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From 7e826e336f66907d688e4c457f2104618d960de3 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@infradead.org>
Date: Fri, 23 Oct 2020 12:12:05 +0200
Subject: [PATCH 008/296] sched: Fix hotplug vs CPU bandwidth control
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.35-rt39.tar.xz
Since we now migrate tasks away before DYING, we should also move
bandwidth unthrottle, otherwise we can gain tasks from unthrottle
after we expect all tasks to be gone already.
Also; it looks like the RT balancers don't respect cpu_active() and
instead rely on rq->online in part, complete this. This too requires
we do set_rq_offline() earlier to match the cpu_active() semantics.
(The bigger patch is to convert RT to cpu_active() entirely)
Since set_rq_online() is called from sched_cpu_activate(), place
set_rq_offline() in sched_cpu_deactivate().
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
kernel/sched/core.c | 14 ++++++++++----
kernel/sched/deadline.c | 2 +-
kernel/sched/rt.c | 2 +-
3 files changed, 12 insertions(+), 6 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 9ad43e648a78..f7403832b3b1 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6975,6 +6975,8 @@ int sched_cpu_activate(unsigned int cpu)
int sched_cpu_deactivate(unsigned int cpu)
{
+ struct rq *rq = cpu_rq(cpu);
+ struct rq_flags rf;
int ret;
set_cpu_active(cpu, false);
@@ -6989,6 +6991,14 @@ int sched_cpu_deactivate(unsigned int cpu)
balance_push_set(cpu, true);
+ rq_lock_irqsave(rq, &rf);
+ if (rq->rd) {
+ update_rq_clock(rq);
+ BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
+ set_rq_offline(rq);
+ }
+ rq_unlock_irqrestore(rq, &rf);
+
#ifdef CONFIG_SCHED_SMT
/*
* When going down, decrement the number of cores with SMT present.
@@ -7070,10 +7080,6 @@ int sched_cpu_dying(unsigned int cpu)
sched_tick_stop(cpu);
rq_lock_irqsave(rq, &rf);
- if (rq->rd) {
- BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
- set_rq_offline(rq);
- }
BUG_ON(rq->nr_running != 1);
rq_unlock_irqrestore(rq, &rf);
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 8d06d1f4e2f7..e0564abfece1 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -565,7 +565,7 @@ static int push_dl_task(struct rq *rq);
static inline bool need_pull_dl_task(struct rq *rq, struct task_struct *prev)
{
- return dl_task(prev);
+ return rq->online && dl_task(prev);
}
static DEFINE_PER_CPU(struct callback_head, dl_push_head);
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 49ec096a8aa1..40a46639f78a 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -265,7 +265,7 @@ static void pull_rt_task(struct rq *this_rq);
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 */
- return rq->rt.highest_prio.curr > prev->prio;
+ return rq->online && rq->rt.highest_prio.curr > prev->prio;
}
static inline int rt_overloaded(struct rq *rq)
--
2.30.2
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