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Re: [PATCH] mac80211: restrict delayed tailroom needed decrement

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On 7/9/2018 2:56 PM, Johannes Berg wrote:
On Mon, 2018-07-09 at 14:54 +0530, Manikanta Pubbisetty wrote:

This describes a scenario where there's *unnecessary* work done, but not
really one where we have something that's *incorrect*?

To me at least doing unnecessary things is incorrect :-D, may be we can
change the statement.
Well, I guess it's a question of semantics, but this doesn't really
result in any observable incorrect behaviour.

Okay.

Are you saying that you found a problem with this? Did this show up in
some sort of measurements?
Not really, I have observed in my testing that there were warnings
whenever a AP_VLAN was brought down; this is done in ieee80211_free_keys.
Warnings show up every time we bring down the AP_VLAN interface(using
ifconfig); warnings apart but I thought there would be unnecessary
overhead in the tailroom expansion though the overhead may be trivial.
Except for that maybe :-)

:-)

+++ b/net/mac80211/key.c
@@ -583,7 +583,8 @@ static void __ieee80211_key_destroy(struct ieee80211_key *key,
ieee80211_debugfs_key_remove(key); - if (delay_tailroom) {
+		if (delay_tailroom &&
+		    sdata->vif.type == NL80211_IFTYPE_STATION) {
   			/* see ieee80211_delayed_tailroom_dec */
   			sdata->crypto_tx_tailroom_pending_dec++;
   			schedule_delayed_work(&sdata->dec_tailroom_needed_wk,
I think you'd better change the caller, i.e. ieee80211_del_key(), and a
add a comment there that explains what's going on.
Not really sure what you were trying to tell here.
I think you should do

ieee80211_key_destroy(..., type == STATION);

Even this would boil down to the same behavior, no?


in the caller, instead of hard-coding the thing here.

There may be more places that want the delay, perhaps for other reasons?

I was going through the source to figure out that; but all that I could understand is this was mainly done to improve roam time.



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