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Date: Tue, 23 Apr 2019 16:18:14 +0000
From: Vineeth Remanan Pillai <vpillai@...italocean.com>
To: Nishanth Aravamudan <naravamudan@...italocean.com>,
Julien Desfossez <jdesfossez@...italocean.com>,
Peter Zijlstra <peterz@...radead.org>,
Tim Chen <tim.c.chen@...ux.intel.com>, mingo@...nel.org,
tglx@...utronix.de, pjt@...gle.com, torvalds@...ux-foundation.org
Cc: linux-kernel@...r.kernel.org, subhra.mazumdar@...cle.com,
fweisbec@...il.com, keescook@...omium.org, kerrnel@...gle.com,
Phil Auld <pauld@...hat.com>, Aaron Lu <aaron.lwe@...il.com>,
Aubrey Li <aubrey.intel@...il.com>,
Valentin Schneider <valentin.schneider@....com>,
Mel Gorman <mgorman@...hsingularity.net>,
Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
Paolo Bonzini <pbonzini@...hat.com>,
Vineeth Remanan Pillai <vpillai@...italocean.com>
Subject: [RFC PATCH v2 09/17] sched: Introduce sched_class::pick_task()
From: "Peter Zijlstra (Intel)" <peterz@...radead.org>
Because sched_class::pick_next_task() also implies
sched_class::set_next_task() (and possibly put_prev_task() and
newidle_balance) it is not state invariant. This makes it unsuitable
for remote task selection.
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Vineeth Remanan Pillai <vpillai@...italocean.com>
Signed-off-by: Julien Desfossez <jdesfossez@...italocean.com>
---
Changes in v2
-------------
- Fixes a NULL pointer dereference crash
- Subhra Mazumdar
- Tim Chen
---
kernel/sched/deadline.c | 21 ++++++++++++++++-----
kernel/sched/fair.c | 39 ++++++++++++++++++++++++++++++++++++---
kernel/sched/idle.c | 10 +++++++++-
kernel/sched/rt.c | 21 ++++++++++++++++-----
kernel/sched/sched.h | 2 ++
kernel/sched/stop_task.c | 21 ++++++++++++++++-----
6 files changed, 95 insertions(+), 19 deletions(-)
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 249310e68592..010234908cc0 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1723,15 +1723,12 @@ static struct sched_dl_entity *pick_next_dl_entity(struct rq *rq,
return rb_entry(left, struct sched_dl_entity, rb_node);
}
-static struct task_struct *
-pick_next_task_dl(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
+static struct task_struct *pick_task_dl(struct rq *rq)
{
struct sched_dl_entity *dl_se;
struct task_struct *p;
struct dl_rq *dl_rq;
- WARN_ON_ONCE(prev || rf);
-
dl_rq = &rq->dl;
if (unlikely(!dl_rq->dl_nr_running))
@@ -1742,7 +1739,19 @@ pick_next_task_dl(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
p = dl_task_of(dl_se);
- set_next_task_dl(rq, p);
+ return p;
+}
+
+static struct task_struct *
+pick_next_task_dl(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
+{
+ struct task_struct *p;
+
+ WARN_ON_ONCE(prev || rf);
+
+ p = pick_task_dl(rq);
+ if (p)
+ set_next_task_dl(rq, p);
return p;
}
@@ -2389,6 +2398,8 @@ const struct sched_class dl_sched_class = {
.set_next_task = set_next_task_dl,
#ifdef CONFIG_SMP
+ .pick_task = pick_task_dl,
+
.select_task_rq = select_task_rq_dl,
.migrate_task_rq = migrate_task_rq_dl,
.set_cpus_allowed = set_cpus_allowed_dl,
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index c055bad249a9..45d86b862750 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4132,7 +4132,7 @@ pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
* Avoid running the skip buddy, if running something else can
* be done without getting too unfair.
*/
- if (cfs_rq->skip == se) {
+ if (cfs_rq->skip && cfs_rq->skip == se) {
struct sched_entity *second;
if (se == curr) {
@@ -4150,13 +4150,13 @@ pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
/*
* Prefer last buddy, try to return the CPU to a preempted task.
*/
- if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
+ if (left && cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
se = cfs_rq->last;
/*
* Someone really wants this to run. If it's not unfair, run it.
*/
- if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
+ if (left && cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
se = cfs_rq->next;
clear_buddies(cfs_rq, se);
@@ -6937,6 +6937,37 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_
set_last_buddy(se);
}
+static struct task_struct *
+pick_task_fair(struct rq *rq)
+{
+ struct cfs_rq *cfs_rq = &rq->cfs;
+ struct sched_entity *se;
+
+ if (!cfs_rq->nr_running)
+ return NULL;
+
+ do {
+ struct sched_entity *curr = cfs_rq->curr;
+
+ se = pick_next_entity(cfs_rq, NULL);
+
+ if (!(se || curr))
+ return NULL;
+
+ if (curr) {
+ if (se && curr->on_rq)
+ update_curr(cfs_rq);
+
+ if (!se || entity_before(curr, se))
+ se = curr;
+ }
+
+ cfs_rq = group_cfs_rq(se);
+ } while (cfs_rq);
+
+ return task_of(se);
+}
+
static struct task_struct *
pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
{
@@ -10648,6 +10679,8 @@ const struct sched_class fair_sched_class = {
.set_next_task = set_next_task_fair,
#ifdef CONFIG_SMP
+ .pick_task = pick_task_fair,
+
.select_task_rq = select_task_rq_fair,
.migrate_task_rq = migrate_task_rq_fair,
diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index 7ece8e820b5d..e7f38da60373 100644
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -373,6 +373,12 @@ static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p, int fl
resched_curr(rq);
}
+static struct task_struct *
+pick_task_idle(struct rq *rq)
+{
+ return rq->idle;
+}
+
static void put_prev_task_idle(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
{
}
@@ -386,11 +392,12 @@ static void set_next_task_idle(struct rq *rq, struct task_struct *next)
static struct task_struct *
pick_next_task_idle(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
{
- struct task_struct *next = rq->idle;
+ struct task_struct *next;
if (prev)
put_prev_task(rq, prev);
+ next = pick_task_idle(rq);
set_next_task_idle(rq, next);
return next;
@@ -458,6 +465,7 @@ const struct sched_class idle_sched_class = {
.set_next_task = set_next_task_idle,
#ifdef CONFIG_SMP
+ .pick_task = pick_task_idle,
.select_task_rq = select_task_rq_idle,
.set_cpus_allowed = set_cpus_allowed_common,
#endif
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 79f2e60516ef..81557224548c 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1548,20 +1548,29 @@ static struct task_struct *_pick_next_task_rt(struct rq *rq)
return rt_task_of(rt_se);
}
-static struct task_struct *
-pick_next_task_rt(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
+static struct task_struct *pick_task_rt(struct rq *rq)
{
struct task_struct *p;
struct rt_rq *rt_rq = &rq->rt;
- WARN_ON_ONCE(prev || rf);
-
if (!rt_rq->rt_queued)
return NULL;
p = _pick_next_task_rt(rq);
- set_next_task_rt(rq, p);
+ return p;
+}
+
+static struct task_struct *
+pick_next_task_rt(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
+{
+ struct task_struct *p;
+
+ WARN_ON_ONCE(prev || rf);
+
+ p = pick_task_rt(rq);
+ if (p)
+ set_next_task_rt(rq, p);
return p;
}
@@ -2364,6 +2373,8 @@ const struct sched_class rt_sched_class = {
.set_next_task = set_next_task_rt,
#ifdef CONFIG_SMP
+ .pick_task = pick_task_rt,
+
.select_task_rq = select_task_rq_rt,
.set_cpus_allowed = set_cpus_allowed_common,
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 460dd04e76af..a024dd80eeb3 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1682,6 +1682,8 @@ struct sched_class {
void (*set_next_task)(struct rq *rq, struct task_struct *p);
#ifdef CONFIG_SMP
+ struct task_struct * (*pick_task)(struct rq *rq);
+
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 new_cpu);
diff --git a/kernel/sched/stop_task.c b/kernel/sched/stop_task.c
index 7e1cee4e65b2..fb6c436cba6c 100644
--- a/kernel/sched/stop_task.c
+++ b/kernel/sched/stop_task.c
@@ -29,20 +29,30 @@ static void set_next_task_stop(struct rq *rq, struct task_struct *stop)
}
static struct task_struct *
-pick_next_task_stop(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
+pick_task_stop(struct rq *rq)
{
struct task_struct *stop = rq->stop;
- WARN_ON_ONCE(prev || rf);
-
if (!stop || !task_on_rq_queued(stop))
return NULL;
- set_next_task_stop(rq, stop);
-
return stop;
}
+static struct task_struct *
+pick_next_task_stop(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
+{
+ struct task_struct *p;
+
+ WARN_ON_ONCE(prev || rf);
+
+ p = pick_task_stop(rq);
+ if (p)
+ set_next_task_stop(rq, p);
+
+ return p;
+}
+
static void
enqueue_task_stop(struct rq *rq, struct task_struct *p, int flags)
{
@@ -129,6 +139,7 @@ const struct sched_class stop_sched_class = {
.set_next_task = set_next_task_stop,
#ifdef CONFIG_SMP
+ .pick_task = pick_task_stop,
.select_task_rq = select_task_rq_stop,
.set_cpus_allowed = set_cpus_allowed_common,
#endif
--
2.17.1
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