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Message-ID: <20250528080924.2273858-29-mingo@kernel.org>
Date: Wed, 28 May 2025 10:09:09 +0200
From: Ingo Molnar <mingo@...nel.org>
To: linux-kernel@...r.kernel.org
Cc: Dietmar Eggemann <dietmar.eggemann@....com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Peter Zijlstra <peterz@...radead.org>,
Shrikanth Hegde <sshegde@...ux.ibm.com>,
Thomas Gleixner <tglx@...utronix.de>,
Valentin Schneider <vschneid@...hat.com>,
Steven Rostedt <rostedt@...dmis.org>,
Mel Gorman <mgorman@...e.de>,
Vincent Guittot <vincent.guittot@...aro.org>,
Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
Ingo Molnar <mingo@...nel.org>,
Juri Lelli <juri.lelli@...hat.com>
Subject: [PATCH 28/43] sched/smp: Use the SMP version of the RT scheduling class
Simplify the scheduler by making formerly SMP-only primitives and data
structures unconditional in the RT policies scheduler.
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Cc: Dietmar Eggemann <dietmar.eggemann@....com>
Cc: Juri Lelli <juri.lelli@...hat.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Mel Gorman <mgorman@...e.de>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Shrikanth Hegde <sshegde@...ux.ibm.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Valentin Schneider <vschneid@...hat.com>
Cc: Vincent Guittot <vincent.guittot@...aro.org>
---
kernel/sched/rt.c | 72 ----------------------------------------------------
kernel/sched/sched.h | 2 --
2 files changed, 74 deletions(-)
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 0cd801458eef..7119f4c8aa68 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -75,12 +75,10 @@ void init_rt_rq(struct rt_rq *rt_rq)
/* delimiter for bitsearch: */
__set_bit(MAX_RT_PRIO, array->bitmap);
-#if defined CONFIG_SMP
rt_rq->highest_prio.curr = MAX_RT_PRIO-1;
rt_rq->highest_prio.next = MAX_RT_PRIO-1;
rt_rq->overloaded = 0;
plist_head_init(&rt_rq->pushable_tasks);
-#endif /* CONFIG_SMP */
/* We start is dequeued state, because no RT tasks are queued */
rt_rq->rt_queued = 0;
@@ -329,8 +327,6 @@ int alloc_rt_sched_group(struct task_group *tg, struct task_group *parent)
}
#endif /* !CONFIG_RT_GROUP_SCHED */
-#ifdef CONFIG_SMP
-
static inline bool need_pull_rt_task(struct rq *rq, struct task_struct *prev)
{
/* Try to pull RT tasks here if we lower this rq's prio */
@@ -430,21 +426,6 @@ static void dequeue_pushable_task(struct rq *rq, struct task_struct *p)
}
}
-#else /* !CONFIG_SMP: */
-
-static inline void enqueue_pushable_task(struct rq *rq, struct task_struct *p)
-{
-}
-
-static inline void dequeue_pushable_task(struct rq *rq, struct task_struct *p)
-{
-}
-
-static inline void rt_queue_push_tasks(struct rq *rq)
-{
-}
-#endif /* !CONFIG_SMP */
-
static void enqueue_top_rt_rq(struct rt_rq *rt_rq);
static void dequeue_top_rt_rq(struct rt_rq *rt_rq, unsigned int count);
@@ -594,17 +575,10 @@ static int rt_se_boosted(struct sched_rt_entity *rt_se)
return p->prio != p->normal_prio;
}
-#ifdef CONFIG_SMP
static inline const struct cpumask *sched_rt_period_mask(void)
{
return this_rq()->rd->span;
}
-#else
-static inline const struct cpumask *sched_rt_period_mask(void)
-{
- return cpu_online_mask;
-}
-#endif
static inline
struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
@@ -625,7 +599,6 @@ bool sched_rt_bandwidth_account(struct rt_rq *rt_rq)
rt_rq->rt_time < rt_b->rt_runtime);
}
-#ifdef CONFIG_SMP
/*
* We ran out of runtime, see if we can borrow some from our neighbours.
*/
@@ -798,9 +771,6 @@ static void balance_runtime(struct rt_rq *rt_rq)
raw_spin_lock(&rt_rq->rt_runtime_lock);
}
}
-#else /* !CONFIG_SMP: */
-static inline void balance_runtime(struct rt_rq *rt_rq) {}
-#endif /* !CONFIG_SMP */
static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun)
{
@@ -977,10 +947,8 @@ struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
return &cpu_rq(cpu)->rt;
}
-#ifdef CONFIG_SMP
static void __enable_runtime(struct rq *rq) { }
static void __disable_runtime(struct rq *rq) { }
-#endif
#endif /* !CONFIG_RT_GROUP_SCHED */
@@ -1075,8 +1043,6 @@ enqueue_top_rt_rq(struct rt_rq *rt_rq)
cpufreq_update_util(rq, 0);
}
-#if defined CONFIG_SMP
-
static void
inc_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio)
{
@@ -1107,16 +1073,6 @@ dec_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio)
cpupri_set(&rq->rd->cpupri, rq->cpu, rt_rq->highest_prio.curr);
}
-#else /* !CONFIG_SMP: */
-
-static inline
-void inc_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio) {}
-static inline
-void dec_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio) {}
-
-#endif /* !CONFIG_SMP */
-
-#if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
static void
inc_rt_prio(struct rt_rq *rt_rq, int prio)
{
@@ -1155,13 +1111,6 @@ dec_rt_prio(struct rt_rq *rt_rq, int prio)
dec_rt_prio_smp(rt_rq, prio, prev_prio);
}
-#else /* !(CONFIG_SMP || CONFIG_RT_GROUP_SCHED): */
-
-static inline void inc_rt_prio(struct rt_rq *rt_rq, int prio) {}
-static inline void dec_rt_prio(struct rt_rq *rt_rq, int prio) {}
-
-#endif /* !(CONFIG_SMP || CONFIG_RT_GROUP_SCHED) */
-
#ifdef CONFIG_RT_GROUP_SCHED
static void
@@ -1538,7 +1487,6 @@ static void yield_task_rt(struct rq *rq)
requeue_task_rt(rq, rq->curr, 0);
}
-#ifdef CONFIG_SMP
static int find_lowest_rq(struct task_struct *task);
static int
@@ -1653,7 +1601,6 @@ static int balance_rt(struct rq *rq, struct task_struct *p, struct rq_flags *rf)
return sched_stop_runnable(rq) || sched_dl_runnable(rq) || sched_rt_runnable(rq);
}
-#endif /* CONFIG_SMP */
/*
* Preempt the current task with a newly woken task if needed:
@@ -1667,7 +1614,6 @@ static void wakeup_preempt_rt(struct rq *rq, struct task_struct *p, int flags)
return;
}
-#ifdef CONFIG_SMP
/*
* If:
*
@@ -1682,7 +1628,6 @@ static void wakeup_preempt_rt(struct rq *rq, struct task_struct *p, int flags)
*/
if (p->prio == donor->prio && !test_tsk_need_resched(rq->curr))
check_preempt_equal_prio(rq, p);
-#endif /* CONFIG_SMP */
}
static inline void set_next_task_rt(struct rq *rq, struct task_struct *p, bool first)
@@ -1776,8 +1721,6 @@ static void put_prev_task_rt(struct rq *rq, struct task_struct *p, struct task_s
enqueue_pushable_task(rq, p);
}
-#ifdef CONFIG_SMP
-
/* Only try algorithms three times */
#define RT_MAX_TRIES 3
@@ -2451,11 +2394,6 @@ void __init init_sched_rt_class(void)
GFP_KERNEL, cpu_to_node(i));
}
}
-#else /* !CONFIG_SMP: */
-void __init init_sched_rt_class(void)
-{
-}
-#endif /* !CONFIG_SMP */
/*
* When switching a task to RT, we may overload the runqueue
@@ -2479,10 +2417,8 @@ static void switched_to_rt(struct rq *rq, struct task_struct *p)
* then see if we can move to another run queue.
*/
if (task_on_rq_queued(p)) {
-#ifdef CONFIG_SMP
if (p->nr_cpus_allowed > 1 && rq->rt.overloaded)
rt_queue_push_tasks(rq);
-#endif /* CONFIG_SMP */
if (p->prio < rq->donor->prio && cpu_online(cpu_of(rq)))
resched_curr(rq);
}
@@ -2499,7 +2435,6 @@ prio_changed_rt(struct rq *rq, struct task_struct *p, int oldprio)
return;
if (task_current_donor(rq, p)) {
-#ifdef CONFIG_SMP
/*
* If our priority decreases while running, we
* may need to pull tasks to this runqueue.
@@ -2513,11 +2448,6 @@ prio_changed_rt(struct rq *rq, struct task_struct *p, int oldprio)
*/
if (p->prio > rq->rt.highest_prio.curr)
resched_curr(rq);
-#else /* !CONFIG_SMP: */
- /* For UP simply resched on drop of prio */
- if (oldprio < p->prio)
- resched_curr(rq);
-#endif /* !CONFIG_SMP */
} else {
/*
* This task is not running, but if it is
@@ -2638,7 +2568,6 @@ DEFINE_SCHED_CLASS(rt) = {
.put_prev_task = put_prev_task_rt,
.set_next_task = set_next_task_rt,
-#ifdef CONFIG_SMP
.balance = balance_rt,
.select_task_rq = select_task_rq_rt,
.set_cpus_allowed = set_cpus_allowed_common,
@@ -2647,7 +2576,6 @@ DEFINE_SCHED_CLASS(rt) = {
.task_woken = task_woken_rt,
.switched_from = switched_from_rt,
.find_lock_rq = find_lock_lowest_rq,
-#endif /* !CONFIG_SMP */
.task_tick = task_tick_rt,
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index de130ffa42b2..7c67e1ccc0ae 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -791,11 +791,9 @@ struct rt_rq {
int curr; /* highest queued rt task prio */
int next; /* next highest */
} highest_prio;
-#ifdef CONFIG_SMP
bool overloaded;
struct plist_head pushable_tasks;
-#endif /* CONFIG_SMP */
int rt_queued;
#ifdef CONFIG_RT_GROUP_SCHED
--
2.45.2
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