From: Vineeth Remanan Pillai <vpillai@digitalocean.com>
To: Nishanth Aravamudan <naravamudan@digitalocean.com>,
Julien Desfossez <jdesfossez@digitalocean.com>,
Peter Zijlstra <peterz@infradead.org>,
Tim Chen <tim.c.chen@linux.intel.com>,
mingo@kernel.org, tglx@linutronix.de, pjt@google.com,
torvalds@linux-foundation.org
Cc: linux-kernel@vger.kernel.org, subhra.mazumdar@oracle.com,
fweisbec@gmail.com, keescook@chromium.org, kerrnel@google.com,
Phil Auld <pauld@redhat.com>, Aaron Lu <aaron.lwe@gmail.com>,
Aubrey Li <aubrey.intel@gmail.com>,
Valentin Schneider <valentin.schneider@arm.com>,
Mel Gorman <mgorman@techsingularity.net>,
Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Vineeth Remanan Pillai <vpillai@digitalocean.com>
Subject: [RFC PATCH v2 09/17] sched: Introduce sched_class::pick_task()
Date: Tue, 23 Apr 2019 16:18:14 +0000 [thread overview]
Message-ID: <e2f1d30b0b3bb62c01824f422badf159147982d7.1556025155.git.vpillai@digitalocean.com> (raw)
In-Reply-To: <cover.1556025155.git.vpillai@digitalocean.com>
In-Reply-To: <cover.1556025155.git.vpillai@digitalocean.com>
From: "Peter Zijlstra (Intel)" <peterz@infradead.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@infradead.org>
Signed-off-by: Vineeth Remanan Pillai <vpillai@digitalocean.com>
Signed-off-by: Julien Desfossez <jdesfossez@digitalocean.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
next prev parent reply other threads:[~2019-04-23 16:18 UTC|newest]
Thread overview: 109+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-23 16:18 [RFC PATCH v2 00/17] Core scheduling v2 Vineeth Remanan Pillai
2019-04-23 16:18 ` [RFC PATCH v2 01/17] stop_machine: Fix stop_cpus_in_progress ordering Vineeth Remanan Pillai
2019-04-23 16:18 ` [RFC PATCH v2 02/17] sched: Fix kerneldoc comment for ia64_set_curr_task Vineeth Remanan Pillai
2019-04-23 16:18 ` [RFC PATCH v2 03/17] sched: Wrap rq::lock access Vineeth Remanan Pillai
2019-04-23 16:18 ` [RFC PATCH v2 04/17] sched/{rt,deadline}: Fix set_next_task vs pick_next_task Vineeth Remanan Pillai
2019-04-23 16:18 ` [RFC PATCH v2 05/17] sched: Add task_struct pointer to sched_class::set_curr_task Vineeth Remanan Pillai
2019-04-23 16:18 ` [RFC PATCH v2 06/17] sched/fair: Export newidle_balance() Vineeth Remanan Pillai
2019-04-23 16:18 ` [RFC PATCH v2 07/17] sched: Allow put_prev_task() to drop rq->lock Vineeth Remanan Pillai
2019-04-23 16:18 ` [RFC PATCH v2 08/17] sched: Rework pick_next_task() slow-path Vineeth Remanan Pillai
2019-04-23 16:18 ` Vineeth Remanan Pillai [this message]
2019-04-26 14:02 ` [RFC PATCH v2 09/17] sched: Introduce sched_class::pick_task() Peter Zijlstra
2019-04-26 16:10 ` Vineeth Remanan Pillai
2019-04-29 5:38 ` Aaron Lu
2019-04-23 16:18 ` [RFC PATCH v2 10/17] sched: Core-wide rq->lock Vineeth Remanan Pillai
2019-04-23 16:18 ` [RFC PATCH v2 11/17] sched: Basic tracking of matching tasks Vineeth Remanan Pillai
2019-04-24 0:08 ` Tim Chen
2019-04-24 20:43 ` Vineeth Remanan Pillai
2019-04-24 22:12 ` Tim Chen
2019-04-25 14:35 ` Phil Auld
2019-05-22 19:52 ` Vineeth Remanan Pillai
2019-04-24 0:17 ` Tim Chen
2019-04-24 20:43 ` Vineeth Remanan Pillai
2019-04-29 3:36 ` Aaron Lu
2019-05-10 13:06 ` Peter Zijlstra
2019-04-29 6:15 ` Aaron Lu
2019-05-01 23:27 ` Tim Chen
2019-05-03 0:06 ` Tim Chen
2019-05-08 15:49 ` Aubrey Li
2019-05-08 18:19 ` Subhra Mazumdar
2019-05-08 18:37 ` Subhra Mazumdar
2019-05-09 0:01 ` Aubrey Li
2019-05-09 0:25 ` Subhra Mazumdar
2019-05-09 1:38 ` Aubrey Li
2019-05-09 2:14 ` Subhra Mazumdar
2019-05-09 15:10 ` Aubrey Li
2019-05-09 17:50 ` Subhra Mazumdar
2019-05-10 0:09 ` Tim Chen
2019-04-23 16:18 ` [RFC PATCH v2 12/17] sched: A quick and dirty cgroup tagging interface Vineeth Remanan Pillai
2019-04-25 14:26 ` Phil Auld
2019-04-26 14:13 ` Peter Zijlstra
2019-04-26 14:19 ` Phil Auld
2019-05-10 15:12 ` Julien Desfossez
2019-04-23 16:18 ` [RFC PATCH v2 13/17] sched: Add core wide task selection and scheduling Vineeth Remanan Pillai
2019-04-29 7:13 ` Aaron Lu
2019-05-18 15:37 ` Aubrey Li
2019-05-20 13:04 ` Phil Auld
2019-05-20 14:04 ` Vineeth Pillai
2019-05-21 8:19 ` Aubrey Li
2019-05-21 13:24 ` Vineeth Pillai
2019-04-23 16:18 ` [RFC PATCH v2 14/17] sched/fair: Add a few assertions Vineeth Remanan Pillai
2019-04-23 16:18 ` [RFC PATCH v2 15/17] sched: Trivial forced-newidle balancer Vineeth Remanan Pillai
2019-04-23 23:46 ` Aubrey Li
2019-04-24 14:03 ` Vineeth Remanan Pillai
2019-04-24 14:05 ` Vineeth Remanan Pillai
2019-04-23 16:18 ` [RFC PATCH v2 16/17] sched: Wake up sibling if it has something to run Vineeth Remanan Pillai
2019-04-26 15:03 ` Peter Zijlstra
2019-04-29 12:36 ` Julien Desfossez
2019-04-23 16:18 ` [RFC PATCH v2 17/17] sched: Debug bits Vineeth Remanan Pillai
2019-05-17 17:18 ` Aubrey Li
2019-04-23 18:02 ` [RFC PATCH v2 00/17] Core scheduling v2 Phil Auld
2019-04-23 18:45 ` Vineeth Remanan Pillai
2019-04-29 3:53 ` Aaron Lu
2019-05-06 19:39 ` Julien Desfossez
2019-05-08 2:30 ` Aaron Lu
2019-05-08 17:49 ` Julien Desfossez
2019-05-09 2:11 ` Aaron Lu
2019-05-15 21:36 ` Vineeth Remanan Pillai
2019-04-23 23:25 ` Aubrey Li
2019-04-24 11:19 ` Vineeth Remanan Pillai
2019-05-15 21:39 ` Vineeth Remanan Pillai
2019-04-24 13:13 ` Aubrey Li
2019-04-24 14:00 ` Julien Desfossez
2019-04-25 3:15 ` Aubrey Li
2019-04-25 9:55 ` Ingo Molnar
2019-04-25 14:46 ` Mel Gorman
2019-04-25 18:53 ` Ingo Molnar
2019-04-25 18:59 ` Thomas Gleixner
2019-04-25 19:34 ` Ingo Molnar
2019-04-25 21:31 ` Mel Gorman
2019-04-26 8:42 ` Ingo Molnar
2019-04-26 10:43 ` Mel Gorman
2019-04-26 18:37 ` Subhra Mazumdar
2019-04-26 19:49 ` Mel Gorman
2019-04-26 9:45 ` Ingo Molnar
2019-04-26 10:19 ` Mel Gorman
2019-04-27 9:06 ` Ingo Molnar
2019-04-26 9:51 ` Ingo Molnar
2019-04-26 14:15 ` Phil Auld
2019-04-26 2:18 ` Aubrey Li
2019-04-26 9:51 ` Ingo Molnar
2019-04-27 3:51 ` Aubrey Li
2019-04-27 9:17 ` Ingo Molnar
2019-04-27 14:04 ` Aubrey Li
2019-04-27 14:21 ` Ingo Molnar
2019-04-27 15:54 ` Aubrey Li
2019-04-28 9:33 ` Ingo Molnar
2019-04-28 10:29 ` Aubrey Li
2019-04-28 12:17 ` Ingo Molnar
2019-04-29 2:17 ` Li, Aubrey
2019-04-29 6:14 ` Ingo Molnar
2019-04-29 13:25 ` Li, Aubrey
2019-04-29 15:39 ` Phil Auld
2019-04-30 1:24 ` Aubrey Li
2019-04-29 16:00 ` Ingo Molnar
2019-04-30 1:34 ` Aubrey Li
2019-04-30 4:42 ` Ingo Molnar
2019-05-18 0:58 ` Li, Aubrey
2019-05-18 1:08 ` Li, Aubrey
2019-04-25 14:36 ` Julien Desfossez
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