On 4/9/24 12:57, Johannes Berg wrote:
On Tue, 2024-04-09 at 09:27 +0530, Aditya Kumar Singh wrote:
On 4/8/24 23:55, Johannes Berg wrote:
On Tue, 2024-03-26 at 20:41 +0530, Aditya Kumar Singh wrote:
@@ -1232,7 +1256,9 @@ ieee80211_assign_beacon(struct ieee80211_sub_if_data *sdata,
}
rcu_assign_pointer(link->u.ap.beacon, new);
- sdata->u.ap.active = true;
+
+ if (ieee80211_num_beaconing_links(sdata) <= 1)
+ sdata->u.ap.active = true;
I don't understand this change. Neither the <= 1 really, nor the fact
that you actually _make_ this change.
The place above where we are checking number of beaconing links, at that
point at least 1 should be active. Since before checking, we have done
rcu_assign_pointer() so at least 1 should be there. That is why that
condition.
If it is more than 1, then this is not the first link which is going to
come up and hence there is no need to set the flag again.
Hmm, OK, I guess that makes some sense. However, it's also completely
pointless, since setting it =true when it's already =true doesn't really
do anything. Adding the code seems to imply it should avoid setting it
in some cases, which isn't actually the case.
Besides, doing the counting is almost certainly far more expensive than
simply setting it to true when it's already true. Certainly the state
should be =true after this function is called.
If you really think the extra write might be a problem (it isn't though)
then you'd still want to write it as "if (!active) active=true" since
that's actually checking the right thing. But ... that really wouldn't
matter in all but the highest-performance code meant to deal with high
(CPU/core) parallelism.
So this is just a long-winded way of saying: don't do that, just keep it
unconditionally setting active.
Well, that's true. Just to have symmetry in beaconing up and tear down I
did like that but it seems costly as you said. I will instead go with
!active thing as you suggested. Thanks for your inputs. Will send v2
soon for review.
@@ -1486,7 +1488,10 @@ static int ieee80211_start_ap(struct wiphy *wiphy, struct net_device *dev,
if (old)
kfree_rcu(old, rcu_head);
RCU_INIT_POINTER(link->u.ap.beacon, NULL);
- sdata->u.ap.active = false;
+
+ if (!ieee80211_num_beaconing_links(sdata))
+ sdata->u.ap.active = false;
== 0 maybe?
Yeah can do. I prefer "!expr" over "expr == 0". Do you have any preference?
I think for something that actually _counts_, like here, I'd (slightly)
prefer ==0. It's obviously equivalent, but it seems more natural to
write "is number of beaconing links equal to zero" rather than "is not
number of beaconing links".
I may be influenced too much by Dan's thoughts on the matter ;-)
https://staticthinking.wordpress.com/2024/02/20/when-to-use-0/
Yeah in this case it seems reasonable to use "== 0" instead. Will do
like this.
Or maybe we should just save/restore the value instead?
list_for_each_entry(vlan, &sdata->u.ap.vlans, u.vlan.list)
netif_carrier_off(vlan->dev);
- if (ieee80211_num_beaconing_links(sdata) <= 1)
Unrelated, but it looks like the VLAN netif_carrier_off() handling above
is also wrong and should really go into this if block as well.
Yeah MLO VLAN changes would do that? The previous change was focusing on
the AP mode alone and I did not want to break anything in VLAN so did
not touch it there.
Sure sure, just drive-by observation.
:)
