Q. drm/i915 shrinker, synchronize_rcu_expedited() from handlers

[J. R. Okajima]

Hello,

Since v4.11-rc7 I can see the workqueue stops on my development/test system.
Git-bisecting tells me the suspicious commit is
	c053b5a 2017-04-11 drm/i915: Don't call synchronize_rcu_expedited under struct_mutex

I am not sure whether this is the real cause or not of my problem, but I
have a question.
By the commit, the shrinker handlers ->scan_objects() and
->count_objects() both calls synchronize_rcu_expedited()
unconditionally. Is it a legal RCU bahavour?

I know dev->struct_mutex is unlocked now, but before the commit, these
two handlers were not calling synchronize_rcu_expedited().


J. R. Okajima