Messages in this thread | | | Date | Fri, 16 Mar 2018 10:51:13 +0100 | From | Peter Zijlstra <> | Subject | Re: update vruntime incorrectly When use rt_mutex |
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On Thu, Mar 15, 2018 at 03:36:10PM +0800, Kathleen Chang wrote: > hi, > > We found the vruntime might update incorrectly when use rt_mutex.
That's nice, on what kernel?
Also, your email is very hard to make sense of.
> <<abnormal case>> > When the Task is waking, update vruntime incorrectly. > 1. When there is a CFS task (A) hold rt_mutex_lock and the state is > TASK_WAKING (on_rq=0), a RT task (B) want to hold this rt_mutex_lock. > Update vruntime incorrectly. > > RT task (B) > rt_mutex_setprio (cfs->RT) -> Task is waking , and update > vruntime > > queued = task_on_rq_queued(p); // task is waking, queued=0 > running = task_current(rq, p); > if (queued) /* don't update vruntime here! */ > dequeue_task(rq, p, queue_flag); > if (running) > put_prev_task(rq, p); > > check_class_changed(rq, p, prev_class, oldprio); -> > switched_from_fair -> > detach_task_cfs_rq > ( due to task is waking, and bypass > vruntime-=cfs_rq.min_vruntime) > > static void detach_task_cfs_rq(struct task_struct *p) > { > struct sched_entity *se = &p->se; > struct cfs_rq *cfs_rq = cfs_rq_of(se); > > if (!vruntime_normalized(p)) { // return 1, then p->state is > TASK_WAKING > /* > * Fix up our vruntime so that the current sleep doesn't > * cause 'unlimited' sleep bonus. > */ > place_entity(cfs_rq, se, 0); > check_vruntime(8, se, cfs_rq->min_vruntime); > se->vruntime -= cfs_rq->min_vruntime;
So here we subtract min_vruntime,
> se->normalized = true;
this doesn't exist.. which makes me wonder what you're looking at,
> } > > detach_entity_cfs_rq(se); > } > > // when p->state is TASK_WAKING, the task's vruntime is normalized > static inline bool vruntime_normalized(struct task_struct *p) > { > ..... > if (!se->sum_exec_runtime || p->state == TASK_WAKING) > return true; > > } > > 2. When the task (A) which holds the rt_muex_lock unlock the > rt_mutex_lock. > Task (A) must be on_rq=1 > > rt_mutex_setprio (RT->CFS) > if (queued) > enqueue_task(rq, p, queue_flag); ); > /* vruntime += cfs_rq.min_vruntime */
And here we're adding min_vruntime.
> if (running) > set_curr_task(rq, p); > > that result in vruntime accumulates
So what exactly is the problem?
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