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    SubjectRe: [PATCH 1/4] cpu_stop: implement stop_cpu[s]()
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    On Thu, 2010-04-22 at 18:09 +0200, Tejun Heo wrote:

    > +struct cpu_stop_done {
    > + atomic_t nr_todo; /* nr left to execute */
    > + bool executed; /* actually executed? */
    > + int ret; /* collected return value */
    > + struct completion completion; /* fired if nr_todo reaches 0 */
    > +};
    > +

    > +/* signal completion unless @done is NULL */
    > +static void cpu_stop_signal_done(struct cpu_stop_done *done, bool executed)
    > +{
    > + if (done) {
    > + if (executed)
    > + done->executed = true;
    > + if (atomic_dec_and_test(&done->nr_todo))
    > + complete(&done->completion);
    > + }
    > +}
    > +
    > +/* queue @work to @stopper. if offline, @work is completed immediately */
    > +static void cpu_stop_queue_work(struct cpu_stopper *stopper,
    > + struct cpu_stop_work *work)
    > +{
    > + unsigned long flags;
    > +
    > + spin_lock_irqsave(&stopper->lock, flags);
    > +
    > + if (stopper->enabled) {
    > + list_add_tail(&work->list, &stopper->works);
    > + wake_up_process(stopper->thread);
    > + } else
    > + cpu_stop_signal_done(work->done, false);
    > +
    > + spin_unlock_irqrestore(&stopper->lock, flags);
    > +}
    > +

    > +int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg)
    > +{
    > + struct cpu_stop_done done;
    > + struct cpu_stop_work work = { .fn = fn, .arg = arg, .done = &done };
    > +
    > + cpu_stop_init_done(&done, 1);
    > + cpu_stop_queue_work(&per_cpu(cpu_stopper, cpu), &work);
    > + wait_for_completion(&done.completion);
    > + return done.executed ? done.ret : -ENOENT;
    > +}

    If you do:

    done = { .ret = -ENOENT, };

    And remove that if()

    > + ret = work->fn(work->arg);
    > + if (ret)
    > + done->ret = ret;
    > +

    You can do away with all the ->executed bits.


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