[PATCH v2] sched/cpufreq: fix trigger cpufreq update w/o real rt/deadline tasks running

From: Wanpeng Li
Date: Tue Apr 19 2016 - 20:46:00 EST


From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>

Sometimes update_curr() is called w/o tasks actually running, it is
captured by:

u64 delta_exec = rq_clock_task(rq) - curr->se.exec_start;

We should not trigger cpufreq update in this case for rt/deadline
classes, and this patch fix it.

Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
---
v1 -> v2:
* add From: head

kernel/sched/deadline.c | 8 ++++----
kernel/sched/rt.c | 8 ++++----
2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index affd97e..8f9b5af 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -717,10 +717,6 @@ static void update_curr_dl(struct rq *rq)
if (!dl_task(curr) || !on_dl_rq(dl_se))
return;

- /* Kick cpufreq (see the comment in linux/cpufreq.h). */
- if (cpu_of(rq) == smp_processor_id())
- cpufreq_trigger_update(rq_clock(rq));
-
/*
* Consumed budget is computed considering the time as
* observed by schedulable tasks (excluding time spent
@@ -736,6 +732,10 @@ static void update_curr_dl(struct rq *rq)
return;
}

+ /* kick cpufreq (see the comment in linux/cpufreq.h). */
+ if (cpu_of(rq) == smp_processor_id())
+ cpufreq_trigger_update(rq_clock(rq));
+
schedstat_set(curr->se.statistics.exec_max,
max(curr->se.statistics.exec_max, delta_exec));

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index c41ea7a..19e1306 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -953,14 +953,14 @@ static void update_curr_rt(struct rq *rq)
if (curr->sched_class != &rt_sched_class)
return;

- /* Kick cpufreq (see the comment in linux/cpufreq.h). */
- if (cpu_of(rq) == smp_processor_id())
- cpufreq_trigger_update(rq_clock(rq));
-
delta_exec = rq_clock_task(rq) - curr->se.exec_start;
if (unlikely((s64)delta_exec <= 0))
return;

+ /* Kick cpufreq (see the comment in linux/cpufreq.h). */
+ if (cpu_of(rq) == smp_processor_id())
+ cpufreq_trigger_update(rq_clock(rq));
+
schedstat_set(curr->se.statistics.exec_max,
max(curr->se.statistics.exec_max, delta_exec));

--
1.9.1