Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler updates from Ingo Molnar:

 - Move the nohz kick code out of the scheduler tick to a dedicated IPI,
   from Frederic Weisbecker.

  This necessiated quite some background infrastructure rework,
  including:

   * Clean up some irq-work internals
   * Implement remote irq-work
   * Implement nohz kick on top of remote irq-work
   * Move full dynticks timer enqueue notification to new kick
   * Move multi-task notification to new kick
   * Remove unecessary barriers on multi-task notification

 - Remove proliferation of wait_on_bit() action functions and allow
   wait_on_bit_action() functions to support a timeout.  (Neil Brown)

 - Another round of sched/numa improvements, cleanups and fixes.  (Rik
   van Riel)

 - Implement fast idling of CPUs when the system is partially loaded,
   for better scalability.  (Tim Chen)

 - Restructure and fix the CPU hotplug handling code that may leave
   cfs_rq and rt_rq's throttled when tasks are migrated away from a dead
   cpu.  (Kirill Tkhai)

 - Robustify the sched topology setup code.  (Peterz Zijlstra)

 - Improve sched_feat() handling wrt.  static_keys (Jason Baron)

 - Misc fixes.

* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (37 commits)
  sched/fair: Fix 'make xmldocs' warning caused by missing description
  sched: Use macro for magic number of -1 for setparam
  sched: Robustify topology setup
  sched: Fix sched_setparam() policy == -1 logic
  sched: Allow wait_on_bit_action() functions to support a timeout
  sched: Remove proliferation of wait_on_bit() action functions
  sched/numa: Revert "Use effective_load() to balance NUMA loads"
  sched: Fix static_key race with sched_feat()
  sched: Remove extra static_key*() function indirection
  sched/rt: Fix replenish_dl_entity() comments to match the current upstream code
  sched: Transform resched_task() into resched_curr()
  sched/deadline: Kill task_struct->pi_top_task
  sched: Rework check_for_tasks()
  sched/rt: Enqueue just unthrottled rt_rq back on the stack in __disable_runtime()
  sched/fair: Disable runtime_enabled on dying rq
  sched/numa: Change scan period code to match intent
  sched/numa: Rework best node setting in task_numa_migrate()
  sched/numa: Examine a task move when examining a task swap
  sched/numa: Simplify task_numa_compare()
  sched/numa: Use effective_load() to balance NUMA loads
  ...

1 files changed, 20 insertions, 13 deletions

diff --git a/kernel/cpu.c b/kernel/cpu.c
index a343bde710b1..81e2a388a0f6 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -274,21 +274,28 @@ void clear_tasks_mm_cpumask(int cpu)
 	rcu_read_unlock();
 }
 
-static inline void check_for_tasks(int cpu)
+static inline void check_for_tasks(int dead_cpu)
 {
-	struct task_struct *p;
-	cputime_t utime, stime;
+	struct task_struct *g, *p;
 
-	write_lock_irq(&tasklist_lock);
-	for_each_process(p) {
-		task_cputime(p, &utime, &stime);
-		if (task_cpu(p) == cpu && p->state == TASK_RUNNING &&
-		    (utime || stime))
-			pr_warn("Task %s (pid = %d) is on cpu %d (state = %ld, flags = %x)\n",
-				p->comm, task_pid_nr(p), cpu,
-				p->state, p->flags);
-	}
-	write_unlock_irq(&tasklist_lock);
+	read_lock_irq(&tasklist_lock);
+	do_each_thread(g, p) {
+		if (!p->on_rq)
+			continue;
+		/*
+		 * We do the check with unlocked task_rq(p)->lock.
+		 * Order the reading to do not warn about a task,
+		 * which was running on this cpu in the past, and
+		 * it's just been woken on another cpu.
+		 */
+		rmb();
+		if (task_cpu(p) != dead_cpu)
+			continue;
+
+		pr_warn("Task %s (pid=%d) is on cpu %d (state=%ld, flags=%x)\n",
+			p->comm, task_pid_nr(p), dead_cpu, p->state, p->flags);
+	} while_each_thread(g, p);
+	read_unlock_irq(&tasklist_lock);
 }
 
 struct take_cpu_down_param {