[PATCH] fixup: sched: Warn on long periods of pending need_resched

[Josh Don]

---
 kernel/sched/core.c | 29 ++++++++++++-----------------
 1 file changed, 12 insertions(+), 17 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 6fdf15eebc0d..c07a4c17205f 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -61,17 +61,13 @@ const_debug unsigned int sysctl_sched_features =

 /*
  * Print a warning if need_resched is set for the given duration (if
- * resched_latency_warn_enabled is set).
+ * LATENCY_WARN is enabled).
  *
  * If sysctl_resched_latency_warn_once is set, only one warning will be shown
  * per boot.
- *
- * Resched latency will be ignored for the first resched_boot_quiet_sec, to
- * reduce false alarms.
  */
-int sysctl_resched_latency_warn_ms = 100;
-int sysctl_resched_latency_warn_once = 1;
-static const long resched_boot_quiet_sec = 600;
+__read_mostly int sysctl_resched_latency_warn_ms = 100;
+__read_mostly int sysctl_resched_latency_warn_once = 1;
 #endif /* CONFIG_SCHED_DEBUG */

 /*
@@ -4542,20 +4538,19 @@ unsigned long long task_sched_runtime(struct
task_struct *p)
 }

 #ifdef CONFIG_SCHED_DEBUG
-static u64 resched_latency_check(struct rq *rq)
+static u64 cpu_resched_latency(struct rq *rq)
 {
  int latency_warn_ms = READ_ONCE(sysctl_resched_latency_warn_ms);
- u64 need_resched_latency, now = rq_clock(rq);
+ u64 resched_latency, now = rq_clock(rq);
  static bool warned_once;

  if (sysctl_resched_latency_warn_once && warned_once)
  return 0;

- if (!need_resched() || WARN_ON_ONCE(latency_warn_ms < 2))
+ if (!need_resched() || !latency_warn_ms)
  return 0;

- /* Disable this warning for the first few mins after boot */
- if (now < resched_boot_quiet_sec * NSEC_PER_SEC)
+ if (system_state == SYSTEM_BOOTING)
  return 0;

  if (!rq->last_seen_need_resched_ns) {
@@ -4565,13 +4560,13 @@ static u64 resched_latency_check(struct rq *rq)
  }

  rq->ticks_without_resched++;
- need_resched_latency = now - rq->last_seen_need_resched_ns;
- if (need_resched_latency <= latency_warn_ms * NSEC_PER_MSEC)
+ resched_latency = now - rq->last_seen_need_resched_ns;
+ if (resched_latency <= latency_warn_ms * NSEC_PER_MSEC)
  return 0;

  warned_once = true;

- return need_resched_latency;
+ return resched_latency;
 }

 static int __init setup_resched_latency_warn_ms(char *str)
@@ -4588,7 +4583,7 @@ static int __init setup_resched_latency_warn_ms(char *str)
 }
 __setup("resched_latency_warn_ms=", setup_resched_latency_warn_ms);
 #else
-static inline u64 resched_latency_check(struct rq *rq) { return 0; }
+static inline u64 cpu_resched_latency(struct rq *rq) { return 0; }
 #endif /* CONFIG_SCHED_DEBUG */

 /*
@@ -4614,7 +4609,7 @@ void scheduler_tick(void)
  update_thermal_load_avg(rq_clock_thermal(rq), rq, thermal_pressure);
  curr->sched_class->task_tick(rq, curr, 0);
  if (sched_feat(LATENCY_WARN))
- resched_latency = resched_latency_check(rq);
+ resched_latency = cpu_resched_latency(rq);
  calc_global_load_tick(rq);

  rq_unlock(rq, &rf);
-- 
2.31.0.291.g576ba9dcdaf-goog