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    SubjectRe: [PATCH] splice : two smp_mb() can be omitted
    On Tue, Oct 31 2006, Eric Dumazet wrote:
    > This patch deletes two calls to smp_mb() that were done after
    > mutex_unlock() that contains an implicit memory barrier.
    >
    > The first one in splice_to_pipe(), where 'do_wakeup' is set to true only if
    > pipe->inode is set (and in this case the
    > if (pipe->inode)
    > mutex_unlock(&pipe->inode->i_mutex);
    > is done too)
    >
    > The second one in link_pipe(), following inode_double_unlock() that
    > contains calls to mutex_unlock() too.

    NAK on that patch, the smp_mb() follows the waitqueue_active(). If you
    later change the code and move the locks or whatnot, you have lost that
    connection.

    If you change the patch to insert a comment, then it may be more
    applicable.

    --
    Jens Axboe

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