From: Peter Zijlstra <pet...@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.
Tested-by: Julien Desfossez <jdesfos...@digitalocean.com>
Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
Signed-off-by: Vineeth Remanan Pillai <vpil...@digitalocean.com>
Signed-off-by: Julien Desfossez <jdesfos...@digitalocean.com>
Signed-off-by: Joel Fernandes (Google) <j...@joelfernandes.org>
---
kernel/sched/deadline.c | 16 ++++++++++++++--
kernel/sched/fair.c | 32 +++++++++++++++++++++++++++++++-
kernel/sched/idle.c | 8 ++++++++
kernel/sched/rt.c | 14 ++++++++++++--
kernel/sched/sched.h | 3 +++
kernel/sched/stop_task.c | 13 +++++++++++--
6 files changed, 79 insertions(+), 7 deletions(-)
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 814ec49502b1..0271a7848ab3 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1848,7 +1848,7 @@ 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)
+static struct task_struct *pick_task_dl(struct rq *rq)
{
struct sched_dl_entity *dl_se;
struct dl_rq *dl_rq = &rq->dl;
@@ -1860,7 +1860,18 @@ 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, true);
+
+ return p;
+}
+
+static struct task_struct *pick_next_task_dl(struct rq *rq)
+{
+ struct task_struct *p;
+
+ p = pick_task_dl(rq);
+ if (p)
+ set_next_task_dl(rq, p, true);
+
return p;
}
@@ -2517,6 +2528,7 @@ const struct sched_class dl_sched_class
#ifdef CONFIG_SMP
.balance = balance_dl,
+ .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 dbd9368a959d..bd6aed63f5e3 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4450,7 +4450,7 @@ 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) {
@@ -6976,6 +6976,35 @@ static void check_preempt_wakeup(struct rq *rq, struct
task_struct *p, int wake_
set_last_buddy(se);
}
+#ifdef CONFIG_SMP
+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 (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);
+}
+#endif
+
struct task_struct *
pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct rq_flags
*rf)
{
@@ -11173,6 +11202,7 @@ const struct sched_class fair_sched_class
#ifdef CONFIG_SMP
.balance = balance_fair,
+ .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 8ce6e80352cf..ce7552c6bc65 100644
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -405,6 +405,13 @@ static void set_next_task_idle(struct rq *rq, struct
task_struct *next, bool fir
schedstat_inc(rq->sched_goidle);
}
+#ifdef CONFIG_SMP
+static struct task_struct *pick_task_idle(struct rq *rq)
+{
+ return rq->idle;
+}
+#endif
+
struct task_struct *pick_next_task_idle(struct rq *rq)
{
struct task_struct *next = rq->idle;
@@ -472,6 +479,7 @@ const struct sched_class idle_sched_class
#ifdef CONFIG_SMP
.balance = balance_idle,
+ .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 e57fca05b660..a5851c775270 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1624,7 +1624,7 @@ 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)
+static struct task_struct *pick_task_rt(struct rq *rq)
{
struct task_struct *p;
@@ -1632,7 +1632,16 @@ 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, true);
+
+ return p;
+}
+
+static struct task_struct *pick_next_task_rt(struct rq *rq)
+{
+ struct task_struct *p = pick_task_rt(rq);
+ if (p)
+ set_next_task_rt(rq, p, true);
+
return p;
}
@@ -2443,6 +2452,7 @@ const struct sched_class rt_sched_class
#ifdef CONFIG_SMP
.balance = balance_rt,
+ .pick_task = pick_task_rt,
.select_task_rq = select_task_rq_rt,
.set_cpus_allowed = set_cpus_allowed_common,
.rq_online = rq_online_rt,
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 587ebabebaff..54bfac702805 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1800,6 +1800,9 @@ struct sched_class {
#ifdef CONFIG_SMP
int (*balance)(struct rq *rq, struct task_struct *prev, struct rq_flags
*rf);
+
+ 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 394bc8126a1e..8f92915dd95e 100644
--- a/kernel/sched/stop_task.c
+++ b/kernel/sched/stop_task.c
@@ -34,15 +34,23 @@ static void set_next_task_stop(struct rq *rq, struct
task_struct *stop, bool fir
stop->se.exec_start = rq_clock_task(rq);
}
-static struct task_struct *pick_next_task_stop(struct rq *rq)
+static struct task_struct *pick_task_stop(struct rq *rq)
{
if (!sched_stop_runnable(rq))
return NULL;
- set_next_task_stop(rq, rq->stop, true);
return rq->stop;
}
+static struct task_struct *pick_next_task_stop(struct rq *rq)
+{
+ struct task_struct *p = pick_task_stop(rq);
+ if (p)
+ set_next_task_stop(rq, p, true);
+
+ return p;
+}
+
static void
enqueue_task_stop(struct rq *rq, struct task_struct *p, int flags)
{
@@ -124,6 +132,7 @@ const struct sched_class stop_sched_class
#ifdef CONFIG_SMP
.balance = balance_stop,
+ .pick_task = pick_task_stop,
.select_task_rq = select_task_rq_stop,
.set_cpus_allowed = set_cpus_allowed_common,
#endif
--
2.29.0.rc1.297.gfa9743e501-goog
