The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 7c7ad626d9a0ff0a36c1e2a3cfbbc6a13828d5eb Mon Sep 17 00:00:00 2001

From: Vincent Guittot vincent.guittot@linaro.org Date: Thu, 27 May 2021 14:29:15 +0200 Subject: [PATCH] sched/fair: Keep load_avg and load_sum synced

when removing a cfs_rq from the list we only check _sum value so we must ensure that _avg and _sum stay synced so load_sum can't be null whereas load_avg is not after propagating load in the cgroup hierarchy.

Use load_avg to compute load_sum similarly to what is done for util_sum and runnable_sum.

Fixes: 0e2d2aaaae52 ("sched/fair: Rewrite PELT migration propagation") Reported-by: Odin Ugedal odin@uged.al Signed-off-by: Vincent Guittot vincent.guittot@linaro.org Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Reviewed-by: Odin Ugedal odin@uged.al Link: https://lkml.kernel.org/r/20210527122916.27683-2-vincent.guittot@linaro.org

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 3248e24a90b0..f4795b800841 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3499,10 +3499,9 @@ update_tg_cfs_runnable(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cf static inline void update_tg_cfs_load(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq) { - long delta_avg, running_sum, runnable_sum = gcfs_rq->prop_runnable_sum; + long delta, running_sum, runnable_sum = gcfs_rq->prop_runnable_sum; unsigned long load_avg; u64 load_sum = 0; - s64 delta_sum; u32 divider;

if (!runnable_sum) @@ -3549,13 +3548,13 @@ update_tg_cfs_load(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq load_sum = (s64)se_weight(se) * runnable_sum; load_avg = div_s64(load_sum, divider);

- delta_sum = load_sum - (s64)se_weight(se) * se->avg.load_sum; - delta_avg = load_avg - se->avg.load_avg; + delta = load_avg - se->avg.load_avg;

se->avg.load_sum = runnable_sum; se->avg.load_avg = load_avg; - add_positive(&cfs_rq->avg.load_avg, delta_avg); - add_positive(&cfs_rq->avg.load_sum, delta_sum); + + add_positive(&cfs_rq->avg.load_avg, delta); + cfs_rq->avg.load_sum = cfs_rq->avg.load_avg * divider; }

static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum)