Re: [PATCH] bpf: devmap: Pass lockdep expression to RCU lists

[Toke HÃiland-JÃrgensen]

Jesper Dangaard Brouer <brouer@xxxxxxxxxx> writes:

> On Thu, 23 Jan 2020 17:34:38 +0530
> Amol Grover <frextrite@xxxxxxxxx> wrote:
>
>> 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 :)

-Toke