mac80211: fix TX a-MPDU locking

During my quest to make mac80211 not have any RCU
warnings from sparse, I came across the a-MPDU code
again and it wasn't quite clear why it isn't racy.
So instead of assigning the tid_tx array with just
the spinlock held in ieee80211_start_tx_ba_session
use a separate temporary array protected only by
the spinlock and protect all assignments to the
"live" array by both the spinlock and the mutex so
that other code is easily verified to be correct.

Due to pointer assignment atomicity I don't think
this is a real issue, but I'm not sure, especially
on Alpha the current code might be problematic.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/net/mac80211/sta_info.h b/net/mac80211/sta_info.h
index f00b4dcb49d7..55c51855ceb7 100644
--- a/net/mac80211/sta_info.h
+++ b/net/mac80211/sta_info.h
@@ -152,6 +152,7 @@ struct tid_ampdu_rx {
  *
  * @tid_rx: aggregation info for Rx per TID -- RCU protected
  * @tid_tx: aggregation info for Tx per TID
+ * @tid_start_tx: sessions where start was requested
  * @addba_req_num: number of times addBA request has been sent.
  * @dialog_token_allocator: dialog token enumerator for each new session;
  * @work: work struct for starting/stopping aggregation
@@ -168,6 +169,7 @@ struct sta_ampdu_mlme {
         /* tx */
         struct work_struct work;
         struct tid_ampdu_tx *tid_tx[STA_TID_NUM];
+        struct tid_ampdu_tx *tid_start_tx[STA_TID_NUM];
         u8 addba_req_num[STA_TID_NUM];
         u8 dialog_token_allocator;
 };
@@ -398,6 +400,8 @@ static inline u32 get_sta_flags(struct sta_info *sta)
         return ret;
 }
 
+void ieee80211_assign_tid_tx(struct sta_info *sta, int tid,
+                             struct tid_ampdu_tx *tid_tx);
 
 
 #define STA_HASH_SIZE 256