Re: [powerpc][5.13.0-rc7] Kernel warning (kernel/sched/fair.c:401) while running LTP tests

---
 kernel/sched/fair.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index ea7de54cb022..e751061a9449 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c

@@ -3272,6 +3272,31 @@ static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq, int flags)

 #ifdef CONFIG_SMP
 #ifdef CONFIG_FAIR_GROUP_SCHED
+/*
+ * Because list_add_leaf_cfs_rq always places a child cfs_rq on the list
+ * immediately before a parent cfs_rq, and cfs_rqs are removed from the list
+ * bottom-up, we only have to test whether the cfs_rq before us on the list
+ * is our child.
+ * If cfs_rq is not on the list, test wether a child needs its to be added to
+ * connect a branch to the tree  * (see list_add_leaf_cfs_rq() for details).
+ */
+static inline bool child_cfs_rq_on_list(struct cfs_rq *cfs_rq)
+{
+       struct cfs_rq *prev_cfs_rq;
+       struct list_head *prev;
+
+       if (cfs_rq->on_list) {
+               prev = cfs_rq->leaf_cfs_rq_list.prev;
+       } else {
+               struct rq *rq = rq_of(cfs_rq);
+
+               prev = rq->tmp_alone_branch;
+       }
+
+       prev_cfs_rq = container_of(prev, struct cfs_rq, leaf_cfs_rq_list);
+
+       return (prev_cfs_rq->tg->parent == cfs_rq->tg);
+}

 static inline bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq)
 {

@@ -3287,6 +3312,9 @@ static inline bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq)
        if (cfs_rq->avg.runnable_sum)
                return false;

+       if (child_cfs_rq_on_list(cfs_rq))
+               return false;
+
        return true;
 }

--

2.17.1

quoted

Thanks
Odin

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index bfaa6e1f6067..aa32e9c29efd 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c

@@ -376,7 +376,8 @@ static inline bool list_add_leaf_cfs_rq(struct

cfs_rq *cfs_rq)
        return false;
 }

-static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
+/* Returns 1 if cfs_rq was present in the list and removed */
+static inline bool list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
 {
        if (cfs_rq->on_list) {
                struct rq *rq = rq_of(cfs_rq);

@@ -393,7 +394,9 @@ static inline void list_del_leaf_cfs_rq(struct

cfs_rq *cfs_rq)

                list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
                cfs_rq->on_list = 0;
+               return 1;
        }
+       return 0;
 }

 static inline void assert_list_leaf_cfs_rq(struct rq *rq)

@@ -3298,24 +3301,6 @@ static inline void cfs_rq_util_change(struct

cfs_rq *cfs_rq, int flags)

 #ifdef CONFIG_SMP
 #ifdef CONFIG_FAIR_GROUP_SCHED
-
-static inline bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq)
-{
-       if (cfs_rq->load.weight)
-               return false;
-
-       if (cfs_rq->avg.load_sum)
-               return false;
-
-       if (cfs_rq->avg.util_sum)
-               return false;
-
-       if (cfs_rq->avg.runnable_sum)
-               return false;
-
-       return true;
-}
-
 /**
  * update_tg_load_avg - update the tg's load avg
  * @cfs_rq: the cfs_rq whose avg changed

@@ -4109,11 +4094,6 @@ static inline void update_misfit_status(struct

task_struct *p, struct rq *rq)

 #else /* CONFIG_SMP */

-static inline bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq)
-{
-       return true;
-}
-
 #define UPDATE_TG      0x0
 #define SKIP_AGE_LOAD  0x0
 #define DO_ATTACH      0x0

@@ -4771,10 +4751,11 @@ static int tg_unthrottle_up(struct task_group

*tg, void *data)
        if (!cfs_rq->throttle_count) {
                cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
                                             cfs_rq->throttled_clock_task;
-
-               /* Add cfs_rq with load or one or more already running
entities to the list */
-               if (!cfs_rq_is_decayed(cfs_rq) || cfs_rq->nr_running)
+               if (cfs_rq->insert_on_unthrottle) {
                        list_add_leaf_cfs_rq(cfs_rq);
+                       if (tg->parent)
+
tg->parent->cfs_rq[cpu_of(rq)]->insert_on_unthrottle = true;
+                       }
        }

        return 0;

@@ -4788,7 +4769,7 @@ static int tg_throttle_down(struct task_group

*tg, void *data)
        /* group is entering throttled state, stop time */
        if (!cfs_rq->throttle_count) {
                cfs_rq->throttled_clock_task = rq_clock_task(rq);
-               list_del_leaf_cfs_rq(cfs_rq);
+               cfs_rq->insert_on_unthrottle = list_del_leaf_cfs_rq(cfs_rq);
        }
        cfs_rq->throttle_count++;

@@ -8019,6 +8000,23 @@ static bool __update_blocked_others(struct rq

*rq, bool *done)

 #ifdef CONFIG_FAIR_GROUP_SCHED

+static inline bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq)
+{
+       if (cfs_rq->load.weight)
+               return false;
+
+       if (cfs_rq->avg.load_sum)
+               return false;
+
+       if (cfs_rq->avg.util_sum)
+               return false;
+
+       if (cfs_rq->avg.runnable_sum)
+               return false;
+
+       return true;
+}
+
 static bool __update_blocked_fair(struct rq *rq, bool *done)
 {
        struct cfs_rq *cfs_rq, *pos;

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index a189bec13729..12a707d99ee6 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h

@@ -602,6 +602,7 @@ struct cfs_rq {
        u64                     throttled_clock_task_time;
        int                     throttled;
        int                     throttle_count;
+       int                     insert_on_unthrottle;
        struct list_head        throttled_list;
 #endif /* CONFIG_CFS_BANDWIDTH */
 #endif /* CONFIG_FAIR_GROUP_SCHED */