Messages in this thread | | | Date | Wed, 26 Apr 2006 18:09:59 -0700 | From | Zachary Amsden <> | Subject | Re: [PATCH 2/2] I386 convert pae wmb to non smp |
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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?
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