libertas: fix cmdpendingq locking

We occasionally see list corruption using libertas.

While we haven't been able to diagnose this precisely, we have spotted
a possible cause: cmdpendingq is generally modified with driver_lock
held. However, there are a couple of points where this is not the case.

Fix up those operations to execute under the lock, it seems like
the correct thing to do and will hopefully improve the situation.
Signed-off-by: NPaul Fox <pgf@laptop.org>
Signed-off-by: NDaniel Drake <dsd@laptop.org>
Acked-by: NDan Williams <dcbw@redhat.com>
Cc: stable@kernel.org
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

drivers/net/wireless/libertas/cmd.c

@@ -1339,8 +1339,8 @@ int lbs_execute_next_command(struct lbs_private *priv)
 				    cpu_to_le16(PS_MODE_ACTION_EXIT_PS)) {
 					lbs_deb_host(
 					       "EXEC_NEXT_CMD: ignore ENTER_PS cmd\n");
-					list_del(&cmdnode->list);
 					spin_lock_irqsave(&priv->driver_lock, flags);
+					list_del(&cmdnode->list);
 					lbs_complete_command(priv, cmdnode, 0);
 					spin_unlock_irqrestore(&priv->driver_lock, flags);
 
@@ -1352,8 +1352,8 @@ int lbs_execute_next_command(struct lbs_private *priv)
 				    (priv->psstate == PS_STATE_PRE_SLEEP)) {
 					lbs_deb_host(
 					       "EXEC_NEXT_CMD: ignore EXIT_PS cmd in sleep\n");
-					list_del(&cmdnode->list);
 					spin_lock_irqsave(&priv->driver_lock, flags);
+					list_del(&cmdnode->list);
 					lbs_complete_command(priv, cmdnode, 0);
 					spin_unlock_irqrestore(&priv->driver_lock, flags);
 					priv->needtowakeup = 1;
@@ -1366,7 +1366,9 @@ int lbs_execute_next_command(struct lbs_private *priv)
 				       "EXEC_NEXT_CMD: sending EXIT_PS\n");
 			}
 		}
+		spin_lock_irqsave(&priv->driver_lock, flags);
 		list_del(&cmdnode->list);
+		spin_unlock_irqrestore(&priv->driver_lock, flags);
 		lbs_deb_host("EXEC_NEXT_CMD: sending command 0x%04x\n",
 			    le16_to_cpu(cmd->command));
 		lbs_submit_command(priv, cmdnode);