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    SubjectRe: [PATCH 0/24] make atomic_read() behave consistently across all architectures
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    From: Linus Torvalds <torvalds@linux-foundation.org>
    Date: Mon, 20 Aug 2007 22:46:47 -0700 (PDT)

    > Ie a "barrier()" is likely _cheaper_ than the code generation downside
    > from using "volatile".

    Assuming GCC were ever better about the code generation badness
    with volatile that has been discussed here, I much prefer
    we tell GCC "this memory piece changed" rather than "every
    piece of memory has changed" which is what the barrier() does.

    I happened to have been scanning a lot of assembler lately to
    track down a gcc-4.2 miscompilation on sparc64, and the barriers
    do hurt quite a bit in some places. Instead of keeping unrelated
    variables around cached in local registers, it reloads everything.
    -
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