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Date: Thu, 26 Mar 2015 19:54:20 +0100
From: Christian Borntraeger <borntraeger@de.ibm.com>
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To: Linus Torvalds <torvalds@linux-foundation.org>
CC: Peter Zijlstra <peterz@infradead.org>, Will Deacon <will.deacon@arm.com>,
        Stephen Rothwell <sfr@canb.auug.org.au>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>,
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        Davidlohr Bueso <dave@stgolabs.net>,
        Paul McKenney <paulmck@linux.vnet.ibm.com>
Subject: Re: linux-next: build warnings after merge of the access_once tree
References: <20150326193112.2c87eb39@canb.auug.org.au> <20150326103442.GV21418@twins.programming.kicks-ass.net> <20150326132750.GA2805@arm.com> <20150326142220.GY21418@twins.programming.kicks-ass.net> <CA+55aFyLTc72-xTkjugVSMb3EQq=+__UcFe28agu086xf9d6ZA@mail.gmail.com> <551440C5.8040104@de.ibm.com> <CA+55aFw6f4sLc4DMTmd2T9-r8NNQq8Zr4Wf1SvHSG=s1Vd-WuA@mail.gmail.com>
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Am 26.03.2015 um 18:52 schrieb Linus Torvalds:
> On Thu, Mar 26, 2015 at 10:24 AM, Christian Borntraeger
> <borntraeger@de.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