Re: [PATCH] sched/fair: Fix RCU stall upon ENOMEM at sched_create_group().

From: Peter Zijlstra
Date: Tue Jan 06 2015 - 09:10:32 EST


On Thu, Dec 25, 2014 at 10:10:45PM +0900, Tetsuo Handa wrote:
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index ef2b104..586ee15 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -7756,8 +7756,12 @@ static void task_move_group_fair(struct task_struct *p, int queued)
> void free_fair_sched_group(struct task_group *tg)
> {
> int i;
> + struct cfs_bandwidth *cfs_b;
>
> - destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));
> + /* Check whether init_cfs_bandwidth() was called. */
> + cfs_b = tg_cfs_bandwidth(tg);
> + if (cfs_b->throttled_cfs_rq.next)
> + destroy_cfs_bandwidth(cfs_b);
>
> for_each_possible_cpu(i) {
> if (tg->cfs_rq)

This doesn't actually compile for !CONFIG_CFS_BANDWIDTH, how about:

---
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4005,6 +4005,10 @@ void __start_cfs_bandwidth(struct cfs_ba

static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
+ /* init_cfs_bandwidth() was not called */
+ if (!cfs_b->throttled_cfs_rq.next)
+ return;
+
hrtimer_cancel(&cfs_b->period_timer);
hrtimer_cancel(&cfs_b->slack_timer);
}
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