> out gcc doesn't necessarily like.
> 
> With the memcpy fallback (and the simpler "scalar pointer copy by
> hand"), I think READ_ONCE() (and WRITE_ONCE()) are safe.
> 
>                       Linus
> 

FWIW, I dropped the warning fixp patch from my linux-next branch so
everything should be back to normal and we can merge Peters patch for 4.0 or
4.1.

Christian

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