Kernel oop when accessing vloopback device

Question

When I first built the vloopback module, and modprobed it, I used it successfully for several hours. However, upon rebooting my machine, I can still load it, but whenever either Xawtv or WebCamStudio accesses the device, it kernel oops. I have not tried accessing it with Motion.

It does this regardless of whether there is a webcam attached or not, so it's not the webcam driver.

I'm running Fedora 8 with a 2.6.29.6 kernel. I also tried with an older kernel, 2.6.26.8-57.fc8 with the same results. I have 1GB RAM and a dual core athlon64 CPU.

EDIT: Found the problem Apparently my multiple source directories of both v4l-dvb and vloopback(1.1, 1.2, trunk) were getting confused in the linking process. I would build from the 1.2 directory, but when I would modprobe the vloopback device, it would load v1.3trunk, and link to the wrong v4l-dvb sources....or vise versa.

Deleting the extra source trees, rebuilding my kernel modules, then rebuilding v1.3trunk, and the latest v4l-dvb did the trick. Whew, seven days to get it right. Thanks for your help.

Message from syslogd@garage at Aug  2 15:53:31 ...
 kernel: Oops: 0000 [#1] SMP 

Message from syslogd@garage at Aug  2 15:53:31 ...
 kernel: last sysfs file: /sys/class/video4linux/video1/dev

Message from syslogd@garage at Aug  2 15:53:31 ...
 kernel: Stack:

Message from syslogd@garage at Aug  2 15:53:31 ...
 kernel:  c0491006 f4429e80 f4429e00 00000022 f45c5fb0 c0491f6a f451a480 00000022

Message from syslogd@garage at Aug  2 15:53:31 ...
 kernel:  00000000 9028a400 f45c5000 c040385b 00000022 00000000 8feb4234 00000000

Message from syslogd@garage at Aug  2 15:53:31 ...
 kernel: Call Trace:

Message from syslogd@garage at Aug  2 15:53:31 ...
 kernel:  [<c04939e6>] ? fput+0x17/0x19

Message from syslogd@garage at Aug  2 15:53:31 ...
 kernel:  [<c0491006>] ? filp_close+0x51/0x5b

Message from syslogd@garage at Aug  2 15:53:31 ...
 kernel: Process java (pid: 3400, ti=f45c5000 task=f4564920 task.ti=f45c5000)

Message from syslogd@garage at Aug  2 15:53:31 ...
 kernel:  [<c0491f6a>] ? sys_close+0x74/0xa9

Message from syslogd@garage at Aug  2 15:53:31 ...
 kernel:  [<c040385b>] ? sysenter_do_call+0x12/0x2f

Message from syslogd@garage at Aug  2 15:53:31 ...
 kernel: Code: 70 70 6c 69 63 61 74 69 6f 6e 2d 70 64 66 2e 6d 6e 67 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 <02> 00 00 00 00 00 00 00 08 08 00 00 00 00 00 00 e0 51 28 f6 00 

Message from syslogd@garage at Aug  2 15:53:31 ...
 kernel: EIP: [<eaa3d110>] 0xeaa3d110 SS:ESP 0068:f45c5f68



And the output from dmesg:
Linux video capture interface: v2.00
[vloopback_init] : video4linux loopback driver v1.3-trunk
[vloopback_init] : Loopback 0 registered, input: video0, output: video1
[vloopback_init] : Loopback 0 , Using 2 buffers
------------[ cut here ]------------
WARNING: at mm/vmalloc.c:1207 __vunmap+0x42/0x8e()
Hardware name:
Trying to vfree() bad address (f451a480)
Modules linked in: vloopback videodev v4l1_compat nls_utf8 cifs autofs4 nfs lockd nfs_acl auth_rpcgss rfcomm l2cap bluetooth sunrpc cpufreq_ondemand powernow_k8 dm_mirror dm_region_hash dm_log dm_multipath dm_mod ipv6 snd_intel8x0 snd_seq_dummy snd_ice1712 snd_seq_oss snd_ice17xx_ak4xxx snd_ak4xxx_adda snd_seq_midi_event snd_cs8427 snd_seq snd_ac97_codec snd_pcm_oss ac97_bus snd_i2c snd_mixer_oss nvidia(P) snd_mpu401_uart snd_pcm snd_rawmidi snd_seq_device snd_timer tg3 snd libphy i2c_nforce2 soundcore k8temp sr_mod i2c_core snd_page_alloc pcspkr hwmon cdrom sg pata_amd ata_generic sata_nv pata_acpi libata sd_mod scsi_mod ext3 jbd mbcache uhci_hcd ohci_hcd ehci_hcd [last unloaded: scsi_wait_scan]
Pid: 3400, comm: java Tainted: P           2.6.29.6 #1
Call Trace:
 [<c042b399>] warn_slowpath+0x74/0x8a
 [<c0423e97>] ? try_to_wake_up+0x236/0x241
 [<c0423ead>] ? default_wake_function+0xb/0xd
 [<c041f475>] ? __wake_up_common+0x2f/0x5a
 [<c0420739>] ? __wake_up+0x31/0x3b
 [<c0446d03>] ? wake_futex+0x22/0x2f
 [<c0447eac>] ? do_futex+0x3ec/0x7a6
 [<c0413a04>] ? lapic_next_event+0x13/0x17
 [<c0444665>] ? clockevents_program_event+0xdb/0xea
 [<c0485f52>] __vunmap+0x42/0x8e
 [<c0485fe7>] vfree+0x25/0x27
 [<f7d98035>] rvfree+0x35/0x3a [vloopback]
 [<f7dba5b0>] ? v4l2_release+0x26/0x33 [videodev]
 [<c0493636>] __fput+0xc9/0x179
 [<c04939e6>] fput+0x17/0x19
 [<c0491006>] filp_close+0x51/0x5b
 [<c0491f6a>] sys_close+0x74/0xa9
 [<c040385b>] sysenter_do_call+0x12/0x2f
---[ end trace f363257d7b0082d4 ]---
BUG: unable to handle kernel NULL pointer dereference at 00000009
IP: [<eaa3d110>] 0xeaa3d110
*pde = 00000000
Oops: 0000 [#1] SMP
last sysfs file: /sys/class/video4linux/video1/dev
Modules linked in: vloopback videodev v4l1_compat nls_utf8 cifs autofs4 nfs lockd nfs_acl auth_rpcgss rfcomm l2cap bluetooth sunrpc cpufreq_ondemand powernow_k8 dm_mirror dm_region_hash dm_log dm_multipath dm_mod ipv6 snd_intel8x0 snd_seq_dummy snd_ice1712 snd_seq_oss snd_ice17xx_ak4xxx snd_ak4xxx_adda snd_seq_midi_event snd_cs8427 snd_seq snd_ac97_codec snd_pcm_oss ac97_bus snd_i2c snd_mixer_oss nvidia(P) snd_mpu401_uart snd_pcm snd_rawmidi snd_seq_device snd_timer tg3 snd libphy i2c_nforce2 soundcore k8temp sr_mod i2c_core snd_page_alloc pcspkr hwmon cdrom sg pata_amd ata_generic sata_nv pata_acpi libata sd_mod scsi_mod ext3 jbd mbcache uhci_hcd ohci_hcd ehci_hcd [last unloaded: scsi_wait_scan]

Pid: 3400, comm: java Tainted: P        W  (2.6.29.6 #1)
EIP: 0060:[<eaa3d110>] EFLAGS: 00010282 CPU: 1
EIP is at 0xeaa3d110
EAX: 00000009 EBX: f7dba5b0 ECX: c078b6a4 EDX: 00fc6000
ESI: 00000008 EDI: f45c5f7c EBP: c0493636 ESP: f45c5f68
 DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
Process java (pid: 3400, ti=f45c5000 task=f4564920 task.ti=f45c5000)
Stack:
 f6726380 f62851e0 f451a480 f4429e00 00000000 f45c5f84 c04939e6 f45c5f98
 c0491006 f4429e80 f4429e00 00000022 f45c5fb0 c0491f6a f451a480 00000022
 00000000 9028a400 f45c5000 c040385b 00000022 00000000 8feb4234 00000000
Call Trace:
 [<c04939e6>] ? fput+0x17/0x19
 [<c0491006>] ? filp_close+0x51/0x5b
 [<c0491f6a>] ? sys_close+0x74/0xa9
 [<c040385b>] ? sysenter_do_call+0x12/0x2f
Code: 70 70 6c 69 63 61 74 69 6f 6e 2d 70 64 66 2e 6d 6e 67 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 <02> 00 00 00 00 00 00 00 08 08 00 00 00 00 00 00 e0 51 28 f6 00
EIP: [<eaa3d110>] 0xeaa3d110 SS:ESP 0068:f45c5f68
---[ end trace f363257d7b0082d5 ]---

Environment

Motion version:	3.2.11
ffmpeg version:
Libraries:	ffmpeg, mysql, postgresql
Server OS:

-- JimHines - 02 Aug 2009

Follow Up

Jim , please give a try with motion.

Also could be helpfull some information about the driver of webcam you are using.

-- AngelCarpintero - 03 Aug 2009

Answer

Ok

-- AngelCarpintero - 08 Aug 2009