Re: [Xen-devel] [PATCH 2/3] xen/arm64: resync atomics and spinlock asm with Linux

[Will Deacon <will.deacon@xxxxxxx>]

On Mon, Jul 29, 2013 at 05:13:02PM +0100, Ian Campbell wrote:
> On Mon, 2013-07-29 at 17:02 +0100, Tim Deegan wrote:
> > But I don't understand the new 'memory' clobbers around in this patch.
> > Or rather, I don't understand why there are memory clobbers but not
> > DMBs.

The acquire/release instructions imply half barriers, but GCC may still
re-order instructions across them unless we include the memory clobber.

Will

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