From 3780d038fdf4b5ef26ead10b0604ab1f46dd9510 Mon Sep 17 00:00:00 2001 From: Stanislaw Gruszka Date: Fri, 9 Mar 2012 12:39:54 +0100 Subject: [PATCH] rt2x00: fix random stalls Is possible that we stop queue and then do not wake up it again, especially when packets are transmitted fast. That can be easily reproduced with modified tx queue entry_num to some small value e.g. 16. If mac80211 already hold local->queue_stop_reason_lock, then we can wait on that lock in both rt2x00queue_pause_queue() and rt2x00queue_unpause_queue(). After drooping ->queue_stop_reason_lock is possible that __ieee80211_wake_queue() will be performed before __ieee80211_stop_queue(), hence we stop queue and newer wake up it again. Another race condition is possible when between rt2x00queue_threshold() check and rt2x00queue_pause_queue() we will process all pending tx buffers on different cpu. This might happen if for example interrupt will be triggered on cpu performing rt2x00mac_tx(). To prevent race conditions serialize pause/unpause by queue->tx_lock. Cc: stable@vger.kernel.org Signed-off-by: Stanislaw Gruszka Acked-by: Gertjan van Wingerde Signed-off-by: John W. Linville --- drivers/net/wireless/rt2x00/rt2x00dev.c | 6 +++++- drivers/net/wireless/rt2x00/rt2x00mac.c | 9 +++++++++ drivers/net/wireless/rt2x00/rt2x00queue.c | 3 +++ 3 files changed, 17 insertions(+), 1 deletion(-) diff --git a/drivers/net/wireless/rt2x00/rt2x00dev.c b/drivers/net/wireless/rt2x00/rt2x00dev.c index d2a1ea98d0f2..fd356b7c0476 100644 --- a/drivers/net/wireless/rt2x00/rt2x00dev.c +++ b/drivers/net/wireless/rt2x00/rt2x00dev.c @@ -426,10 +426,14 @@ void rt2x00lib_txdone(struct queue_entry *entry, /* * If the data queue was below the threshold before the txdone * handler we must make sure the packet queue in the mac80211 stack - * is reenabled when the txdone handler has finished. + * is reenabled when the txdone handler has finished. This has to be + * serialized with rt2x00mac_tx(), otherwise we can wake up queue + * before it was stopped. */ + spin_lock_bh(&entry->queue->tx_lock); if (!rt2x00queue_threshold(entry->queue)) rt2x00queue_unpause_queue(entry->queue); + spin_unlock_bh(&entry->queue->tx_lock); } EXPORT_SYMBOL_GPL(rt2x00lib_txdone); diff --git a/drivers/net/wireless/rt2x00/rt2x00mac.c b/drivers/net/wireless/rt2x00/rt2x00mac.c index ede3c58e6783..2df2eb6d3e06 100644 --- a/drivers/net/wireless/rt2x00/rt2x00mac.c +++ b/drivers/net/wireless/rt2x00/rt2x00mac.c @@ -152,13 +152,22 @@ void rt2x00mac_tx(struct ieee80211_hw *hw, struct sk_buff *skb) if (unlikely(rt2x00queue_write_tx_frame(queue, skb, false))) goto exit_fail; + /* + * Pausing queue has to be serialized with rt2x00lib_txdone(). Note + * we should not use spin_lock_bh variant as bottom halve was already + * disabled before ieee80211_xmit() call. + */ + spin_lock(&queue->tx_lock); if (rt2x00queue_threshold(queue)) rt2x00queue_pause_queue(queue); + spin_unlock(&queue->tx_lock); return; exit_fail: + spin_lock(&queue->tx_lock); rt2x00queue_pause_queue(queue); + spin_unlock(&queue->tx_lock); exit_free_skb: ieee80211_free_txskb(hw, skb); } diff --git a/drivers/net/wireless/rt2x00/rt2x00queue.c b/drivers/net/wireless/rt2x00/rt2x00queue.c index 5adfb3eab9cd..9b1b2b7a7807 100644 --- a/drivers/net/wireless/rt2x00/rt2x00queue.c +++ b/drivers/net/wireless/rt2x00/rt2x00queue.c @@ -619,6 +619,9 @@ int rt2x00queue_write_tx_frame(struct data_queue *queue, struct sk_buff *skb, else if (test_bit(REQUIRE_DMA, &queue->rt2x00dev->cap_flags)) rt2x00queue_align_frame(skb); + /* + * That function must be called with bh disabled. + */ spin_lock(&queue->tx_lock); if (unlikely(rt2x00queue_full(queue))) { -- 2.20.1