Re: [PATCH] sched/fair: Fix DELAY_DEQUEUE issue related to cgroup throttling

[Han Guangjiang]

>> When both CPU cgroup and memory cgroup are enabled with parent cgroup
>> resource limits much smaller than child cgroup's, the system frequently
>> hangs with NULL pointer dereference:
> Is it happening while running a specific workload ?
> Would it be possible to provide a reproducer ?

Hi,

Yes, this happens on our complex workload. We are using PREEMPT_RT option,
and from the error log, we can see that rt mutex PI operation is
being executed, and it needs to switch scheduler for a delay_dequeued task.
The parent group of this delay_dequeued task is being throttled by
cgroup at this time. And We currently do not have a minimal bug reproduction
program constructed.

similar issue: https://lore.kernel.org/all/87254ef1-fa58-4747-b2e1-5c85ecde15bf@xxxxxxxxxxxxx/
 
Thanks,
Han Guangjiang