Manoj -
On Wed, 25 Apr 2012, Andrei Emeltchenko wrote:
Hi Manoj,
On Wed, Apr 25, 2012 at 01:59:03PM +0530, Manoj wrote:
While running in L2CAP ERTM mode, sometimes ERTM packet queue
gets corrupted because though method l2cap_ertm_send() is not
thread-safe, it is called simultaneously from multiple
threads.
Could you give examples how queue is corrupted?
Best regards
Andrei Emeltchenko
Around the time that bluetooth-next made the switch to workqueues, I
saw some issues where the packet sent in l2cap_ertm_send could be
acked in tasklet context before l2cap_ertm_send finished running.
This would cause the packet to be removed from the tx_q before
skb_queue_is_last() was called, which would in turn result in a
corrupt tx_send_head pointer.
With workqueues and proper locking, this should not be a problem.
The lock that needs to be held when changing tx_q is acquired using
l2cap_chan_lock(), *not* the mutex_lock() used in this patch. Callers
of l2cap_ertm_send() should already hold l2cap_chan_lock(), which will
provide thread safety. It looks like l2cap_chan_lock() is not held
when l2cap_ertm_send() is called by l2cap_chan_send().
(Also keep in mind that l2cap_chan_lock() cannot be held when
l2cap_create_iframe_pdu() is called, because it's possible to block
while allocating iframe skbs)
Signed-off-by: Manoj <manojkr.sharma@xxxxxxxxxxxxxx>
---
net/bluetooth/l2cap_core.c | 3 ++-
1 files changed, 2 insertions(+), 1 deletions(-)
diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index 19807c9..a9319e2 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -1713,6 +1713,7 @@ static int l2cap_ertm_send(struct l2cap_chan *chan)
if (chan->state != BT_CONNECTED)
return -ENOTCONN;
+ mutex_lock(&chan->conn->chan_lock);
while ((skb = chan->tx_send_head) && (!l2cap_tx_window_full(chan))) {
if (chan->remote_max_tx &&
@@ -1765,7 +1766,7 @@ static int l2cap_ertm_send(struct l2cap_chan *chan)
else
chan->tx_send_head = skb_queue_next(&chan->tx_q, skb);
}
-
+ mutex_unlock(&chan->conn->chan_lock);
return nsent;
}
--
1.6.6.1
Regards,
--
Mat Martineau
Employee of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum
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