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    SubjectRe: [PATCH 1/4] drivers edac fix reset edac_mc pollmsec
    On Wed, 25 Jul 2007 14:54:21 -0600 dougthompson@xmission.com wrote:

    > +void edac_mc_reset_delay_period(int value)
    > {
    > - /* cancel the current workq request */
    > - edac_mc_workq_teardown(mci);
    > + struct mem_ctl_info *mci;
    > + struct list_head *item;
    > +
    > + mutex_lock(&mem_ctls_mutex);
    > +
    > + /* scan the list and turn off all workq timers, doing so under lock
    > + */
    > + list_for_each(item, &mc_devices) {
    > + mci = list_entry(item, struct mem_ctl_info, link);
    > +
    > + if (mci->op_state == OP_RUNNING_POLL)
    > + cancel_delayed_work(&mci->work);
    > + }
    > +
    > + mutex_unlock(&mem_ctls_mutex);

    cancel_delayed_work() on its own looks a bit racy. The work could
    presently be running on another CPU.

    So generally we'll run flush_workqueue() or cancel_work_sync() after the
    cancel_delayed_work() to make sure that it has really gone away.

    Beware however that you're holding a lock here. If any of the work
    functions which can be at mci->work also take mem_ctls_mutex then it is
    deadlocky to run flush_workqueue() or cancel_work_sync() while holding that
    lock.

    -
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