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    Subjectsequence lock in Linux
    Hi Paul,

    (CCing lkml)

    Is it just me, or the following code:

    static __always_inline unsigned read_seqbegin(const seqlock_t *sl)
    {
    unsigned ret;

    repeat:
    ret = sl->sequence;
    smp_rmb();
    if (unlikely(ret & 1)) {
    cpu_relax();
    goto repeat;
    }

    return ret;
    }

    could use a ACCESS_ONCE() around the sl->sequence read ? I'm concerned about the
    compiler generating code that reads the sequence number chunkwise.

    The same apply to all other reads of the sequence number in seqlock.h (including
    the retry code).

    Thoughts ?

    Mathieu

    --
    Mathieu Desnoyers
    Operating System Efficiency R&D Consultant
    EfficiOS Inc.
    http://www.efficios.com


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