On 09/17, Peter Zijlstra wrote: > > Included in it are some of the details on this subject, because a wakeup > has two prior states that are of importance, the tasks own prior state > and the wakeup state, both should be considered in the 'program order' > flow. Great. Just one question, > + * BLOCKING -- aka. SLEEP + WAKEUP > + * > + * For blocking things are a little more interesting, because when we dequeue > + * the task, we don't need to acquire the old rq lock in order to migrate it. > + * > + * Say CPU0 does a wait_event() and CPU1 does the wake() and migrates the task > + * to CPU2 (the most complex example): > + * > + * CPU0 (schedule) CPU1 (try_to_wake_up) CPU2 (sched_ttwu_pending) > + * > + * X->state = UNINTERRUPTIBLE > + * MB > + * if (cond) > + * break > + * cond = true > + * > + * WMB WMB (aka smp_mb__before_spinlock) Yes, both CPU's do WMB-aka-smp_mb__before_spinlock... But afaics in this particular case we do not really need them? So perhaps we should not even mention them? Because (if I am right) this can confuse the reader who will try to understand how/where do we rely on these barriers. Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
