linux-kernel - Re: compiler bug gcc4.6/4.7 with ACCESS

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Message-ID: <CA+55aFw+cLJ6xW0Wk6nMbK+e1yr2KGCWN+-v2a7xK1u8zTtDtA@mail.gmail.com>
Date:	Tue, 11 Nov 2014 16:36:06 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Christian Borntraeger <borntraeger@...ibm.com>
Cc:	Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...nel.org>,
	Paolo Bonzini <pbonzini@...hat.com>, KVM <kvm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Andreas Krebbel <Andreas.Krebbel@...ibm.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Cornelia Huck <cornelia.huck@...ibm.com>,
	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>
Subject: Re: compiler bug gcc4.6/4.7 with ACCESS_ONCE and workarounds

On Tue, Nov 11, 2014 at 4:33 PM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> I guess as a workaround it is fine, as long as we don't lose sight of
> trying to eventually do a better job.

Oh, and when it comes to the actual gcc bug - do you have any reason
to believe that it's somehow triggered more easily by something
particular in the arch/s390/kvm/gaccess.c code?

IOW, why does this problem not hit the x86 spinlocks that also use
volatile pointers to aggregate types? Or does it?

                       Linus
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