Messages in this thread Patch in this message | | | From | Odin Ugedal <> | Date | Mon, 21 Jun 2021 14:42:23 +0200 | Subject | Re: [powerpc][5.13.0-rc7] Kernel warning (kernel/sched/fair.c:401) while running LTP tests |
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Hi,
Did some more research, and it looks like this is what happens:
$ tree /sys/fs/cgroup/ltp/ -d --charset=ascii /sys/fs/cgroup/ltp/ |-- drain `-- test-6851 `-- level2 |-- level3a | |-- worker1 | `-- worker2 `-- level3b `-- worker3
Timeline (ish): - worker3 gets throttled - level3b is decayed, since it has no more load - level2 get throttled - worker3 get unthrottled - level2 get unthrottled - worker3 is added to list - level3b is not added to list, since nr_running==0 and is decayed
The attached diff (based on https://lore.kernel.org/lkml/20210518125202.78658-3-odin@uged.al/) fixes the issue for me. Not the most elegant solution, but the simplest one as of now, and to show what is wrong.
Any thoughts Vincent?
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 */
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