Re: [PATCH 2/2] I386 convert pae wmb to non smp
From: Zachary Amsden
Date: Wed Apr 26 2006 - 21:10:15 EST
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
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