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authorPeter Zijlstra <peterz@infradead.org>2019-11-08 14:16:00 +0100
committerIngo Molnar <mingo@kernel.org>2019-11-11 08:35:21 +0100
commita0e813f26ebcb25c0b5e504498fbd796cca1a4ba (patch)
treec6a926cff783866cc5ee1b20ffefb559e78d45fa /kernel/sched
parent2eeb01a28c9233333bf229a5b4b0559f4bd22b52 (diff)
sched/core: Further clarify sched_class::set_next_task()
It turns out there really is something special to the first set_next_task() invocation. In specific the 'change' pattern really should not cause balance callbacks. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: bsegall@google.com Cc: dietmar.eggemann@arm.com Cc: juri.lelli@redhat.com Cc: ktkhai@virtuozzo.com Cc: mgorman@suse.de Cc: qais.yousef@arm.com Cc: qperret@google.com Cc: rostedt@goodmis.org Cc: valentin.schneider@arm.com Cc: vincent.guittot@linaro.org Fixes: f95d4eaee6d0 ("sched/{rt,deadline}: Fix set_next_task vs pick_next_task") Link: https://lkml.kernel.org/r/20191108131909.775434698@infradead.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/sched')
-rw-r--r--kernel/sched/deadline.c7
-rw-r--r--kernel/sched/fair.c2
-rw-r--r--kernel/sched/idle.c4
-rw-r--r--kernel/sched/rt.c7
-rw-r--r--kernel/sched/sched.h4
-rw-r--r--kernel/sched/stop_task.c4
6 files changed, 17 insertions, 11 deletions
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index f7fbb4427959..43323f875cb9 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1743,13 +1743,16 @@ static void start_hrtick_dl(struct rq *rq, struct task_struct *p)
}
#endif
-static void set_next_task_dl(struct rq *rq, struct task_struct *p)
+static void set_next_task_dl(struct rq *rq, struct task_struct *p, bool first)
{
p->se.exec_start = rq_clock_task(rq);
/* You can't push away the running task */
dequeue_pushable_dl_task(rq, p);
+ if (!first)
+ return;
+
if (hrtick_enabled(rq))
start_hrtick_dl(rq, p);
@@ -1782,7 +1785,7 @@ static struct task_struct *pick_next_task_dl(struct rq *rq)
dl_se = pick_next_dl_entity(rq, dl_rq);
BUG_ON(!dl_se);
p = dl_task_of(dl_se);
- set_next_task_dl(rq, p);
+ set_next_task_dl(rq, p, true);
return p;
}
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index ba97d1a1b976..81eba554db8d 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -10344,7 +10344,7 @@ static void switched_to_fair(struct rq *rq, struct task_struct *p)
* This routine is mostly called to set cfs_rq->curr field when a task
* migrates between groups/classes.
*/
-static void set_next_task_fair(struct rq *rq, struct task_struct *p)
+static void set_next_task_fair(struct rq *rq, struct task_struct *p, bool first)
{
struct sched_entity *se = &p->se;
diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index f88b79eeee1e..428cd05c0b5d 100644
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -385,7 +385,7 @@ static void put_prev_task_idle(struct rq *rq, struct task_struct *prev)
{
}
-static void set_next_task_idle(struct rq *rq, struct task_struct *next)
+static void set_next_task_idle(struct rq *rq, struct task_struct *next, bool first)
{
update_idle_core(rq);
schedstat_inc(rq->sched_goidle);
@@ -395,7 +395,7 @@ struct task_struct *pick_next_task_idle(struct rq *rq)
{
struct task_struct *next = rq->idle;
- set_next_task_idle(rq, next);
+ set_next_task_idle(rq, next, true);
return next;
}
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 38027c04b04c..e591d40fd645 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1515,13 +1515,16 @@ static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p, int flag
#endif
}
-static inline void set_next_task_rt(struct rq *rq, struct task_struct *p)
+static inline void set_next_task_rt(struct rq *rq, struct task_struct *p, bool first)
{
p->se.exec_start = rq_clock_task(rq);
/* The running task is never eligible for pushing */
dequeue_pushable_task(rq, p);
+ if (!first)
+ return;
+
/*
* If prev task was rt, put_prev_task() has already updated the
* utilization. We only care of the case where we start to schedule a
@@ -1572,7 +1575,7 @@ static struct task_struct *pick_next_task_rt(struct rq *rq)
return NULL;
p = _pick_next_task_rt(rq);
- set_next_task_rt(rq, p);
+ set_next_task_rt(rq, p, true);
return p;
}
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 75d96cce1492..05c282775f21 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1716,7 +1716,7 @@ struct sched_class {
struct task_struct *(*pick_next_task)(struct rq *rq);
void (*put_prev_task)(struct rq *rq, struct task_struct *p);
- void (*set_next_task)(struct rq *rq, struct task_struct *p);
+ void (*set_next_task)(struct rq *rq, struct task_struct *p, bool first);
#ifdef CONFIG_SMP
int (*balance)(struct rq *rq, struct task_struct *prev, struct rq_flags *rf);
@@ -1768,7 +1768,7 @@ static inline void put_prev_task(struct rq *rq, struct task_struct *prev)
static inline void set_next_task(struct rq *rq, struct task_struct *next)
{
WARN_ON_ONCE(rq->curr != next);
- next->sched_class->set_next_task(rq, next);
+ next->sched_class->set_next_task(rq, next, false);
}
#ifdef CONFIG_SMP
diff --git a/kernel/sched/stop_task.c b/kernel/sched/stop_task.c
index 0aefdfb79b36..4c9e9975684f 100644
--- a/kernel/sched/stop_task.c
+++ b/kernel/sched/stop_task.c
@@ -29,7 +29,7 @@ check_preempt_curr_stop(struct rq *rq, struct task_struct *p, int flags)
/* we're never preempted */
}
-static void set_next_task_stop(struct rq *rq, struct task_struct *stop)
+static void set_next_task_stop(struct rq *rq, struct task_struct *stop, bool first)
{
stop->se.exec_start = rq_clock_task(rq);
}
@@ -39,7 +39,7 @@ static struct task_struct *pick_next_task_stop(struct rq *rq)
if (!sched_stop_runnable(rq))
return NULL;
- set_next_task_stop(rq, rq->stop);
+ set_next_task_stop(rq, rq->stop, true);
return rq->stop;
}