[PATCH 10/15] wifi: iwlwifi: read txq->read_ptr under lock

[Miri Korenblit <miriam.rachel.korenblit@intel.com>]

From: Johannes Berg <johannes.berg@intel.com>

If we read txq->read_ptr without lock, we can read the same
value twice, then obtain the lock, and reclaim from there
to two different places, but crucially reclaim the same
entry twice, resulting in the WARN_ONCE() a little later.
Fix that by reading txq->read_ptr under lock.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
---
 drivers/net/wireless/intel/iwlwifi/queue/tx.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/wireless/intel/iwlwifi/queue/tx.c b/drivers/net/wireless/intel/iwlwifi/queue/tx.c
index 33973a60d0bf..6229c785c845 100644
--- a/drivers/net/wireless/intel/iwlwifi/queue/tx.c
+++ b/drivers/net/wireless/intel/iwlwifi/queue/tx.c
@@ -1589,9 +1589,9 @@ void iwl_txq_reclaim(struct iwl_trans *trans, int txq_id, int ssn,
 		return;
 
 	tfd_num = iwl_txq_get_cmd_index(txq, ssn);
-	read_ptr = iwl_txq_get_cmd_index(txq, txq->read_ptr);
 
 	spin_lock_bh(&txq->lock);
+	read_ptr = iwl_txq_get_cmd_index(txq, txq->read_ptr);
 
 	if (!test_bit(txq_id, trans->txqs.queue_used)) {
 		IWL_DEBUG_TX_QUEUES(trans, "Q %d inactive - ignoring idx %d\n",
-- 
2.34.1