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    SubjectRe: Linux 2.6.25-rc2
    On Feb 19, 2008 5:20 PM, Linus Torvalds <torvalds@linux-foundation.org> wrote:
    > So:
    > - it might be something else entirely
    > - it might still be the local cmpxchg, just Torsten didn't happen to
    > notice it until later.

    My new hackbench-testcase also killed 2.6.24-rc2-mm1, so I really
    noticed to late.

    > - it might still be the local cmpxchg, but something else changed its
    > patterns to actually make it start triggering.
    >
    > and in general I don't think we should revert it unless we have stronger
    > indications that it really is the problem (eg somebody finds the actual
    > bug, or a reporter can confirm that it goes away when the local cmpxchg
    > optimization is disabled).

    I tried the following three patches:

    switching the barrier() for a smp_mb() in 2.6.25-rc2-mm1:
    -> crashed

    reverting the FASTPATH-patch in 2.6.25-rc2:
    -> worked

    only removed FAST_CMPXCHG_LOCAL from arch/x86/Kconfig
    -> worked

    So all of these tests seem to confirm, that the bug is in the new SLUB fastpath.

    Torsten


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