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    SubjectRe: [PATCH 0/24] make atomic_read() behave consistently across all architectures
    On Thu, Aug 16, 2007 at 09:34:41AM -0700, Paul E. McKenney wrote:
    >
    > The compiler can also reorder non-volatile accesses. For an example
    > patch that cares about this, please see:
    >
    > http://lkml.org/lkml/2007/8/7/280
    >
    > This patch uses an ORDERED_WRT_IRQ() in rcu_read_lock() and
    > rcu_read_unlock() to ensure that accesses aren't reordered with respect
    > to interrupt handlers and NMIs/SMIs running on that same CPU.

    Good, finally we have some code to discuss (even though it's
    not actually in the kernel yet).

    First of all, I think this illustrates that what you want
    here has nothing to do with atomic ops. The ORDERED_WRT_IRQ
    macro occurs a lot more times in your patch than atomic
    reads/sets. So *assuming* that it was necessary at all,
    then having an ordered variant of the atomic_read/atomic_set
    ops could do just as well.

    However, I still don't know which atomic_read/atomic_set in
    your patch would be broken if there were no volatile. Could
    you please point them out?

    Cheers,
    --
    Visit Openswan at http://www.openswan.org/
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