On 9/19/19 1:14 PM, Vlad Buslov wrote:
> Recent changes that removed rtnl dependency from rules update path of tc
> also made tcf_block_put() function sleeping. This function is called from
> ops->destroy() of several Qdisc implementations, which in turn is called by
> qdisc_put(). Some Qdiscs call qdisc_put() while holding sch tree spinlock,
> which results sleeping-while-atomic BUG.
>
Note that calling qdisc_put() while holding sch tree lock can also
trigger deadlocks.
For example sch_pie.c has a del_timer_sync() in pie_destroy(),
while the pie_timer() timer handler acquires the root_lock.
(there are other cases like that, SFQ for example)
