linux-kernel - [PATCH] rt2x00: Fix lockdep warning in rt2x00lib_probe

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Date:	Fri, 16 Jul 2010 09:50:10 -0700
From:	Stephen Boyd <bebarino@...il.com>
To:	users@...x00.serialmonkey.com
Cc:	Ivo van Doorn <IvDoorn@...il.com>,
	"John W. Linville" <linville@...driver.com>,
	linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] rt2x00: Fix lockdep warning in rt2x00lib_probe_dev()

The rt2x00dev->intf_work workqueue is never initialized when a driver is
probed for a non-existent device (in this case rt2500usb). On such a
path we call rt2x00lib_remove_dev() to free any resources initialized
during the probe before we use INIT_WORK to initialize the workqueue.
This causes lockdep to get confused since the lock used in the workqueue
hasn't been initialized yet but is now being acquired during
cancel_work_sync() called by rt2x00lib_remove_dev().

Fix this by initializing the workqueue first before we attempt to probe
the device. This should make lockdep happy and avoid breaking any
assumptions about how the library cleans up after a probe fails.

phy0 -> rt2x00lib_probe_dev: Error - Failed to allocate device.
INFO: trying to register non-static key.
the code is fine but needs lockdep annotation.
turning off the locking correctness validator.
Pid: 2027, comm: modprobe Not tainted 2.6.35-rc5+ #60
Call Trace:
 [<ffffffff8105fe59>] register_lock_class+0x152/0x31f
 [<ffffffff81344a00>] ? usb_control_msg+0xd5/0x111
 [<ffffffff81061bde>] __lock_acquire+0xce/0xcf4
 [<ffffffff8105f6fd>] ? trace_hardirqs_off+0xd/0xf
 [<ffffffff81492aef>] ?  _raw_spin_unlock_irqrestore+0x33/0x41
 [<ffffffff810628d5>] lock_acquire+0xd1/0xf7
 [<ffffffff8104f037>] ? __cancel_work_timer+0x99/0x17e
 [<ffffffff8104f06e>] __cancel_work_timer+0xd0/0x17e
 [<ffffffff8104f037>] ? __cancel_work_timer+0x99/0x17e
 [<ffffffff8104f136>] cancel_work_sync+0xb/0xd
 [<ffffffffa0096675>] rt2x00lib_remove_dev+0x25/0xb0 [rt2x00lib]
 [<ffffffffa0096bf7>] rt2x00lib_probe_dev+0x380/0x3ed [rt2x00lib]
 [<ffffffff811d78a7>] ? __raw_spin_lock_init+0x31/0x52
 [<ffffffffa00bbd2c>] ? T.676+0xe/0x10 [rt2x00usb]
 [<ffffffffa00bbe4f>] rt2x00usb_probe+0x121/0x15e [rt2x00usb]
 [<ffffffff813468bd>] usb_probe_interface+0x151/0x19e
 [<ffffffff812ea08e>] driver_probe_device+0xa7/0x136
 [<ffffffff812ea167>] __driver_attach+0x4a/0x66
 [<ffffffff812ea11d>] ? __driver_attach+0x0/0x66
 [<ffffffff812e96ca>] bus_for_each_dev+0x54/0x89
 [<ffffffff812e9efd>] driver_attach+0x19/0x1b
 [<ffffffff812e9b64>] bus_add_driver+0xb4/0x204
 [<ffffffff812ea41b>] driver_register+0x98/0x109
 [<ffffffff813465dd>] usb_register_driver+0xb2/0x173
 [<ffffffffa00ca000>] ? rt2500usb_init+0x0/0x20 [rt2500usb]
 [<ffffffffa00ca01e>] rt2500usb_init+0x1e/0x20 [rt2500usb]
 [<ffffffff81000203>] do_one_initcall+0x6d/0x17a
 [<ffffffff8106cae8>] sys_init_module+0x9c/0x1e0
 [<ffffffff8100296b>] system_call_fastpath+0x16/0x1b

Signed-off-by: Stephen Boyd <bebarino@...il.com>
---
 drivers/net/wireless/rt2x00/rt2x00dev.c |   10 +++++-----
 1 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/net/wireless/rt2x00/rt2x00dev.c b/drivers/net/wireless/rt2x00/rt2x00dev.c
index 3ae468c..f20d3ee 100644
--- a/drivers/net/wireless/rt2x00/rt2x00dev.c
+++ b/drivers/net/wireless/rt2x00/rt2x00dev.c
@@ -854,6 +854,11 @@ int rt2x00lib_probe_dev(struct rt2x00_dev *rt2x00dev)
 		    BIT(NL80211_IFTYPE_WDS);
 
 	/*
+	 * Initialize configuration work.
+	 */
+	INIT_WORK(&rt2x00dev->intf_work, rt2x00lib_intf_scheduled);
+
+	/*
 	 * Let the driver probe the device to detect the capabilities.
 	 */
 	retval = rt2x00dev->ops->lib->probe_hw(rt2x00dev);
@@ -863,11 +868,6 @@ int rt2x00lib_probe_dev(struct rt2x00_dev *rt2x00dev)
 	}
 
 	/*
-	 * Initialize configuration work.
-	 */
-	INIT_WORK(&rt2x00dev->intf_work, rt2x00lib_intf_scheduled);
-
-	/*
 	 * Allocate queue array.
 	 */
 	retval = rt2x00queue_allocate(rt2x00dev);
-- 
1.7.2.rc2.10.g637ab

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