rt2x00: Serialize TX operations on a queue.

The rt2x00 driver gets frequent occurrences of the following error message
when operating under load:
phy0 -> rt2x00queue_write_tx_frame: Error - Arrived at non-free entry in the
non-full queue 2.

This is caused by simultaneous attempts from mac80211 to send a frame via
rt2x00, which are not properly serialized inside rt2x00queue_write_tx_frame,
causing the second frame to fail sending with the above mentioned error
message.

Fix this by introducing a per-queue spinlock to serialize the TX operations
on that queue.

Reported-by: Andreas Hartmann <andihartmann@01019freenet.de>
Signed-off-by: Gertjan van Wingerde <gwingerde@gmail.com>
Acked-by: Helmut Schaa <helmut.schaa@googlemail.com>
Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

2 files changed, 18 insertions, 5 deletions

diff --git a/drivers/net/wireless/rt2x00/rt2x00queue.c b/drivers/net/wireless/rt2x00/rt2x00queue.c
index c7fc9def6bcf..551cee1209ca 100644
--- a/drivers/net/wireless/rt2x00/rt2x00queue.c
+++ b/drivers/net/wireless/rt2x00/rt2x00queue.c
@@ -555,15 +555,21 @@ int rt2x00queue_write_tx_frame(struct data_queue *queue, struct sk_buff *skb,
                                bool local)
 {
         struct ieee80211_tx_info *tx_info;
-        struct queue_entry *entry = rt2x00queue_get_entry(queue, Q_INDEX);
+        struct queue_entry *entry;
         struct txentry_desc txdesc;
         struct skb_frame_desc *skbdesc;
         u8 rate_idx, rate_flags;
+        int ret = 0;
+
+        spin_lock(&queue->tx_lock);
+
+        entry = rt2x00queue_get_entry(queue, Q_INDEX);
 
         if (unlikely(rt2x00queue_full(queue))) {
                 ERROR(queue->rt2x00dev,
                       "Dropping frame due to full tx queue %d.\n", queue->qid);
-                return -ENOBUFS;
+                ret = -ENOBUFS;
+                goto out;
         }
 
         if (unlikely(test_and_set_bit(ENTRY_OWNER_DEVICE_DATA,
@@ -572,7 +578,8 @@ int rt2x00queue_write_tx_frame(struct data_queue *queue, struct sk_buff *skb,
                       "Arrived at non-free entry in the non-full queue %d.\n"
                       "Please file bug report to %s.\n",
                       queue->qid, DRV_PROJECT);
-                return -EINVAL;
+                ret = -EINVAL;
+                goto out;
         }
 
         /*
@@ -634,7 +641,8 @@ int rt2x00queue_write_tx_frame(struct data_queue *queue, struct sk_buff *skb,
         if (unlikely(rt2x00queue_write_tx_data(entry, &txdesc))) {
                 clear_bit(ENTRY_OWNER_DEVICE_DATA, &entry->flags);
                 entry->skb = NULL;
-                return -EIO;
+                ret = -EIO;
+                goto out;
         }
 
         set_bit(ENTRY_DATA_PENDING, &entry->flags);
@@ -643,7 +651,9 @@ int rt2x00queue_write_tx_frame(struct data_queue *queue, struct sk_buff *skb,
         rt2x00queue_write_tx_descriptor(entry, &txdesc);
         rt2x00queue_kick_tx_queue(queue, &txdesc);
 
-        return 0;
+out:
+        spin_unlock(&queue->tx_lock);
+        return ret;
 }
 
 int rt2x00queue_clear_beacon(struct rt2x00_dev *rt2x00dev,
@@ -1184,6 +1194,7 @@ static void rt2x00queue_init(struct rt2x00_dev *rt2x00dev,
                              struct data_queue *queue, enum data_queue_qid qid)
 {
         mutex_init(&queue->status_lock);
+        spin_lock_init(&queue->tx_lock);
         spin_lock_init(&queue->index_lock);
 
         queue->rt2x00dev = rt2x00dev;
diff --git a/drivers/net/wireless/rt2x00/rt2x00queue.h b/drivers/net/wireless/rt2x00/rt2x00queue.h
index 590047499e3c..f2100f4ddcff 100644
--- a/drivers/net/wireless/rt2x00/rt2x00queue.h
+++ b/drivers/net/wireless/rt2x00/rt2x00queue.h
@@ -432,6 +432,7 @@ enum data_queue_flags {
  * @flags: Entry flags, see &enum queue_entry_flags.
  * @status_lock: The mutex for protecting the start/stop/flush
  *      handling on this queue.
+ * @tx_lock: Spinlock to serialize tx operations on this queue.
  * @index_lock: Spinlock to protect index handling. Whenever @index, @index_done or
  *      @index_crypt needs to be changed this lock should be grabbed to prevent
  *      index corruption due to concurrency.
@@ -458,6 +459,7 @@ struct data_queue {
         unsigned long flags;
 
         struct mutex status_lock;
+        spinlock_t tx_lock;
         spinlock_t index_lock;
 
         unsigned int count;