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sched, rt: Update rq clock when unthrottling of an otherwise idle CPU

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If an RT task is awakened while it's rt_rq is throttled, the time between
wakeup/enqueue and unthrottle/selection may be accounted as rt_time
if the CPU is idle.  Set rq->skip_clock_update negative upon throttle
release to tell put_prev_task() that we need a clock update.

Reported-by: Thomas Giesel <skoe@directbox.com>
Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1304059010.7472.1.camel@marge.simson.net
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Mike Galbraith 2011-04-29 08:36:50 +02:00 committed by Ingo Molnar
parent 3e51e3edfd
commit 61eadef6a9
2 changed files with 10 additions and 3 deletions
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6
kernel/sched.c
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@ -466,7 +466,7 @@ struct rq {
u64 nohz_stamp;
unsigned char nohz_balance_kick;
#endif
unsigned int skip_clock_update;
int skip_clock_update;
/* capture load from *all* tasks on this cpu: */
struct load_weight load;
@ -652,7 +652,7 @@ static void update_rq_clock(struct rq *rq)
{
s64 delta;
if (rq->skip_clock_update)
if (rq->skip_clock_update > 0)
return;
delta = sched_clock_cpu(cpu_of(rq)) - rq->clock;
@ -4127,7 +4127,7 @@ static inline void schedule_debug(struct task_struct *prev)
static void put_prev_task(struct rq *rq, struct task_struct *prev)
{
if (prev->on_rq)
if (prev->on_rq || rq->skip_clock_update < 0)
update_rq_clock(rq);
prev->sched_class->put_prev_task(rq, prev);
}

7
kernel/sched_rt.c
View File

@ -562,6 +562,13 @@ static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun)
if (rt_rq->rt_throttled && rt_rq->rt_time < runtime) {
rt_rq->rt_throttled = 0;
enqueue = 1;
/*
* Force a clock update if the CPU was idle,
* lest wakeup -> unthrottle time accumulate.
*/
if (rt_rq->rt_nr_running && rq->curr == rq->idle)
rq->skip_clock_update = -1;
}
if (rt_rq->rt_time || rt_rq->rt_nr_running)
idle = 0;