Messages in this thread | | | From | Nick Piggin <> | Subject | Re: Intel Memory Ordering White Paper | Date | Sat, 8 Sep 2007 06:46:56 +1000 |
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On Saturday 08 September 2007 20:30, Alan Cox wrote: > On Sat, 8 Sep 2007 18:54:57 +1000 > > Nick Piggin <nickpiggin@yahoo.com.au> wrote: > > On Saturday 08 September 2007 08:26, Jesse Barnes wrote: > > > FYI, we just released a new white paper describing memory ordering for > > > Intel processors: > > > http://developer.intel.com/products/processor/manuals/index.htm > > > > > > Should help answer some questions about some of the ordering primitives > > > we use on i386 and x86_64. > > > > So, can we finally noop smp_rmb and smp_wmb on x86? > > Nakked-by: Alan Cox <alan@redhat.com> > > You can only no-op it on 64bit Intel processors. On 32bit it needs to be > conditional on whether your processor family (or back compat for it) as > the Pentium Pro has some serious store ordering errata (hence the way it > needs lock decb for spin_unlock)
We already noop smp_wmb on i386 even when CONFIG_X86_PPRO_FENCE.
I'm not sure if either errata can be solved completely by adding lock ops in barrier instructions anyway: they both seem to involve situations where there is just a single problematic cacheline in question. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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