Check the conditions for the high/low TX queue watermarks when the
spin-lock is taken. This prevents race conditions as tx_queue_count and
the flag checked are only modified when the spin-lock is taken.
The following race was in mind:
- Queues are almost full and wl1271_op_tx() will stop the queues, but it
doesn't get the spin-lock yet.
- (on another CPU) tx_work_locked() dequeues 15 skbs from this queue and
tx_queue_count is updated to reflect this
- wl1271_op_tx() does not check tx_queue_count after taking the
spin-lock and incorrectly stops the queue.
Signed-off-by: Arik Nemtsov <arik@xxxxxxxxxx>
---
drivers/net/wireless/wl12xx/main.c | 24 +++++++++++-------------
drivers/net/wireless/wl12xx/tx.c | 2 +-
2 files changed, 12 insertions(+), 14 deletions(-)
diff --git a/drivers/net/wireless/wl12xx/main.c b/drivers/net/wireless/wl12xx/main.c
index dfab21e..cf11bda 100644
--- a/drivers/net/wireless/wl12xx/main.c
+++ b/drivers/net/wireless/wl12xx/main.c
@@ -995,6 +995,17 @@ static int wl1271_op_tx(struct ieee80211_hw *hw, struct sk_buff *skb)
}
#endif
wl->tx_queue_count++;
+
+ /*
+ * The workqueue is slow to process the tx_queue and we need stop
+ * the queue here, otherwise the queue will get too long.
+ */
+ if (wl->tx_queue_count >= WL1271_TX_QUEUE_HIGH_WATERMARK) {
+ wl1271_debug(DEBUG_TX, "op_tx: stopping queues");
+ ieee80211_stop_queues(wl->hw);
+ __set_bit(WL1271_FLAG_TX_QUEUE_STOPPED, &wl->flags);
+ }
+
spin_unlock_irqrestore(&wl->wl_lock, flags);
/* queue the packet */
@@ -1009,19 +1020,6 @@ static int wl1271_op_tx(struct ieee80211_hw *hw, struct sk_buff *skb)
if (!test_bit(WL1271_FLAG_FW_TX_BUSY, &wl->flags))
ieee80211_queue_work(wl->hw, &wl->tx_work);
- /*
- * The workqueue is slow to process the tx_queue and we need stop
- * the queue here, otherwise the queue will get too long.
- */
- if (wl->tx_queue_count >= WL1271_TX_QUEUE_HIGH_WATERMARK) {
- wl1271_debug(DEBUG_TX, "op_tx: stopping queues");
-
- spin_lock_irqsave(&wl->wl_lock, flags);
- ieee80211_stop_queues(wl->hw);
- set_bit(WL1271_FLAG_TX_QUEUE_STOPPED, &wl->flags);
- spin_unlock_irqrestore(&wl->wl_lock, flags);
- }
-
return NETDEV_TX_OK;
}
diff --git a/drivers/net/wireless/wl12xx/tx.c b/drivers/net/wireless/wl12xx/tx.c
index 3507c81..ce9a19b 100644
--- a/drivers/net/wireless/wl12xx/tx.c
+++ b/drivers/net/wireless/wl12xx/tx.c
@@ -288,7 +288,7 @@ static void handle_tx_low_watermark(struct wl1271 *wl)
/* firmware buffer has space, restart queues */
spin_lock_irqsave(&wl->wl_lock, flags);
ieee80211_wake_queues(wl->hw);
- clear_bit(WL1271_FLAG_TX_QUEUE_STOPPED, &wl->flags);
+ __clear_bit(WL1271_FLAG_TX_QUEUE_STOPPED, &wl->flags);
spin_unlock_irqrestore(&wl->wl_lock, flags);
}
}
--
1.7.1
--
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