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Re: [Xen-devel] [v3,11/41] mips: reuse asm-generic/barrier.h
- To: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
- From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
- Date: Tue, 26 Jan 2016 11:19:27 +0100
- Cc: linux-mips@xxxxxxxxxxxxxx, linux-ia64@xxxxxxxxxxxxxxx, "Michael S. Tsirkin" <mst@xxxxxxxxxx>, Will Deacon <will.deacon@xxxxxxx>, virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx, "H. Peter Anvin" <hpa@xxxxxxxxx>, sparclinux@xxxxxxxxxxxxxxx, Ingo Molnar <mingo@xxxxxxxxxx>, linux-arch@xxxxxxxxxxxxxxx, linux-s390@xxxxxxxxxxxxxxx, Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx>, user-mode-linux-devel@xxxxxxxxxxxxxxxxxxxxx, linux-sh@xxxxxxxxxxxxxxx, Michael Ellerman <mpe@xxxxxxxxxxxxxx>, x86@xxxxxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxxx, Ingo Molnar <mingo@xxxxxxx>, linux-xtensa@xxxxxxxxxxxxxxxx, james.hogan@xxxxxxxxxx, Arnd Bergmann <arnd@xxxxxxxx>, Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>, adi-buildroot-devel@xxxxxxxxxxxxxxxxxxxxx, Leonid Yegoshin <Leonid.Yegoshin@xxxxxxxxxx>, ddaney.cavm@xxxxxxxxx, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, linux-metag@xxxxxxxxxxxxxxx, linux-arm-kernel@xxxxxxxxxxxxxxxxxxx, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, Ralf Baechle <ralf@xxxxxxxxxxxxxx>, Joe Perches <joe@xxxxxxxxxxx>, linuxppc-dev@xxxxxxxxxxxxxxxx, David Miller <davem@xxxxxxxxxxxxx>
- Delivery-date: Tue, 26 Jan 2016 10:19:52 +0000
- List-id: Xen developer discussion <xen-devel.lists.xen.org>
On Mon, Jan 25, 2016 at 10:03:22PM -0800, Paul E. McKenney wrote:
> On Mon, Jan 25, 2016 at 04:42:43PM +0000, Will Deacon wrote:
> > On Fri, Jan 15, 2016 at 01:58:53PM -0800, Paul E. McKenney wrote:
> > > On Fri, Jan 15, 2016 at 10:27:14PM +0100, Peter Zijlstra wrote:
> > > > Yes, that seems a good start. But yesterday you raised the 'fun' point
> > > > of two globally ordered sequences connected by a single local link.
> > >
> > > The conclusion that I am slowly coming to is that litmus tests should
> > > not be thought of as linear chains, but rather as cycles. If you think
> > > of it as a cycle, then it doesn't matter where the local link is, just
> > > how many of them and how they are connected.
> >
> > Do you have some examples of this? I'm struggling to make it work in my
> > mind, or are you talking specifically in the context of the kernel
> > memory model?
>
> Now that you mention it, maybe it would be best to keep the transitive
> and non-transitive separate for the time being anyway. Just because it
> might be possible to deal with does not necessarily mean that we should
> be encouraging it. ;-)
So isn't smp_mb__after_unlock_lock() exactly such a scenario? And would
not someone trying to implement RCsc locks using locally transitive
RELEASE/ACQUIRE operations need exactly this stuff?
That is, I am afraid we need to cover the mix of local and global
transitive operations at least in overview.
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- References:
- Re: [Xen-devel] [v3,11/41] mips: reuse asm-generic/barrier.h
- Re: [Xen-devel] [v3,11/41] mips: reuse asm-generic/barrier.h
- Re: [Xen-devel] [v3,11/41] mips: reuse asm-generic/barrier.h
- Re: [Xen-devel] [v3,11/41] mips: reuse asm-generic/barrier.h
- Re: [Xen-devel] [v3,11/41] mips: reuse asm-generic/barrier.h
- Re: [Xen-devel] [v3,11/41] mips: reuse asm-generic/barrier.h
- Re: [Xen-devel] [v3,11/41] mips: reuse asm-generic/barrier.h
- Re: [Xen-devel] [v3,11/41] mips: reuse asm-generic/barrier.h
- Re: [Xen-devel] [v3,11/41] mips: reuse asm-generic/barrier.h
- Re: [Xen-devel] [v3,11/41] mips: reuse asm-generic/barrier.h
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