Messages in this thread | | | Date | Wed, 19 Feb 2014 11:07:30 +0100 | From | Juri Lelli <> | Subject | Re: [PATCH] sched/deadline: Update total bandwidth when adding new task |
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On 02/19/2014 03:56 AM, Steven Rostedt wrote: > While debugging the crash with the bad nr_running accounting, I hit > another bug where, after running my sched deadline test, I was getting > failures to take a CPU offline. It was giving me a -EBUSY error. > > Adding a bunch of trace_printk()s around, I found that the cpu > notifier that called sched_cpu_inactive() was returning a failure. The > overflow value was coming up negative? > > Adding more trace_printk()s, I found that task_dead_dl() function was > subtracting the exact amount that was keeping the CPU from going > offline. I then realized that the task_dead_dl() was updating the > total_bw for the task that was going away, but there was nothing that > added to the total_bw when the task came alive.
We call __dl_add() from dl_overflow(), right before calling __setscheduler().
> If total_bw is not > zero for a CPU, it will keep that CPU from going offline. > > Signed-off-by: Steven Rostedt <rostedt@goodmis.org> > --- > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index b46131e..17f4830 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -3178,6 +3178,7 @@ static void > __setparam_dl(struct task_struct *p, const struct sched_attr *attr) > { > struct sched_dl_entity *dl_se = &p->dl; > + struct dl_bw *dl_b = dl_bw_of(task_cpu(p)); > > init_dl_task_timer(dl_se); > dl_se->dl_runtime = attr->sched_runtime; > @@ -3187,6 +3188,7 @@ __setparam_dl(struct task_struct *p, const struct sched_attr *attr) > dl_se->dl_bw = to_ratio(dl_se->dl_period, dl_se->dl_runtime); > dl_se->dl_throttled = 0; > dl_se->dl_new = 1; > + __dl_add(dl_b, dl_se->dl_bw); > }
This is intended to set params for a task that is going to become -deadline. I don't think it is the right place to update dl_b. And it seems you add it twice (inside dl_overflow and inside __setscheduler).
I performed some tests, and it seems that dl_b is updated correctly, once when the task is started and once when task_dead_dl() is called.
That said, I'm still testing with your stress-cpu-hotplug.
Thanks,
- Juri
> > /* Actually do priority change: must hold pi & rq lock. */ >
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