On Fri, Jan 22, 2021 at 08:17:01PM -0500, Joel Fernandes (Google) wrote: > +static void sched_core_update_cookie(struct task_struct *p, unsigned long > cookie, > + enum sched_core_cookie_type cookie_type) > +{ > + struct rq_flags rf; > + struct rq *rq; > + > + if (!p) > + return; > + > + rq = task_rq_lock(p, &rf); > + > + switch (cookie_type) { > + case sched_core_task_cookie_type: > + p->core_task_cookie = cookie; > + break; > + case sched_core_group_cookie_type: > + p->core_group_cookie = cookie; > + break; > + default: > + WARN_ON_ONCE(1); > + } > + > + /* Set p->core_cookie, which is the overall cookie */ > + __sched_core_update_cookie(p); > + > + if (sched_core_enqueued(p)) { > + sched_core_dequeue(rq, p); > + if (!p->core_cookie) { > + task_rq_unlock(rq, p, &rf); > + return; > + } > + } > + > + if (sched_core_enabled(rq) && > + p->core_cookie && task_on_rq_queued(p)) > + sched_core_enqueue(task_rq(p), p); > + > + /* > + * If task is currently running or waking, it may not be compatible > + * anymore after the cookie change, so enter the scheduler on its CPU > + * to schedule it away. > + */ > + if (task_running(rq, p) || p->state == TASK_WAKING) > + resched_curr(rq);
I'm not immediately seeing the need for that WAKING test. Since we're holding it's rq->lock, the only place that task can be WAKING is on the wake_list. And if it's there, it needs to acquire rq->lock to get enqueued, and rq->lock again to get scheduled. What am I missing? > + > + task_rq_unlock(rq, p, &rf); > +}