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    SubjectRe: barriers: was: [RFC PATCH v2 17/18] livepatch: change to a per-task consistency model
    On Wed, May 04, 2016 at 02:39:40PM +0200, Petr Mladek wrote:
    > > + * This barrier also ensures that if another CPU goes through the
    > > + * syscall barrier, sees the TIF_PATCH_PENDING writes in
    > > + * klp_start_transition(), and calls klp_patch_task(), it also sees the
    > > + * above write to the target state. Otherwise it can put the task in
    > > + * the wrong universe.
    > > + */
    >
    > By other words, it makes sure that klp_patch_task() will assign the
    > right patch_state. Where klp_patch_task() could not be called
    > before we set TIF_PATCH_PENDING in klp_start_transition().
    >
    > > + smp_wmb();
    > > +}

    So I've not read the patch; but ending a function with an smp_wmb()
    feels wrong.

    A wmb orders two stores, and I feel both stores should be well visible
    in the same function.

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