Problem with sn9c102 webcam locks ..

["alpha @ steudten Engineering" <alpha@steudten.com>]

Hi list

unplugging the webcam, the kernel 2.6.18 gives this output..

description:    V4L2 driver for SN9C10x PC Camera Controllers
version:        1:1.27
license:        GPL
vermagic:       2.6.18-1.2200self mod_unload PENTIUMM REGPARM gcc-4.1
depends:        videodev,v4l2-common


usb 2-2: new full speed USB device using uhci_hcd and address 2
PM: Adding info for usb:2-2
PM: Adding info for No Bus:usbdev2.2_ep00
usb 2-2: configuration #1 chosen from 1 choice
PM: Adding info for usb:2-2:1.0
PM: Adding info for No Bus:usbdev2.2_ep81
PM: Adding info for No Bus:usbdev2.2_ep82
PM: Adding info for No Bus:usbdev2.2_ep83
Linux video capture interface: v2.00
sn9c102: V4L2 driver for SN9C10x PC Camera Controllers v1:1.27
usb 2-2: SN9C10[12] PC Camera Controller detected (vid/pid 0x0C45/0x6029)
usb 2-2: PAS106B image sensor detected
usb 2-2: Initialization succeeded
usb 2-2: V4L2 device registered as /dev/video0
usbcore: registered new driver sn9c102

=======================================================
[ INFO: possible circular locking dependency detected ]
2.6.18-1.2200self #1
-------------------------------------------------------
sn-webcam/3184 is trying to acquire lock:
 (&cam->dev_mutex){--..}, at: [<c03261e6>] mutex_lock_interruptible+0x21/0x24

but task is already holding lock:
 (videodev_lock){--..}, at: [<c0326512>] mutex_lock+0x21/0x24

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (videodev_lock){--..}:
       [<c012da43>] __lock_acquire+0x82c/0x904
       [<c012e083>] lock_acquire+0x4b/0x6c
       [<c03263a4>] __mutex_lock_slowpath+0xb3/0x200
       [<c0326512>] mutex_lock+0x21/0x24
       [<f93f91a2>] video_register_device+0x9e/0x217 [videodev]
       [<f9c76f42>] sn9c102_usb_probe+0x36e/0x4f2 [sn9c102]
       [<c02a0bbc>] usb_probe_interface+0x5b/0x8b
       [<c0267866>] driver_probe_device+0x45/0x92
       [<c026798f>] __driver_attach+0x66/0x8f
       [<c02672e5>] bus_for_each_dev+0x36/0x5b
       [<c02677c1>] driver_attach+0x14/0x17
       [<c0266fc5>] bus_add_driver+0x68/0x106
       [<c0267c2f>] driver_register+0x78/0x7d
       [<c02a09dd>] usb_register_driver+0x65/0xc6
       [<f9396028>] 0xf9396028
       [<c01341a1>] sys_init_module+0x1340/0x148b
       [<c0102e17>] syscall_call+0x7/0xb
       [<ffffffff>] 0xffffffff

-> #0 (&cam->dev_mutex){--..}:
       [<c012d977>] __lock_acquire+0x760/0x904
       [<c012e083>] lock_acquire+0x4b/0x6c
       [<c0326024>] __mutex_lock_interruptible_slowpath+0xb3/0x254
       [<c03261e6>] mutex_lock_interruptible+0x21/0x24
       [<f9c766d9>] sn9c102_open+0x43/0x53e [sn9c102]
       [<f93fb2e2>] video_open+0xba/0x135 [videodev]
       [<c0167125>] chrdev_open+0xf3/0x123
       [<c015e2ae>] __dentry_open+0xb9/0x187
       [<c015e3ea>] nameidata_to_filp+0x1c/0x2e
       [<c015e42a>] do_filp_open+0x2e/0x35
       [<c015e471>] do_sys_open+0x40/0xb5
       [<c015e512>] sys_open+0x16/0x18
       [<c0102e17>] syscall_call+0x7/0xb
       [<ffffffff>] 0xffffffff

other info that might help us debug this:

2 locks held by sn-webcam/3184:
 #0:  (videodev_lock){--..}, at: [<c0326512>] mutex_lock+0x21/0x24
 #1:  (sn9c102_disconnect){..--}, at: [<f9c766b1>] sn9c102_open+0x1b/0x53e [sn9c102]

stack backtrace:
 [<c0103c87>] show_trace_log_lvl+0x12/0x25
 [<c0103d6a>] show_trace+0xd/0x10
 [<c0104532>] dump_stack+0x19/0x1b
 [<c012d20c>] print_circular_bug_tail+0x59/0x64
 [<c012d977>] __lock_acquire+0x760/0x904
 [<c012e083>] lock_acquire+0x4b/0x6c
 [<c0326024>] __mutex_lock_interruptible_slowpath+0xb3/0x254
 [<c03261e6>] mutex_lock_interruptible+0x21/0x24
 [<f9c766d9>] sn9c102_open+0x43/0x53e [sn9c102]
 [<f93fb2e2>] video_open+0xba/0x135 [videodev]
 [<c0167125>] chrdev_open+0xf3/0x123
 [<c015e2ae>] __dentry_open+0xb9/0x187
 [<c015e3ea>] nameidata_to_filp+0x1c/0x2e
 [<c015e42a>] do_filp_open+0x2e/0x35
 [<c015e471>] do_sys_open+0x40/0xb5
 [<c015e512>] sys_open+0x16/0x18
 [<c0102e17>] syscall_call+0x7/0xb
 =======================
usb 2-2: USB disconnect, address 2
PM: Removing info for No Bus:usbdev2.2_ep81
PM: Removing info for No Bus:usbdev2.2_ep82
PM: Removing info for No Bus:usbdev2.2_ep83
usb 2-2: Disconnecting SN9C10x PC Camera...
usb 2-2: V4L2 device /dev/video0 deregistered
PM: Removing info for usb:2-2:1.0
PM: Removing info for No Bus:usbdev2.2_ep00
PM: Removing info for usb:2-2
Slab corruption: (Not tainted) start=e6fd417c, len=1024
Redzone: 0x5a2cf071/0x5a2cf071.
Last user: [<c029a4c2>](usb_release_dev+0x40/0x43)
 [<c0103c87>] show_trace_log_lvl+0x12/0x25
 [<c0103d6a>] show_trace+0xd/0x10
 [<c0104532>] dump_stack+0x19/0x1b
 [<c015b3a1>] check_poison_obj+0x6f/0x171
 [<c015b4c8>] cache_alloc_debugcheck_after+0x25/0x135
 [<c015c682>] kmem_cache_alloc+0x94/0xa0
 [<c013f051>] audit_alloc+0x65/0xc4
 [<c01161e2>] copy_process+0x56e/0x11a6
 [<c0116e5c>] do_fork+0x42/0x112
 [<c0101200>] sys_clone+0x25/0x2a
 [<c0102e17>] syscall_call+0x7/0xb
 =======================
170: 6b 6b 6b 6b 6b 6b 6b 6b 6a 6b 6b 6b 6b 6b 6b 6b
Single bit error detected. Probably bad RAM.
Run memtest86+ or a similar memory test tool.
Next obj: start=e6fd4588, len=1024
Redzone: 0x5a2cf071/0x5a2cf071.
Last user: [<c02cea08>](skb_release_data+0x80/0x84)
000: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
010: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b

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