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Subject[21/38] rt2x00: Serialize TX operations on a queue.
3.0-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Gertjan van Wingerde <gwingerde@gmail.com>

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>

---
drivers/net/wireless/rt2x00/rt2x00queue.c | 21 ++++++++++++++++-----
drivers/net/wireless/rt2x00/rt2x00queue.h | 2 ++
2 files changed, 18 insertions(+), 5 deletions(-)

--- a/drivers/net/wireless/rt2x00/rt2x00queue.c
+++ b/drivers/net/wireless/rt2x00/rt2x00queue.c
@@ -556,15 +556,21 @@ int rt2x00queue_write_tx_frame(struct da
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,
@@ -573,7 +579,8 @@ int rt2x00queue_write_tx_frame(struct da
"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;
}

/*
@@ -635,7 +642,8 @@ int rt2x00queue_write_tx_frame(struct da
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);
@@ -644,7 +652,9 @@ int rt2x00queue_write_tx_frame(struct da
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,
@@ -1185,6 +1195,7 @@ static void rt2x00queue_init(struct rt2x
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;
--- 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;



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