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A last minute cgroup bandwidth scheduling fix for a recently

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introduced logic fail which triggered a kernel warning by
 LTP's cfs_bandwidth01.
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'sched-urgent-2021-06-24' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler fix from Ingo Molnar:
 "A last minute cgroup bandwidth scheduling fix for a recently
  introduced logic fail which triggered a kernel warning by LTP's
  cfs_bandwidth01 test"

* tag 'sched-urgent-2021-06-24' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/fair: Ensure that the CFS parent is added after unthrottling
This commit is contained in:
Linus Torvalds 2021-06-24 08:58:23 -07:00
commit 666751701b
1 changed files with 28 additions and 0 deletions
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28
kernel/sched/fair.c
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@ -3298,6 +3298,31 @@ 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 whether 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)
{
@ -3313,6 +3338,9 @@ 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;
}