Hi,
On Mon, Mar 5, 2012 at 5:48 PM, Stanislaw Gruszka <sgruszka@xxxxxxxxxx> wrote:
> 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.
>
> To prevent stalls serialize pause/unpause by queue->tx_lock.
>
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Stanislaw Gruszka <sgruszka@xxxxxxxxxx>
> ---
> drivers/net/wireless/rt2x00/rt2x00dev.c | 10 ++++++++--
> drivers/net/wireless/rt2x00/rt2x00mac.c | 10 +++++++++-
> 2 files changed, 17 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/net/wireless/rt2x00/rt2x00dev.c b/drivers/net/wireless/rt2x00/rt2x00dev.c
> index 49a51b4..6c64658 100644
> --- a/drivers/net/wireless/rt2x00/rt2x00dev.c
> +++ b/drivers/net/wireless/rt2x00/rt2x00dev.c
> @@ -430,10 +430,16 @@ 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 mac80211
> + * queue before it was stopped if someone else hold mac80211 internal
> + * local->queue_stop_reason_lock .
> */
> - if (!rt2x00queue_threshold(entry->queue))
> + if (!rt2x00queue_threshold(entry->queue)) {
> + spin_lock_irq(&entry->queue->tx_lock);
> rt2x00queue_unpause_queue(entry->queue);
> + spin_unlock_irq(&entry->queue->tx_lock);
Why do we need to disable interrupts here? spin_lock_bh should
be sufficient.
> + }
> }
> EXPORT_SYMBOL_GPL(rt2x00lib_txdone);
>
> diff --git a/drivers/net/wireless/rt2x00/rt2x00mac.c b/drivers/net/wireless/rt2x00/rt2x00mac.c
> index ede3c58..2880512 100644
> --- a/drivers/net/wireless/rt2x00/rt2x00mac.c
> +++ b/drivers/net/wireless/rt2x00/rt2x00mac.c
> @@ -152,13 +152,21 @@ void rt2x00mac_tx(struct ieee80211_hw *hw, struct sk_buff *skb)
> if (unlikely(rt2x00queue_write_tx_frame(queue, skb, false)))
> goto exit_fail;
>
> - if (rt2x00queue_threshold(queue))
> + /*
> + * Pausing queue has to be serialized with rt2x00lib_txdone .
> + */
> + if (rt2x00queue_threshold(queue)) {
> + spin_lock(&queue->tx_lock);
> 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);
> }
> --
> 1.7.1
>
> --
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