linux-kernel - Re: [tip:sched/core] sched/fair: Fix O(nr

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Date:   Mon, 15 May 2017 11:43:05 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     pjt@...gle.com, efault@....de, tj@...nel.org, hpa@...or.com,
        torvalds@...ux-foundation.org, clm@...com, mingo@...nel.org,
        vincent.guittot@...aro.org, linux-kernel@...r.kernel.org,
        tglx@...utronix.de
Cc:     linux-tip-commits@...r.kernel.org
Subject: Re: [tip:sched/core] sched/fair: Fix O(nr_cgroups) in load balance
 path

On Mon, May 15, 2017 at 02:13:17AM -0700, tip-bot for Tejun Heo wrote:
> @@ -463,7 +464,7 @@ static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
>  {
>  }
>  
> -#define for_each_leaf_cfs_rq(rq, cfs_rq) \
> +#define for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos)	\
>  		for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
>  
>  static inline struct sched_entity *parent_entity(struct sched_entity *se)


That generates a build warn on CGROUP=n SCHED_DEBUG=y

This seems to cure..

Ingo, could you fold or append?

---
 kernel/sched/fair.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index ca08ae2a7877..219fe58e3023 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -465,7 +465,7 @@ static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
 }
 
 #define for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos)	\
-		for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
+		for (cfs_rq = &rq->cfs, pos = NULL; cfs_rq; cfs_rq = pos)
 
 static inline struct sched_entity *parent_entity(struct sched_entity *se)
 {