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Message-ID: <lsq.1465842997.770266816@decadent.org.uk>
Date: Mon, 13 Jun 2016 19:36:37 +0100
From: Ben Hutchings <ben@...adent.org.uk>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC: akpm@...ux-foundation.org, rostedt@...dmis.org,
ktkhai@...allels.com, wanpeng.li@...ux.intel.com, oleg@...hat.com,
"Thomas Gleixner" <tglx@...utronix.de>,
"Byungchul Park" <byungchul.park@....com>,
umgwanakikbuti@...il.com, juri.lelli@...il.com,
pang.xunlei@...aro.org, "Peter Zijlstra" <peterz@...radead.org>
Subject: [PATCH 3.16 109/114] sched: Replace post_schedule with a balance
callback list
3.16.36-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Peter Zijlstra <peterz@...radead.org>
commit e3fca9e7cbfb72694a21c886fcdf9f059cfded9c upstream.
Generalize the post_schedule() stuff into a balance callback list.
This allows us to more easily use it outside of schedule() and cross
sched_class.
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: ktkhai@...allels.com
Cc: rostedt@...dmis.org
Cc: juri.lelli@...il.com
Cc: pang.xunlei@...aro.org
Cc: oleg@...hat.com
Cc: wanpeng.li@...ux.intel.com
Cc: umgwanakikbuti@...il.com
Link: http://lkml.kernel.org/r/20150611124742.424032725@infradead.org
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
[Conflicts: kernel/sched/core.c]
Signed-off-by: Byungchul Park <byungchul.park@....com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
kernel/sched/core.c | 36 ++++++++++++++++++++++++------------
kernel/sched/deadline.c | 21 +++++++++++----------
kernel/sched/rt.c | 25 +++++++++++--------------
kernel/sched/sched.h | 19 +++++++++++++++++--
4 files changed, 63 insertions(+), 38 deletions(-)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2258,23 +2258,35 @@ static void finish_task_switch(struct rq
#ifdef CONFIG_SMP
/* rq->lock is NOT held, but preemption is disabled */
-static inline void post_schedule(struct rq *rq)
+static void __balance_callback(struct rq *rq)
{
- if (rq->post_schedule) {
- unsigned long flags;
+ struct callback_head *head, *next;
+ void (*func)(struct rq *rq);
+ unsigned long flags;
- raw_spin_lock_irqsave(&rq->lock, flags);
- if (rq->curr->sched_class->post_schedule)
- rq->curr->sched_class->post_schedule(rq);
- raw_spin_unlock_irqrestore(&rq->lock, flags);
+ raw_spin_lock_irqsave(&rq->lock, flags);
+ head = rq->balance_callback;
+ rq->balance_callback = NULL;
+ while (head) {
+ func = (void (*)(struct rq *))head->func;
+ next = head->next;
+ head->next = NULL;
+ head = next;
- rq->post_schedule = 0;
+ func(rq);
}
+ raw_spin_unlock_irqrestore(&rq->lock, flags);
+}
+
+static inline void balance_callback(struct rq *rq)
+{
+ if (unlikely(rq->balance_callback))
+ __balance_callback(rq);
}
#else
-static inline void post_schedule(struct rq *rq)
+static inline void balance_callback(struct rq *rq)
{
}
@@ -2295,7 +2307,7 @@ asmlinkage __visible void schedule_tail(
* FIXME: do we need to worry about rq being invalidated by the
* task_switch?
*/
- post_schedule(rq);
+ balance_callback(rq);
#ifdef __ARCH_WANT_UNLOCKED_CTXSW
/* In this case, finish_task_switch does not reenable preemption */
@@ -2822,7 +2834,7 @@ need_resched:
} else
raw_spin_unlock_irq(&rq->lock);
- post_schedule(rq);
+ balance_callback(rq);
sched_preempt_enable_no_resched();
if (need_resched())
@@ -7001,7 +7013,7 @@ void __init sched_init(void)
rq->sd = NULL;
rq->rd = NULL;
rq->cpu_capacity = SCHED_CAPACITY_SCALE;
- rq->post_schedule = 0;
+ rq->balance_callback = NULL;
rq->active_balance = 0;
rq->next_balance = jiffies;
rq->push_cpu = 0;
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -213,9 +213,16 @@ static inline bool need_pull_dl_task(str
return dl_task(prev);
}
-static inline void set_post_schedule(struct rq *rq)
+static DEFINE_PER_CPU(struct callback_head, dl_balance_head);
+
+static void push_dl_tasks(struct rq *);
+
+static inline void queue_push_tasks(struct rq *rq)
{
- rq->post_schedule = has_pushable_dl_tasks(rq);
+ if (!has_pushable_dl_tasks(rq))
+ return;
+
+ queue_balance_callback(rq, &per_cpu(dl_balance_head, rq->cpu), push_dl_tasks);
}
#else
@@ -250,7 +257,7 @@ static inline int pull_dl_task(struct rq
return 0;
}
-static inline void set_post_schedule(struct rq *rq)
+static inline void queue_push_tasks(struct rq *rq)
{
}
#endif /* CONFIG_SMP */
@@ -1043,7 +1050,7 @@ struct task_struct *pick_next_task_dl(st
start_hrtick_dl(rq, p);
#endif
- set_post_schedule(rq);
+ queue_push_tasks(rq);
return p;
}
@@ -1452,11 +1459,6 @@ skip:
return ret;
}
-static void post_schedule_dl(struct rq *rq)
-{
- push_dl_tasks(rq);
-}
-
/*
* Since the task is not running and a reschedule is not going to happen
* anytime soon on its runqueue, we try pushing it away now.
@@ -1644,7 +1646,6 @@ const struct sched_class dl_sched_class
.set_cpus_allowed = set_cpus_allowed_dl,
.rq_online = rq_online_dl,
.rq_offline = rq_offline_dl,
- .post_schedule = post_schedule_dl,
.task_woken = task_woken_dl,
#endif
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -338,13 +338,16 @@ static inline int has_pushable_tasks(str
return !plist_head_empty(&rq->rt.pushable_tasks);
}
-static inline void set_post_schedule(struct rq *rq)
+static DEFINE_PER_CPU(struct callback_head, rt_balance_head);
+
+static void push_rt_tasks(struct rq *);
+
+static inline void queue_push_tasks(struct rq *rq)
{
- /*
- * We detect this state here so that we can avoid taking the RQ
- * lock again later if there is no need to push
- */
- rq->post_schedule = has_pushable_tasks(rq);
+ if (!has_pushable_tasks(rq))
+ return;
+
+ queue_balance_callback(rq, &per_cpu(rt_balance_head, rq->cpu), push_rt_tasks);
}
static void enqueue_pushable_task(struct rq *rq, struct task_struct *p)
@@ -401,7 +404,7 @@ static inline int pull_rt_task(struct rq
return 0;
}
-static inline void set_post_schedule(struct rq *rq)
+static inline void queue_push_tasks(struct rq *rq)
{
}
#endif /* CONFIG_SMP */
@@ -1472,7 +1475,7 @@ pick_next_task_rt(struct rq *rq, struct
if (p)
dequeue_pushable_task(rq, p);
- set_post_schedule(rq);
+ queue_push_tasks(rq);
return p;
}
@@ -1852,11 +1855,6 @@ skip:
return ret;
}
-static void post_schedule_rt(struct rq *rq)
-{
- push_rt_tasks(rq);
-}
-
/*
* If we are not running and we are not going to reschedule soon, we should
* try to push tasks away now
@@ -2128,7 +2126,6 @@ const struct sched_class rt_sched_class
.set_cpus_allowed = set_cpus_allowed_rt,
.rq_online = rq_online_rt,
.rq_offline = rq_offline_rt,
- .post_schedule = post_schedule_rt,
.task_woken = task_woken_rt,
.switched_from = switched_from_rt,
#endif
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -569,9 +569,10 @@ struct rq {
unsigned long cpu_capacity;
+ struct callback_head *balance_callback;
+
unsigned char idle_balance;
/* For active balancing */
- int post_schedule;
int active_balance;
int push_cpu;
struct cpu_stop_work active_balance_work;
@@ -670,6 +671,21 @@ extern int migrate_swap(struct task_stru
#ifdef CONFIG_SMP
+static inline void
+queue_balance_callback(struct rq *rq,
+ struct callback_head *head,
+ void (*func)(struct rq *rq))
+{
+ lockdep_assert_held(&rq->lock);
+
+ if (unlikely(head->next))
+ return;
+
+ head->func = (void (*)(struct callback_head *))func;
+ head->next = rq->balance_callback;
+ rq->balance_callback = head;
+}
+
extern void sched_ttwu_pending(void);
#define rcu_dereference_check_sched_domain(p) \
@@ -1127,7 +1143,6 @@ struct sched_class {
int (*select_task_rq)(struct task_struct *p, int task_cpu, int sd_flag, int flags);
void (*migrate_task_rq)(struct task_struct *p, int next_cpu);
- void (*post_schedule) (struct rq *this_rq);
void (*task_waking) (struct task_struct *task);
void (*task_woken) (struct rq *this_rq, struct task_struct *task);
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