On Thu, Jan 23, 2020 at 02:42:03PM +0100, Toke Høiland-Jørgensen wrote:

Jesper Dangaard Brouer [off-list ref] writes:

quoted

On Thu, 23 Jan 2020 17:34:38 +0530
Amol Grover [off-list ref] wrote:

quoted

head is traversed using hlist_for_each_entry_rcu outside an
RCU read-side critical section but under the protection
of dtab->index_lock.

We do hold the lock in update and delete cases, but not in the lookup
cases.  Is it then still okay to add the lockdep_is_held() annotation?

I concluded 'yes' from the comment on hlist_for_each_entry_rcu():

The lockdep condition gets passed to this:

#define __list_check_rcu(dummy, cond, extra...)				\
	({								\
	check_arg_count_one(extra);					\
	RCU_LOCKDEP_WARN(!cond && !rcu_read_lock_any_held(),		\
			 "RCU-list traversed in non-reader section!");	\
	 })


so that seems fine :)

Yes, adding a lockdep expression will be okay. This is because an
implicit check is done to check if list_for_each_entry_rcu() is
traversed under RCU read-side critical section. In case the traversal is
outside RCU read-side critical section, the lockdep expression makes
sure the traversal is done under the mentioned lock.

Thanks
Amol

-Toke

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