rt2x00: Serialize TX operations on a queue.

commit 77a861c405da75d81e9e6e32c50eb7f9777777e8 upstream.

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>
Cc: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/net/wireless/rt2x00/rt2x00queue.h b/drivers/net/wireless/rt2x00/rt2x00queue.h
index 167d458..ad3d527 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;