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Re: [Xen-devel] [v3,11/41] mips: reuse asm-generic/barrier.h
- To: Leonid Yegoshin <Leonid.Yegoshin@xxxxxxxxxx>
- From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
- Date: Tue, 12 Jan 2016 11:25:55 +0100
- Cc: linux-mips@xxxxxxxxxxxxxx, linux-ia64@xxxxxxxxxxxxxxx, "Michael S. Tsirkin" <mst@xxxxxxxxxx>, 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>, Arnd Bergmann <arnd@xxxxxxxx>, linux-sh@xxxxxxxxxxxxxxx, x86@xxxxxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxxx, Ingo Molnar <mingo@xxxxxxx>, linux-xtensa@xxxxxxxxxxxxxxxx, james.hogan@xxxxxxxxxx, user-mode-linux-devel@xxxxxxxxxxxxxxxxxxxxx, Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>, adi-buildroot-devel@xxxxxxxxxxxxxxxxxxxxx, 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, 12 Jan 2016 10:26:26 +0000
- List-id: Xen developer discussion <xen-devel.lists.xen.org>
On Tue, Jan 12, 2016 at 10:27:11AM +0100, Peter Zijlstra wrote:
> 2) the changelog _completely_ fails to explain the sync 0x11 and sync
> 0x12 semantics nor does it provide a publicly accessible link to
> documentation that does.
Ralf pointed me at: https://imgtec.com/mips/architectures/mips64/
> 3) it really should have explained what you did with
> smp_llsc_mb/smp_mb__before_llsc() in _detail_.
And reading the MIPS64 v6.04 instruction set manual, I think 0x11/0x12
are _NOT_ transitive and therefore cannot be used to implement the
smp_mb__{before,after} stuff.
That is, in MIPS speak, those SYNC types are Ordering Barriers, not
Completion Barriers. They need not be globally performed.
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