On Thu, May 17, 2018 at 09:16:43AM +0200, Vincent Guittot wrote:
With commit
8f111bc357aa ("cpufreq/schedutil: Rewrite CPUFREQ_RT support")
schedutil governor uses rq->rt.rt_nr_running to detect whether a RT task is currently running on the CPU and to set frequency to max if necessary.
cpufreq_update_util() is called in enqueue/dequeue_top_rt_rq() but rq->rt.rt_nr_running as not been updated yet when dequeue_top_rt_rq() is called so schedutil still considers that a RT task is running when the last task is dequeued. The update of rq->rt.rt_nr_running happens later in dequeue_rt_stack()
Fixes: 8f111bc357aa ('cpufreq/schedutil: Rewrite CPUFREQ_RT support') Cc: stable@vger.kernel.org # v4.16+ Signed-off-by: Vincent Guittot vincent.guittot@linaro.org
- v2:
- remove blank line
kernel/sched/rt.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index 7aef6b4..a9f1119 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -1000,9 +1000,6 @@ dequeue_top_rt_rq(struct rt_rq *rt_rq) sub_nr_running(rq, rt_rq->rt_nr_running); rt_rq->rt_queued = 0;
- /* Kick cpufreq (see the comment in kernel/sched/sched.h). */
- cpufreq_update_util(rq, 0);
} static void @@ -1288,6 +1285,9 @@ static void dequeue_rt_stack(struct sched_rt_entity *rt_se, unsigned int flags) if (on_rt_rq(rt_se)) __dequeue_rt_entity(rt_se, flags); }
- /* Kick cpufreq (see the comment in kernel/sched/sched.h). */
- cpufreq_update_util(rq_of_rt_rq(rt_rq_of_se(back)), 0);
}
Hurm.. I think this is also wrong. See how dequeue_rt_stack() is also called from the enqueue path. Also, nothing calls cpufreq_update_util() on the throttle path now.
And talking about throttle; I think we wanted to check rt_queued in that case.
How about the below?
--- kernel/sched/cpufreq_schedutil.c | 2 +- kernel/sched/rt.c | 24 ++++++++++++++---------- kernel/sched/sched.h | 5 +++++ 3 files changed, 20 insertions(+), 11 deletions(-)
diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c index e13df951aca7..1751f9630e49 100644 --- a/kernel/sched/cpufreq_schedutil.c +++ b/kernel/sched/cpufreq_schedutil.c @@ -185,7 +185,7 @@ static unsigned long sugov_aggregate_util(struct sugov_cpu *sg_cpu) struct rq *rq = cpu_rq(sg_cpu->cpu); unsigned long util;
- if (rq->rt.rt_nr_running) { + if (rt_rq_is_runnable(&rq->rt)) { util = sg_cpu->max; } else { util = sg_cpu->util_dl; diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index 7aef6b4e885a..a1108a7da777 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -979,8 +979,14 @@ static void update_curr_rt(struct rq *rq) if (sched_rt_runtime(rt_rq) != RUNTIME_INF) { raw_spin_lock(&rt_rq->rt_runtime_lock); rt_rq->rt_time += delta_exec; - if (sched_rt_runtime_exceeded(rt_rq)) + if (sched_rt_runtime_exceeded(rt_rq)) { + struct rq *rq = rq_of_rt_rq(rt_rq); + + if (&rq->rt == rt_rq) + cpufreq_update_util(rq, 0); + resched_curr(rq); + } raw_spin_unlock(&rt_rq->rt_runtime_lock); } } @@ -1000,9 +1006,6 @@ dequeue_top_rt_rq(struct rt_rq *rt_rq)
sub_nr_running(rq, rt_rq->rt_nr_running); rt_rq->rt_queued = 0; - - /* Kick cpufreq (see the comment in kernel/sched/sched.h). */ - cpufreq_update_util(rq, 0); }
static void @@ -1019,9 +1022,6 @@ enqueue_top_rt_rq(struct rt_rq *rt_rq)
add_nr_running(rq, rt_rq->rt_nr_running); rt_rq->rt_queued = 1; - - /* Kick cpufreq (see the comment in kernel/sched/sched.h). */ - cpufreq_update_util(rq, 0); }
#if defined CONFIG_SMP @@ -1330,6 +1330,8 @@ enqueue_task_rt(struct rq *rq, struct task_struct *p, int flags)
if (!task_current(rq, p) && p->nr_cpus_allowed > 1) enqueue_pushable_task(rq, p); + + cpufreq_update_util(rq, 0); }
static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int flags) @@ -1340,6 +1342,8 @@ static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int flags) dequeue_rt_entity(rt_se, flags);
dequeue_pushable_task(rq, p); + + cpufreq_update_util(rq, 0); }
/* @@ -1533,6 +1537,9 @@ pick_next_task_rt(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) struct task_struct *p; struct rt_rq *rt_rq = &rq->rt;
+ if (!rt_rq->rt_queued) + return NULL; + if (need_pull_rt_task(rq, prev)) { /* * This is OK, because current is on_cpu, which avoids it being @@ -1560,9 +1567,6 @@ pick_next_task_rt(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) if (prev->sched_class == &rt_sched_class) update_curr_rt(rq);
- if (!rt_rq->rt_queued) - return NULL; - put_prev_task(rq, prev);
p = _pick_next_task_rt(rq); diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index c9895d35c5f7..bec7f2eecaf3 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -609,6 +609,11 @@ struct rt_rq { #endif };
+static inline bool rt_rq_is_runnable(struct rt_rq *rt_rq) +{ + return rq_rq->rt_queued && rt_rq->rt_nr_running; +} + /* Deadline class' related fields in a runqueue */ struct dl_rq { /* runqueue is an rbtree, ordered by deadline */