Re: [rfc][patch] i386: remove comment about barriers
From: David Howells
Date: Mon Oct 01 2007 - 09:21:29 EST
Nick Piggin <npiggin@xxxxxxx> wrote:
> [ This is true for x86's sfence/lfence, but raises a question about Linux's
> memory barriers. Does anybody expect that a sequence of smp_wmb and smp_rmb
> would ever provide a full smp_mb barrier? I've always assumed no, but I
> don't know if it is actually documented? ]
I think you have to assume that smp_wmb() only orders stores and write
barriers, and that smp_rmb() only orders reads and read barriers.
smp_mb() implies both smp_wmb() and smp_rmb(), but is greater than the
combination of the two.
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