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authorJohannes Berg <johannes.berg@intel.com>2011-05-13 13:35:40 +0200
committerJohn W. Linville <linville@tuxdriver.com>2011-05-16 14:10:40 -0400
commitec034b208dc8aa5dc73ec46c3f27e34c5efbf113 (patch)
tree56140fc3a4115441822b5cc2aa9de5224bcb8654 /net/mac80211/ht.c
parent7527a782e187d1214a5b3dc2897ce441033bb4ef (diff)
downloadlinux-ec034b208dc8aa5dc73ec46c3f27e34c5efbf113.tar.bz2
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>
Diffstat (limited to 'net/mac80211/ht.c')
-rw-r--r--net/mac80211/ht.c27
1 files changed, 21 insertions, 6 deletions
diff --git a/net/mac80211/ht.c b/net/mac80211/ht.c
index b9e4b9bd2179..9f5842a43111 100644
--- a/net/mac80211/ht.c
+++ b/net/mac80211/ht.c
@@ -140,14 +140,29 @@ void ieee80211_ba_session_work(struct work_struct *work)
sta, tid, WLAN_BACK_RECIPIENT,
WLAN_REASON_QSTA_TIMEOUT, true);
- tid_tx = sta->ampdu_mlme.tid_tx[tid];
- if (!tid_tx)
- continue;
+ tid_tx = sta->ampdu_mlme.tid_start_tx[tid];
+ if (tid_tx) {
+ /*
+ * Assign it over to the normal tid_tx array
+ * where it "goes live".
+ */
+ spin_lock_bh(&sta->lock);
+
+ sta->ampdu_mlme.tid_start_tx[tid] = NULL;
+ /* could there be a race? */
+ if (sta->ampdu_mlme.tid_tx[tid])
+ kfree(tid_tx);
+ else
+ ieee80211_assign_tid_tx(sta, tid, tid_tx);
+ spin_unlock_bh(&sta->lock);
- if (test_bit(HT_AGG_STATE_WANT_START, &tid_tx->state))
ieee80211_tx_ba_session_handle_start(sta, tid);
- else if (test_and_clear_bit(HT_AGG_STATE_WANT_STOP,
- &tid_tx->state))
+ continue;
+ }
+
+ tid_tx = sta->ampdu_mlme.tid_tx[tid];
+ if (tid_tx && test_and_clear_bit(HT_AGG_STATE_WANT_STOP,
+ &tid_tx->state))
___ieee80211_stop_tx_ba_session(sta, tid,
WLAN_BACK_INITIATOR,
true);