mwifiex: handle race during mwifiex_usb_disconnect

Race condition is observed during rmmod of mwifiex_usb:

1. The rmmod thread will call mwifiex_usb_disconnect(), download
   SHUTDOWN command and do wait_event_interruptible_timeout(),
   waiting for response.

2. The main thread will handle the response and will do a
   wake_up_interruptible(), unblocking rmmod thread.

3. On getting unblocked, rmmod thread  will make rx_cmd.urb = NULL in
   mwifiex_usb_free().

4. The main thread will try to resubmit rx_cmd.urb in
   mwifiex_usb_submit_rx_urb(), which is NULL.

To fix this, move mwifiex_usb_free() from mwifiex_usb_disconnect
to mwifiex_unregister_dev(). Function mwifiex_unregister_dev() is
called after flushing the command and RX work queues.

Suggested-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Ganapathi Bhat <gbhat@marvell.com>
Reviewed-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

diff --git a/drivers/net/wireless/marvell/mwifiex/usb.c b/drivers/net/wireless/marvell/mwifiex/usb.c
index bc475b8..88f4c89 100644 (file)
--- a/drivers/net/wireless/marvell/mwifiex/usb.c
+++ b/drivers/net/wireless/marvell/mwifiex/usb.c
@@ -644,8 +644,6 @@ static void mwifiex_usb_disconnect(struct usb_interface *intf)
                                         MWIFIEX_FUNC_SHUTDOWN);
        }
 
-       mwifiex_usb_free(card);
-
        mwifiex_dbg(adapter, FATAL,
                    "%s: removing card\n", __func__);
        mwifiex_remove_card(adapter);
@@ -1353,6 +1351,8 @@ static void mwifiex_unregister_dev(struct mwifiex_adapter *adapter)
 {
        struct usb_card_rec *card = (struct usb_card_rec *)adapter->card;
 
+       mwifiex_usb_free(card);
+
        mwifiex_usb_cleanup_tx_aggr(adapter);
 
        card->adapter = NULL;