From: John W. Linville <linville@redhat.com>
Date: Tue, 30 Jun 2009 14:44:35 -0400
Subject: [net] rt2x00: use mac80211-provided workqueue
Message-id: 20090630184435.GL24066@redhat.com
O-Subject: [PATCH RHEL5.4] rt2x00: use mac80211-provided workqueue to avoid fatal exception
Bugzilla: 506845
RH-Acked-by: David Miller <davem@redhat.com>
RH-Acked-by: Andy Gospodarek <gospo@redhat.com>
RH-Acked-by: Stefan Assmann <sassmann@redhat.com>

QA found that pulling an rt73usb device caused a fatal exception!

BZ506845

Back-port of the following upstream commit...

commit 8e260c22238dd8b57aefb1f5e4bd114486a9c17d
Author: Ivo van Doorn <ivdoorn@gmail.com>
Date:   Fri Jul 4 13:41:31 2008 +0200

    rt2x00: Use ieee80211_hw->workqueue again

    Remove the rt2x00 singlethreaded workqueue and move
    the link tuner and packet filter scheduled work to
    the ieee80211_hw->workqueue again.
    The only exception is the interface scheduled work
    handler which uses the mac80211 interface iterator
    under the RTNL lock. This work needs to be handled
    on the kernel workqueue to prevent lockdep issues.

    Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
    Signed-off-by: John W. Linville <linville@tuxdriver.com>

Tested by Zack Cerza on 32- and 64-bit machines with acceptable results
(i.e. the panic was averted).

diff --git a/drivers/net/wireless/rt2x00/rt2x00.h b/drivers/net/wireless/rt2x00/rt2x00.h
index 631ae01..2bd9153 100644
--- a/drivers/net/wireless/rt2x00/rt2x00.h
+++ b/drivers/net/wireless/rt2x00/rt2x00.h
@@ -820,8 +820,10 @@ struct rt2x00_dev {
 
 	/*
 	 * Scheduled work.
+	 * NOTE: intf_work will use ieee80211_iterate_active_interfaces()
+	 * which means it cannot be placed on the hw->workqueue
+	 * due to RTNL locking requirements.
 	 */
-	struct workqueue_struct *workqueue;
 	struct work_struct intf_work;
 	struct work_struct filter_work;
 
diff --git a/drivers/net/wireless/rt2x00/rt2x00dev.c b/drivers/net/wireless/rt2x00/rt2x00dev.c
index a6ac62f..6ea437d 100644
--- a/drivers/net/wireless/rt2x00/rt2x00dev.c
+++ b/drivers/net/wireless/rt2x00/rt2x00dev.c
@@ -75,7 +75,7 @@ static void rt2x00lib_start_link_tuner(struct rt2x00_dev *rt2x00dev)
 
 	rt2x00lib_reset_link_tuner(rt2x00dev);
 
-	queue_delayed_work(rt2x00dev->workqueue,
+	queue_delayed_work(rt2x00dev->hw->workqueue,
 			   &rt2x00dev->link.work, LINK_TUNE_INTERVAL);
 }
 
@@ -396,7 +396,7 @@ static void rt2x00lib_link_tuner(void *r)
 	 * Increase tuner counter, and reschedule the next link tuner run.
 	 */
 	rt2x00dev->link.count++;
-	queue_delayed_work(rt2x00dev->workqueue,
+	queue_delayed_work(rt2x00dev->hw->workqueue,
 			   &rt2x00dev->link.work, LINK_TUNE_INTERVAL);
 }
 
@@ -492,7 +492,7 @@ void rt2x00lib_beacondone(struct rt2x00_dev *rt2x00dev)
 						   rt2x00lib_beacondone_iter,
 						   rt2x00dev);
 
-	queue_work(rt2x00dev->workqueue, &rt2x00dev->intf_work);
+	schedule_work(&rt2x00dev->intf_work);
 }
 EXPORT_SYMBOL_GPL(rt2x00lib_beacondone);
 
@@ -1135,10 +1135,6 @@ int rt2x00lib_probe_dev(struct rt2x00_dev *rt2x00dev)
 	/*
 	 * Initialize configuration work.
 	 */
-	rt2x00dev->workqueue = create_singlethread_workqueue("rt2x00lib");
-	if (!rt2x00dev->workqueue)
-		goto exit;
-
 	INIT_WORK(&rt2x00dev->intf_work, rt2x00lib_intf_scheduled, rt2x00dev);
 	INIT_WORK(&rt2x00dev->filter_work, rt2x00lib_packetfilter_scheduled,
 		  rt2x00dev);
@@ -1200,15 +1196,6 @@ void rt2x00lib_remove_dev(struct rt2x00_dev *rt2x00dev)
 	rt2x00leds_unregister(rt2x00dev);
 
 	/*
-	 * Stop all queued work. Note that most tasks will already be halted
-	 * during rt2x00lib_disable_radio() and rt2x00lib_uninitialize().
-	 */
-	if (rt2x00dev->workqueue) {
-		flush_workqueue(rt2x00dev->workqueue);
-		destroy_workqueue(rt2x00dev->workqueue);
-	}
-
-	/*
 	 * Free ieee80211_hw memory.
 	 */
 	rt2x00lib_remove_hw(rt2x00dev);
diff --git a/drivers/net/wireless/rt2x00/rt2x00mac.c b/drivers/net/wireless/rt2x00/rt2x00mac.c
index 9cb023e..802ddba 100644
--- a/drivers/net/wireless/rt2x00/rt2x00mac.c
+++ b/drivers/net/wireless/rt2x00/rt2x00mac.c
@@ -428,7 +428,7 @@ void rt2x00mac_configure_filter(struct ieee80211_hw *hw,
 	if (!test_bit(DRIVER_REQUIRE_SCHEDULED, &rt2x00dev->flags))
 		rt2x00dev->ops->lib->config_filter(rt2x00dev, *total_flags);
 	else
-		queue_work(rt2x00dev->workqueue, &rt2x00dev->filter_work);
+		queue_work(rt2x00dev->hw->workqueue, &rt2x00dev->filter_work);
 }
 EXPORT_SYMBOL_GPL(rt2x00mac_configure_filter);
 
@@ -509,7 +509,7 @@ void rt2x00mac_bss_info_changed(struct ieee80211_hw *hw,
 	memcpy(&intf->conf, bss_conf, sizeof(*bss_conf));
 	if (delayed) {
 		intf->delayed_flags |= delayed;
-		queue_work(rt2x00dev->workqueue, &rt2x00dev->intf_work);
+		schedule_work(&rt2x00dev->intf_work);
 	}
 	spin_unlock(&intf->lock);
 }