Re: [PATCH 2/2] mac80211: Fixing Races for skipping tailroom reservation

[Yogesh Ashok Powar <yogeshp@marvell.com>]

On Tue, Jun 21, 2011 at 07:40:15AM -0700, Johannes Berg wrote:
> On Tue, 2011-06-21 at 19:40 +0530, Yogesh Ashok Powar wrote:
> 
> > @@ -455,6 +496,8 @@ int ieee80211_key_link(struct ieee80211_key *key,
> >  	__ieee80211_key_replace(sdata, sta, pairwise, old_key, key);
> >  	__ieee80211_key_destroy(old_key);
> >  
> > +	increment_tailroom_need_count(key->local);
> > +
> 
> This doesn't seem right -- it links the key in first and then does the
> update, the mechanism I described relies on doing it the other way
> around.
In that case we should have something like this

@@ -493,11 +493,11 @@ int ieee80211_key_link(struct ieee80211_key *key,
 	else
 		old_key = key_mtx_dereference(sdata->local, sdata->keys[idx]);
 
+	increment_tailroom_need_count(key->local);
+
 	__ieee80211_key_replace(sdata, sta, pairwise, old_key, key);
 	__ieee80211_key_destroy(old_key);
 
-	increment_tailroom_need_count(key->local);
-
 	ieee80211_debugfs_key_add(key);
 
 	ret = ieee80211_key_enable_hw_accel(key);

> 
> > @@ -498,8 +541,12 @@ void ieee80211_enable_keys(struct ieee80211_sub_if_data *sdata)
> >  
> >  	mutex_lock(&sdata->local->key_mtx);
> >  
> > -	list_for_each_entry(key, &sdata->key_list, list)
> > +	sdata->local->crypto_tx_tailroom_needed_cnt = 0;
> > +
> 
> That doesn't seem right either -- only if you have a single sdata that
> will work, I think?
Right. For multiple sdata count will be over written to 0.

I think, following should fix this

Thanks
Yogesh

diff --git a/net/mac80211/key.c b/net/mac80211/key.c
index edf9f40..0bf450d 100644
--- a/net/mac80211/key.c
+++ b/net/mac80211/key.c
@@ -541,8 +541,6 @@ void ieee80211_enable_keys(struct ieee80211_sub_if_data *sdata)
 
 	mutex_lock(&sdata->local->key_mtx);
 
-	sdata->local->crypto_tx_tailroom_needed_cnt = 0;
-
 	list_for_each_entry(key, &sdata->key_list, list) {
 		increment_tailroom_need_count(sdata->local);
 		ieee80211_key_enable_hw_accel(key);
diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index 05e3fb8..bef3bdd 100644
--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -1271,6 +1271,9 @@ int ieee80211_reconfig(struct ieee80211_local *local)
 		mutex_unlock(&local->sta_mtx);
 	}
 
+	/* Reset tailroom skip count */
+	local->crypto_tx_tailroom_needed_cnt = 0;
+
 	/* add back keys */
 	list_for_each_entry(sdata, &local->interfaces, list)
 		if (ieee80211_sdata_running(sdata))