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    SubjectRE: Fix unlock_buffer() to work the same way as bit_unlock()
    Date
    Nick Piggin wrote on Tuesday, March 28, 2006 12:11 AM
    > OK, that's fair enough and I guess you do need a barrier there.
    > However, should the mb__after barrier still remain? The comment
    > in wake_up_bit suggests yes, and there is similar code in
    > unlock_page.

    Question on unlock_page:

    void fastcall unlock_page(struct page *page)
    {
    smp_mb__before_clear_bit();
    if (!TestClearPageLocked(page))
    BUG();
    smp_mb__after_clear_bit();
    wake_up_page(page, PG_locked);
    }

    Assuming test_and_clear_bit() on all arch does what the API is
    called for with full memory fence around the atomic op, why do
    you need smp_mb__before_clear_bit and smp_mb__after_clear_bit?
    Aren't they redundant?

    - Ken
    -
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