Merge branch 'for-5.1/nfit/ars' into libnvdimm-for-next

Merge several updates to the ARS implementation. Highlights include:

* Support retrieval of short-ARS results if the ARS state is "requires
  continuation", and even if the "no_init_ars" module parameter is
  specified.
* Allow busy-polling of the kernel ARS state by allowing root to reset
  the exponential back-off timer.
* Filter potentially stale ARS results by tracking query-ARS relative to
  the previous start-ARS.

1 files changed, 17 insertions, 4 deletions

diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index fe24de3fbc93..c3484785b179 100644
--- a/kernel/sched/psi.c
+++ b/kernel/sched/psi.c
@@ -124,6 +124,7 @@
  * sampling of the aggregate task states would be.
  */
 
+#include "../workqueue_internal.h"
 #include <linux/sched/loadavg.h>
 #include <linux/seq_file.h>
 #include <linux/proc_fs.h>
@@ -480,9 +481,6 @@ static void psi_group_change(struct psi_group *group, int cpu,
                         groupc->tasks[t]++;
 
         write_seqcount_end(&groupc->seq);
-
-        if (!delayed_work_pending(&group->clock_work))
-                schedule_delayed_work(&group->clock_work, PSI_FREQ);
 }
 
 static struct psi_group *iterate_groups(struct task_struct *task, void **iter)
@@ -513,6 +511,7 @@ void psi_task_change(struct task_struct *task, int clear, int set)
 {
         int cpu = task_cpu(task);
         struct psi_group *group;
+        bool wake_clock = true;
         void *iter = NULL;
 
         if (!task->pid)
@@ -530,8 +529,22 @@ void psi_task_change(struct task_struct *task, int clear, int set)
         task->psi_flags &= ~clear;
         task->psi_flags |= set;
 
-        while ((group = iterate_groups(task, &iter)))
+        /*
+         * Periodic aggregation shuts off if there is a period of no
+         * task changes, so we wake it back up if necessary. However,
+         * don't do this if the task change is the aggregation worker
+         * itself going to sleep, or we'll ping-pong forever.
+         */
+        if (unlikely((clear & TSK_RUNNING) &&
+                     (task->flags & PF_WQ_WORKER) &&
+                     wq_worker_last_func(task) == psi_update_work))
+                wake_clock = false;
+
+        while ((group = iterate_groups(task, &iter))) {
                 psi_group_change(group, cpu, clear, set);
+                if (wake_clock && !delayed_work_pending(&group->clock_work))
+                        schedule_delayed_work(&group->clock_work, PSI_FREQ);
+        }
 }
 
 void psi_memstall_tick(struct task_struct *task, int cpu)