Re: [PATCH] cfg80211: Pass lockdep expression to RCU lists

[Arend Van Spriel <arend.vanspriel@broadcom.com>]

On 2/19/2020 10:29 PM, Johannes Berg wrote:
> On Wed, 2020-02-19 at 22:27 +0100, Arend Van Spriel wrote:
>> On 2/19/2020 10:13 AM, Johannes Berg wrote:
>>> On Wed, 2020-02-19 at 14:41 +0530, Amol Grover wrote:
>>>>    
>>>> -	WARN_ON_ONCE(!rcu_read_lock_held() && !lockdep_rtnl_is_held());
>>>> -
>>>> -	list_for_each_entry_rcu(pos, &rdev->sched_scan_req_list, list) {
>>>> +	list_for_each_entry_rcu(pos, &rdev->sched_scan_req_list, list,
>>>> +				lockdep_rtnl_is_held()) {
>>>
>>> Huh, I didn't even know you _could_ do that :)
>>
>> Me neither ;-). Above you are removing the WARN_ON_ONCE() entirely.
>> Would it not be good to keep the WARN_ON_ONCE() with only the
>> !rcu_read_lock_held() check.
> 
> Not needed, the macro expansion will already contain
> rcu_read_lock_any_held() just like in all the other cases where you pass
> a lockdep condition to RCU helpers.

Ah, yes. I see it in __list_check_rcu().

Thanks,
Arend