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

[Arend Van Spriel]

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