Messages in this thread | | | Date | Tue, 21 Jun 2016 23:10:54 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH] sched/fair: initialize throttle_count for new task-groups lazily |
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On Thu, Jun 16, 2016 at 03:57:01PM +0300, Konstantin Khlebnikov wrote: > Cgroup created inside throttled group must inherit current throttle_count. > Broken throttle_count allows to nominate throttled entries as a next buddy, > later this leads to null pointer dereference in pick_next_task_fair(). > > This patch initialize cfs_rq->throttle_count at first enqueue: laziness > allows to skip locking all rq at group creation. Lazy approach also allows > to skip full sub-tree scan at throttling hierarchy (not in this patch).
You're talking about taking rq->lock in alloc_fair_sched_group(), right?
We're about to go do that anyway... But I suppose for backports this makes sense. Doing it at creation time also avoids the issues Ben raised, right?
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