mwifiex: fix race when queuing commands

Running the following script repeatedly on XO-4 with SD8787
produces command timeout and system lockup.

insmod mwifiex_sdio.ko
sleep 1
ifconfig eth0 up
iwlist eth0 scan &
sleep 0.5
rmmod mwifiex_sdio

mwifiex_send_cmd_async() is called for sync as well as async
commands. (mwifiex_send_cmd_sync() internally calls it for
sync command.)

"adapter->cmd_queued" gets filled inside mwifiex_send_cmd_async()
routine for both types of commands. But it is used only for sync
commands in mwifiex_wait_queue_complete(). This could lead to a
race when two threads try to queue a sync command with another
sync/async command simultaneously.

Get rid of global variable and pass command node as a parameter
to mwifiex_wait_queue_complete() to fix the problem.

Cc: <stable@vger.kernel.org> # 3.8
Reported-by: Daniel Drake <dsd@laptop.org>
Tested-by: Daniel Drake <dsd@laptop.org>
Tested-by: Marco Cesarano <marco@marvell.com>
Signed-off-by: Amitkumar Karwar <akarwar@marvell.com>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 4 insertions, 4 deletions

diff --git a/drivers/net/wireless/mwifiex/scan.c b/drivers/net/wireless/mwifiex/scan.c
index bb60c2754a97..d215b4d3c51b 100644
--- a/drivers/net/wireless/mwifiex/scan.c
+++ b/drivers/net/wireless/mwifiex/scan.c
@@ -1388,10 +1388,13 @@ int mwifiex_scan_networks(struct mwifiex_private *priv,
                         list_del(&cmd_node->list);
                         spin_unlock_irqrestore(&adapter->scan_pending_q_lock,
                                                flags);
-                        adapter->cmd_queued = cmd_node;
                         mwifiex_insert_cmd_to_pending_q(adapter, cmd_node,
                                                         true);
                         queue_work(adapter->workqueue, &adapter->main_work);
+
+                        /* Perform internal scan synchronously */
+                        if (!priv->scan_request)
+                                mwifiex_wait_queue_complete(adapter, cmd_node);
                 } else {
                         spin_unlock_irqrestore(&adapter->scan_pending_q_lock,
                                                flags);
@@ -1946,9 +1949,6 @@ int mwifiex_request_scan(struct mwifiex_private *priv,
                 /* Normal scan */
                 ret = mwifiex_scan_networks(priv, NULL);
 
-        if (!ret)
-                ret = mwifiex_wait_queue_complete(priv->adapter);
-
         up(&priv->async_sem);
 
         return ret;