Commit 21f56ffe authored by Peter Zijlstra's avatar Peter Zijlstra

sched: Introduce sched_class::pick_task()

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: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
[Vineeth: folded fixes]
Signed-off-by: default avatarVineeth Remanan Pillai <viremana@linux.microsoft.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: default avatarDon Hiatt <dhiatt@digitalocean.com>
Tested-by: default avatarHongyu Ning <hongyu.ning@linux.intel.com>
Tested-by: default avatarVincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20210422123308.437092775@infradead.org
parent 875feb41
......@@ -1852,7 +1852,7 @@ 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;
......@@ -1864,7 +1864,18 @@ 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;
}
......@@ -2539,6 +2550,7 @@ DEFINE_SCHED_CLASS(dl) = {
#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,
......
......@@ -4419,6 +4419,8 @@ check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
static void
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
clear_buddies(cfs_rq, se);
/* 'current' is not kept within the tree. */
if (se->on_rq) {
/*
......@@ -4478,7 +4480,7 @@ 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) {
......@@ -4505,8 +4507,6 @@ pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
se = cfs_rq->last;
}
clear_buddies(cfs_rq, se);
return se;
}
......@@ -7095,6 +7095,39 @@ 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 sched_entity *se;
struct cfs_rq *cfs_rq;
again:
cfs_rq = &rq->cfs;
if (!cfs_rq->nr_running)
return NULL;
do {
struct sched_entity *curr = cfs_rq->curr;
/* When we pick for a remote RQ, we'll not have done put_prev_entity() */
if (curr) {
if (curr->on_rq)
update_curr(cfs_rq);
else
curr = NULL;
if (unlikely(check_cfs_rq_runtime(cfs_rq)))
goto again;
}
se = pick_next_entity(cfs_rq, 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)
{
......@@ -11298,6 +11331,7 @@ DEFINE_SCHED_CLASS(fair) = {
#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,
......
......@@ -439,6 +439,13 @@ 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;
......@@ -506,6 +513,7 @@ DEFINE_SCHED_CLASS(idle) = {
#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
......
......@@ -1626,7 +1626,7 @@ 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;
......@@ -1634,7 +1634,17 @@ 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;
}
......@@ -2483,6 +2493,7 @@ DEFINE_SCHED_CLASS(rt) = {
#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,
......
......@@ -1953,6 +1953,9 @@ struct sched_class {
#ifdef CONFIG_SMP
int (*balance)(struct rq *rq, struct task_struct *prev, struct rq_flags *rf);
int (*select_task_rq)(struct task_struct *p, int task_cpu, int flags);
struct task_struct * (*pick_task)(struct rq *rq);
void (*migrate_task_rq)(struct task_struct *p, int new_cpu);
void (*task_woken)(struct rq *this_rq, struct task_struct *task);
......
......@@ -34,15 +34,24 @@ 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)
{
......@@ -123,6 +132,7 @@ DEFINE_SCHED_CLASS(stop) = {
#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
......
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