Messages in this thread | | | From | Keir Fraser <> | Subject | Re: [PATCH 2/2] I386 convert pae wmb to non smp | Date | Thu, 27 Apr 2006 09:21:54 +0100 |
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On 27 Apr 2006, at 04:30, Nick Piggin wrote:
>> The name is pretty confused. smp_wmb seems to imply an SMP-only >> barrier, whereas we want here a write barrier on regular memory. > > That is just a compiler barrier (barrier()). A CPU should always be > consistent with > itself so memory ordering doesn't really apply there (hence smp_ > prefix, which also > are compiler barriers, of course).
This would be an issue of consistency between a CPU and its TLB, so I doubt the usual self-consistency argument would hold. I would consider the TLB as logically external and separate from the core execution logic of the CPU. Of course it's an academic point either way since no PAE-capable x86 processor ever reorders stores to WB memory -- my original point was simply that smp_wmb() is a misleading name in this context, even barrier() would be clearer imo, but I'm in no way a Linux abstract memory model expert.
-- Keir
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