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

[Zachary Amsden <zach@vmware.com>]

Nick Piggin wrote:
> Zachary Amsden wrote:
>
>> Similar to the last bug, on set_pte, we don't want the compiler to 
>> re-order
>> the write of the PTE, even in non-SMP configurations, since if the 
>> write of
>> the low word occurs first, the TLB could prefetch a bad highmem 
>> mapping which
>> has been aliased into low memory.
>>
>
> wmb() means that it also orders IO memory. It is no difference for
> i386, but smp_wmb() actually has the right semantics of the abstract
> Linux memory model.

The name is pretty confused.  smp_wmb seems to imply an SMP-only 
barrier, whereas we want here a write barrier on regular memory.  Both 
smp_wmb and wmb() are identical in that they both reduce to barrier 
today, but I confess not to know which one semantically is correct.  
Your call on this patch - it is unecessary, I thought it was more 
semantically correct, but you probably know that better than me.  So, 
drop part 2 of this patch?

Zach