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Message-ID: <20160115212714.GM3421@worktop>
Date: Fri, 15 Jan 2016 22:27:14 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc: Leonid Yegoshin <Leonid.Yegoshin@...tec.com>,
Will Deacon <will.deacon@....com>,
"Michael S. Tsirkin" <mst@...hat.com>,
linux-kernel@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
linux-arch@...r.kernel.org,
Andrew Cooper <andrew.cooper3@...rix.com>,
Russell King - ARM Linux <linux@....linux.org.uk>,
virtualization@...ts.linux-foundation.org,
Stefano Stabellini <stefano.stabellini@...citrix.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
Joe Perches <joe@...ches.com>,
David Miller <davem@...emloft.net>, linux-ia64@...r.kernel.org,
linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
sparclinux@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linux-metag@...r.kernel.org, linux-mips@...ux-mips.org,
x86@...nel.org, user-mode-linux-devel@...ts.sourceforge.net,
adi-buildroot-devel@...ts.sourceforge.net,
linux-sh@...r.kernel.org, linux-xtensa@...ux-xtensa.org,
xen-devel@...ts.xenproject.org, Ralf Baechle <ralf@...ux-mips.org>,
Ingo Molnar <mingo@...nel.org>, ddaney.cavm@...il.com,
james.hogan@...tec.com, Michael Ellerman <mpe@...erman.id.au>
Subject: Re: [v3,11/41] mips: reuse asm-generic/barrier.h
On Fri, Jan 15, 2016 at 09:46:12AM -0800, Paul E. McKenney wrote:
> On Fri, Jan 15, 2016 at 10:13:48AM +0100, Peter Zijlstra wrote:
> > And the stuff we're confused about is how best to express the difference
> > and guarantees of these two forms of transitivity and how exactly they
> > interact.
>
> Hoping my memory-barrier.txt patch helps here...
Yes, that seems a good start. But yesterday you raised the 'fun' point
of two globally ordered sequences connected by a single local link.
And I think I'm still confused on LWSYNC (in the smp_wmb case) when one
of the stores looses a conflict, and if that scenario matters. If it
does, we should inspect the same case for other barriers.
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