linux-kernel - [GIT PULL] scheduler fixes

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Date:   Mon, 30 Jul 2018 19:56:35 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: [GIT PULL] scheduler fixes

Linus,

Please pull the latest sched-urgent-for-linus git tree from:

   git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git sched-urgent-for-linus

   # HEAD: f3d133ee0a17d5694c6f21873eec9863e11fa423 sched/rt: Restore rt_runtime after disabling RT_RUNTIME_SHARE

Misc fixes:

 - a deadline scheduler related bug fix which triggered a kernel warning
 - an RT_RUNTIME_SHARE fix
 - a stop_machine preemption fix
 - a potential NULL dereference fix in sched_domain_debug_one()

 Thanks,

	Ingo

------------------>
Daniel Bristot de Oliveira (1):
      sched/deadline: Update rq_clock of later_rq when pushing a task

Hailong Liu (1):
      sched/rt: Restore rt_runtime after disabling RT_RUNTIME_SHARE

Isaac J. Manjarres (1):
      stop_machine: Disable preemption after queueing stopper threads

Yi Wang (1):
      sched/topology: Check variable group before dereferencing it


 kernel/sched/deadline.c |  8 +++++++-
 kernel/sched/rt.c       |  2 ++
 kernel/sched/topology.c |  2 +-
 kernel/stop_machine.c   | 10 +++++++++-
 4 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 10c7b51c0d1f..b5fbdde6afa9 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -2090,8 +2090,14 @@ static int push_dl_task(struct rq *rq)
 	sub_rq_bw(&next_task->dl, &rq->dl);
 	set_task_cpu(next_task, later_rq->cpu);
 	add_rq_bw(&next_task->dl, &later_rq->dl);
+
+	/*
+	 * Update the later_rq clock here, because the clock is used
+	 * by the cpufreq_update_util() inside __add_running_bw().
+	 */
+	update_rq_clock(later_rq);
 	add_running_bw(&next_task->dl, &later_rq->dl);
-	activate_task(later_rq, next_task, 0);
+	activate_task(later_rq, next_task, ENQUEUE_NOCLOCK);
 	ret = 1;
 
 	resched_curr(later_rq);
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 572567078b60..eaaec8364f96 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -836,6 +836,8 @@ static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun)
 		 * can be time-consuming. Try to avoid it when possible.
 		 */
 		raw_spin_lock(&rt_rq->rt_runtime_lock);
+		if (!sched_feat(RT_RUNTIME_SHARE) && rt_rq->rt_runtime != RUNTIME_INF)
+			rt_rq->rt_runtime = rt_b->rt_runtime;
 		skip = !rt_rq->rt_time && !rt_rq->rt_nr_running;
 		raw_spin_unlock(&rt_rq->rt_runtime_lock);
 		if (skip)
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 05a831427bc7..56a0fed30c0a 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -47,7 +47,7 @@ static int sched_domain_debug_one(struct sched_domain *sd, int cpu, int level,
 	if (!cpumask_test_cpu(cpu, sched_domain_span(sd))) {
 		printk(KERN_ERR "ERROR: domain->span does not contain CPU%d\n", cpu);
 	}
-	if (!cpumask_test_cpu(cpu, sched_group_span(group))) {
+	if (group && !cpumask_test_cpu(cpu, sched_group_span(group))) {
 		printk(KERN_ERR "ERROR: domain->groups does not contain CPU%d\n", cpu);
 	}
 
diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index 1ff523dae6e2..e190d1ef3a23 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -260,6 +260,15 @@ static int cpu_stop_queue_two_works(int cpu1, struct cpu_stop_work *work1,
 	err = 0;
 	__cpu_stop_queue_work(stopper1, work1, &wakeq);
 	__cpu_stop_queue_work(stopper2, work2, &wakeq);
+	/*
+	 * The waking up of stopper threads has to happen
+	 * in the same scheduling context as the queueing.
+	 * Otherwise, there is a possibility of one of the
+	 * above stoppers being woken up by another CPU,
+	 * and preempting us. This will cause us to n ot
+	 * wake up the other stopper forever.
+	 */
+	preempt_disable();
 unlock:
 	raw_spin_unlock(&stopper2->lock);
 	raw_spin_unlock_irq(&stopper1->lock);
@@ -271,7 +280,6 @@ static int cpu_stop_queue_two_works(int cpu1, struct cpu_stop_work *work1,
 	}
 
 	if (!err) {
-		preempt_disable();
 		wake_up_q(&wakeq);
 		preempt_enable();
 	}