linux-kernel - [GIT PULL] scheduler fixes

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Date:   Fri, 15 Dec 2017 16:35:28 +0100
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: f73c52a5bcd1710994e53fbccc378c42b97a06b6 sched/rt: Do not pull from current CPU if only one CPU to pull

Two fixes: a crash fix for an ARM SoC platform, and kernel-doc warnings fixes.

 Thanks,

	Ingo

------------------>
Randy Dunlap (1):
      sched/core: Fix kernel-doc warnings after code movement

Steven Rostedt (1):
      sched/rt: Do not pull from current CPU if only one CPU to pull


 kernel/sched/core.c | 22 +++++++++++-----------
 kernel/sched/rt.c   |  8 +++++++-
 2 files changed, 18 insertions(+), 12 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 75554f366fd3..644fa2e3d993 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5097,17 +5097,6 @@ SYSCALL_DEFINE1(sched_get_priority_min, int, policy)
 	return ret;
 }
 
-/**
- * sys_sched_rr_get_interval - return the default timeslice of a process.
- * @pid: pid of the process.
- * @interval: userspace pointer to the timeslice value.
- *
- * this syscall writes the default timeslice value of a given process
- * into the user-space timespec buffer. A value of '0' means infinity.
- *
- * Return: On success, 0 and the timeslice is in @interval. Otherwise,
- * an error code.
- */
 static int sched_rr_get_interval(pid_t pid, struct timespec64 *t)
 {
 	struct task_struct *p;
@@ -5144,6 +5133,17 @@ static int sched_rr_get_interval(pid_t pid, struct timespec64 *t)
 	return retval;
 }
 
+/**
+ * sys_sched_rr_get_interval - return the default timeslice of a process.
+ * @pid: pid of the process.
+ * @interval: userspace pointer to the timeslice value.
+ *
+ * this syscall writes the default timeslice value of a given process
+ * into the user-space timespec buffer. A value of '0' means infinity.
+ *
+ * Return: On success, 0 and the timeslice is in @interval. Otherwise,
+ * an error code.
+ */
 SYSCALL_DEFINE2(sched_rr_get_interval, pid_t, pid,
 		struct timespec __user *, interval)
 {
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 4056c19ca3f0..665ace2fc558 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -2034,8 +2034,9 @@ static void pull_rt_task(struct rq *this_rq)
 	bool resched = false;
 	struct task_struct *p;
 	struct rq *src_rq;
+	int rt_overload_count = rt_overloaded(this_rq);
 
-	if (likely(!rt_overloaded(this_rq)))
+	if (likely(!rt_overload_count))
 		return;
 
 	/*
@@ -2044,6 +2045,11 @@ static void pull_rt_task(struct rq *this_rq)
 	 */
 	smp_rmb();
 
+	/* If we are the only overloaded CPU do nothing */
+	if (rt_overload_count == 1 &&
+	    cpumask_test_cpu(this_rq->cpu, this_rq->rd->rto_mask))
+		return;
+
 #ifdef HAVE_RT_PUSH_IPI
 	if (sched_feat(RT_PUSH_IPI)) {
 		tell_cpu_to_push(this_rq);