Re: [PATCH 6/8] i386: bitops: Don't mark memory as clobbered unnecessarily

[Andi Kleen]

> Yes, but _that_ address (of the bit-string) is protected already -- by the
> implicit memory barrier due to the LOCK prefix.

Compiler barrier != CPU barrier.

The memory clobber is a compiler barrier that prevents its global optimizer
from moving memory references. The CPU memory ordering guarantees are completely 
independent from this.


> We shouldn't really be 
> caring about any other memory addresses, so it doesn't affect the
> correctness of the bitops API at all.

The problem is the relationship to other operations.

This is not theoretic and we have had bugs because of this.

-Andi

 
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