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From: Arik Nemtsov <arik@wizery.com>
To: <linux-wireless@vger.kernel.org>
Cc: Luciano Coelho <coelho@ti.com>,
	Johannes Berg <johannes@sipsolutions.net>,
	Arik Nemtsov <arik@wizery.com>
Subject: [PATCH 01/10] wl12xx: fix potential race condition with TX queue watermark
Date: Sun, 16 Jan 2011 07:42:05 +0200	[thread overview]
Message-ID: <1295156534-4178-2-git-send-email-arik@wizery.com> (raw)
In-Reply-To: <1295156534-4178-1-git-send-email-arik@wizery.com>

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@wizery.com>
---
 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 9076555..6163167 100644
--- a/drivers/net/wireless/wl12xx/main.c
+++ b/drivers/net/wireless/wl12xx/main.c
@@ -984,6 +984,17 @@ 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 */
@@ -998,19 +1009,6 @@ 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 2347f25..fdec4a3 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


  reply	other threads:[~2011-01-16  5:42 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-01-16  5:42 [PATCH 00/10] wl12xx: AP-mode per link PSM Arik Nemtsov
2011-01-16  5:42 ` Arik Nemtsov [this message]
2011-01-16  5:42 ` [PATCH 02/10] wl12xx: AP-mode - fix race condition on sta connection Arik Nemtsov
2011-01-26 14:01   ` Luciano Coelho
2011-01-26 20:04     ` Arik Nemtsov
2011-01-26 21:28       ` Luciano Coelho
2011-01-26 21:33   ` Johannes Berg
2011-01-26 21:44     ` Arik Nemtsov
2011-01-26 21:54       ` Johannes Berg
2011-01-26 22:02         ` Arik Nemtsov
2011-01-26 22:08           ` Johannes Berg
2011-01-26 22:16             ` Arik Nemtsov
2011-01-26 23:11               ` Johannes Berg
2011-01-27  0:20             ` Jouni Malinen
2011-01-27  8:21               ` Johannes Berg
2011-01-16  5:42 ` [PATCH 03/10] wl12xx: AP-mode - TX queue per link in AC Arik Nemtsov
2011-01-16  5:42 ` [PATCH 04/10] mac80211: do not calc frame duration when using HW rate-control Arik Nemtsov
2011-01-16  8:34   ` Johannes Berg
2011-01-16  5:42 ` [PATCH 05/10] wl12xx: report invalid TX rate when returning non-TX-ed skbs Arik Nemtsov
2011-01-27  9:51   ` Luciano Coelho
2011-01-27 10:33     ` Johannes Berg
2011-01-30  6:57       ` Arik Nemtsov
2011-01-16  5:42 ` [PATCH 06/10] mac80211: add HW flag for disabling auto link-PS in AP mode Arik Nemtsov
2011-01-16  8:50   ` Johannes Berg
     [not found]     ` <AANLkTik=WDsehr0EgW7QemfdmokvaLzg1ugASwiuCOXt@mail.gmail.com>
2011-01-16 21:53       ` Fwd: " Arik Nemtsov
2011-01-17  9:35         ` Johannes Berg
2011-01-17 22:47           ` Arik Nemtsov
2011-01-18  9:05             ` Johannes Berg
2011-01-18 19:17               ` Arik Nemtsov
2011-01-27 11:39   ` Luciano Coelho
2011-01-16  5:42 ` [PATCH 07/10] wl12xx: AP-mode - support HW based link PS monitoring Arik Nemtsov
2011-01-27 11:41   ` Luciano Coelho
2011-01-16  5:42 ` [PATCH 08/10] wl12xx: AP mode - fix bug in cleanup of wl1271_op_sta_add() Arik Nemtsov
2011-01-16  5:42 ` [PATCH 09/10] wl12xx: AP-mode - count free FW TX blocks per link Arik Nemtsov
2011-01-16  5:42 ` [PATCH 10/10] wl12xx: AP-mode - management of links in PS-mode Arik Nemtsov

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