Re: [PATCH 2/2] I386 convert pae wmb to non smp

[Keir Fraser <Keir.Fraser@cl.cam.ac.uk>]

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