Hi
Yes. I will try it out and post a message as soon as I have some
experience with it.
Regards
Rune
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Rune Sætre <rune.saetre@xxxxxxxxxxx>
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On Wed, 19 Jan 2011, Patrik Jakobsson wrote:
On 01/18/2011 05:30 PM, Hans Verkuil wrote:
On Tuesday, January 18, 2011 17:14:03 Patrik Jakobsson wrote:
Hello Rune
I'm trying to learn more about the linux kernel so I figured helping
with bugs is a good way to get started.
On 01/18/2011 02:20 AM, Rune Saetre wrote:
Hi
The crash is not as consistent as I first believed. I have managed to
stop and start capturing several (but not many) times without the
driver crashing now.
To me it seems that the resource locking (functions res_get, res_check,
res_locked and res_free) is subject to race condition.
I looked at older versions of the code and found that there used to be
locks around some of these pieces. It was removed in commit:
0499a5aa777f8e56e46df362f0bb9d9d116186f9 - V4L/DVB: em28xx: remove BKL
Other V4L drivers use pretty much the same code (res_get, res_free,
etc.) for resource locking but still have the mutex_lock/unlock around
it. Does anyone know why this was removed?
Because now the video4linux core does the locking.
Anyway, I'm pretty sure this is the bug that was fixed here:
http://www.mail-archive.com/linuxtv-commits@xxxxxxxxxxx/msg09413.html
This fix will be in 2.6.38.
The change in the locking mechanism had nothing to do this particular bug.
It was just incorrect administration of resources.
Regards,
Hans
Thanks for the explanation. I see now how the V4L core locks around the
ioctls. The member unlocked_ioctl of struct v4l2_file_operations confused me
a little. Maybe serialized_ioctl would be a better name? Not a big issue
though.
Hopefully the patch fixes your problem Rune.
Thanks
Patrik Jakobsson
Thanks
Patrik Jakobsson
The trace logs also differ slightly. Here is the last one:
Jan 18 02:12:08 mate kernel: [ 117.219326] ------------[ cut here
]------------
Jan 18 02:12:08 mate kernel: [ 117.219412] kernel BUG at
drivers/media/video/em28xx/em28xx-video.c:891!
Jan 18 02:12:08 mate kernel: [ 117.219507] invalid opcode: 0000 [#1]
PREEMPT SMP Jan 18 02:12:08 mate kernel: [ 117.219597] last sysfs
file: /sys/devices/virtual/block/dm-8/stat
Jan 18 02:12:08 mate kernel: [ 117.219681] CPU 1 Jan 18 02:12:08 mate
kernel: [ 117.219714] Modules linked in: acpi_cpufreq mperf
cpufreq_powersave cpufreq_stats cpufreq_userspace cpufreq_conservative
ppdev lp nfsd lockd nfs_acl auth_rpcgss sunrpc exportfs binfmt_misc
fuse dummy bridge stp ext2 mbcache coretemp kvm_intel kvm loop
firewire_sbp2 tuner snd_hda_codec_realtek arc4 snd_hda_intel
snd_usb_audio snd_hda_codec ecb snd_seq_dummy snd_pcm_oss
snd_mixer_oss saa7115 snd_pcm ir_lirc_codec lirc_dev ir_sony_decoder
snd_hwdep snd_usbmidi_lib em28xx ir_jvc_decoder ir_rc6_decoder
snd_seq_oss snd_seq_midi snd_rawmidi r8169 ir_rc5_decoder mii
ir_nec_decoder snd_seq_midi_event i915 v4l2_common iwlagn iwlcore
snd_seq ir_core drm_kms_helper drm videobuf_vmalloc snd_timer
snd_seq_device videobuf_core pcmcia joydev mac80211 uvcvideo videodev
v4l1_compat v4l2_compat_ioctl32 tveeprom cfg80211 rfkill i2c_i801
i2c_algo_bit tpm_tis tpm yenta_socket snd intel_agp shpchp pci_hotplug
video output pcmcia_rsrc wmi pcmcia_core soundcore snd_page_alloc
parport_pc parport i2c_cor
Jan 18 02:12:08 mate kernel: irda tpm_bios intel_gtt pcspkr crc_ccitt
psmouse evdev serio_raw container processor battery ac button reiserfs
dm_mod raid10 raid456 async_raid6_recov async_pq raid6_pq async_xor
xor async_memcpy async_tx raid1 raid0 multipath linear md_mod
ide_cd_mod cdrom sd_mod ata_generic pata_acpi ata_piix crc_t10dif
ide_pci_generic ahci libahci sdhci_pci firewire_ohci sdhci libata
scsi_mod piix ide_core firewire_core mmc_core uhci_hcd tg3 thermal
crc_itu_t thermal_sys ehci_hcd [last unloaded: scsi_wait_scan]
Jan 18 02:12:08 mate kernel: [ 117.220091] Jan 18 02:12:08 mate
kernel: [ 117.220091] Pid: 3154, comm: camera_factory_ Not tainted
2.6.37-rst #1 Victoria /TravelMate 6292 Jan 18 02:12:08 mate
kernel: [ 117.220091] RIP: 0010:[<ffffffffa05a37f4>]
[<ffffffffa05a37f4>] res_free+0x14/0x49 [em28xx]
Jan 18 02:12:08 mate kernel: [ 117.220091] RSP:
0018:ffff8800794a1c48 EFLAGS: 00010297
Jan 18 02:12:08 mate kernel: [ 117.220091] RAX: 0000000000000001 RBX:
ffff88007b94dc00 RCX: 0000000000000000
Jan 18 02:12:08 mate kernel: [ 117.220091] RDX: 0000000000000000 RSI:
ffff8800378e7000 RDI: ffff88007b94dc00
Jan 18 02:12:09 mate kernel: [ 117.220091] RBP: ffff8800378e7000 R08:
0000000000000001 R09: 0000000000000c52
Jan 18 02:12:09 mate kernel: [ 117.220091] R10: 0000000000000000 R11:
0000000000000246 R12: 0000000000000000
Jan 18 02:12:09 mate kernel: [ 117.220091] R13: ffffffffa05ab920 R14:
ffff88006dd123c0 R15: ffff88007b94dc00
Jan 18 02:12:09 mate kernel: [ 117.220091] FS:
00007f37105bb820(0000) GS:ffff88007f500000(0000) knlGS:0000000000000000
Jan 18 02:12:09 mate kernel: [ 117.220091] CS: 0010 DS: 0000 ES:
0000 CR0: 0000000080050033
Jan 18 02:12:09 mate kernel: [ 117.220091] CR2: 000000000378b248 CR3:
000000007a079000 CR4: 00000000000006e0
Jan 18 02:12:09 mate kernel: [ 117.220091] DR0: 0000000000000000 DR1:
0000000000000000 DR2: 0000000000000000
Jan 18 02:12:09 mate kernel: [ 117.220091] DR3: 0000000000000000 DR6:
00000000ffff0ff0 DR7: 0000000000000400
Jan 18 02:12:09 mate kernel: [ 117.220091] Process camera_factory_
(pid: 3154, threadinfo ffff8800794a0000, task ffff880071f6d820)
Jan 18 02:12:09 mate kernel: [ 117.220091] Stack:
Jan 18 02:12:09 mate kernel: [ 117.220091] ffff8800378e7000
ffffffffa05a46b9 ffff88007a2fd040 ffffffff81042cf3
Jan 18 02:12:09 mate kernel: [ 117.220091] 0000000000000001
ffffffff00000001 ffffffff8103dadb 0000000000000001
Jan 18 02:12:09 mate kernel: [ 117.220091] ffff88007ba3e400
ffffffffa03302ff 00000000000135c0 00000000000135c0
Jan 18 02:12:09 mate kernel: [ 117.220091] Call Trace:
Jan 18 02:12:09 mate kernel: [ 117.220091] [<ffffffffa05a46b9>] ?
vidioc_streamoff+0xa6/0xb6 [em28xx]
Jan 18 02:12:09 mate kernel: [ 117.220091] [<ffffffff81042cf3>] ?
get_parent_ip+0x9/0x1b
Jan 18 02:12:09 mate kernel: [ 117.220091] [<ffffffff8103dadb>] ?
need_resched+0x1a/0x23
Jan 18 02:12:09 mate kernel: [ 117.220091] [<ffffffffa03302ff>] ?
__video_do_ioctl+0x12e2/0x33a0 [videodev]
Jan 18 02:12:09 mate kernel: [ 117.220091] [<ffffffff8103a5fe>] ?
__wake_up_common+0x41/0x78
Jan 18 02:12:09 mate kernel: [ 117.220091] [<ffffffff8103da1b>] ?
__wake_up+0x35/0x46
Jan 18 02:12:09 mate kernel: [ 117.220091] [<ffffffff81042cf3>] ?
get_parent_ip+0x9/0x1b
Jan 18 02:12:09 mate kernel: [ 117.220091] [<ffffffff81044d80>] ?
add_preempt_count+0x9e/0xa0
Jan 18 02:12:09 mate kernel: [ 117.220091] [<ffffffff8132935c>] ?
_raw_spin_lock_irqsave+0x40/0x61
Jan 18 02:12:09 mate kernel: [ 117.220091] [<ffffffffa03326f4>] ?
video_ioctl2+0x2ad/0x35d [videodev]
Jan 18 02:12:09 mate kernel: [ 117.220091] [<ffffffff81042cf3>] ?
get_parent_ip+0x9/0x1b
Jan 18 02:12:09 mate kernel: [ 117.220091] [<ffffffffa032e342>] ?
v4l2_ioctl+0x74/0x113 [videodev]
Jan 18 02:12:09 mate kernel: [ 117.220091] [<ffffffff81106f51>] ?
do_vfs_ioctl+0x418/0x465
Jan 18 02:12:09 mate kernel: [ 117.220091] [<ffffffff81106fda>] ?
sys_ioctl+0x3c/0x5e
Jan 18 02:12:09 mate kernel: [ 117.220091] [<ffffffff81009c52>] ?
system_call_fastpath+0x16/0x1b
Jan 18 02:12:09 mate kernel: [ 117.220091] Code: 03 4c 39 e3 0f 18 08
75 d4 31 c0 eb 05 b8 ea ff ff ff 5b 5d 41 5c c3 48 83 ec 08 8b 57 0c
89 f0 89 c1 48 8b 37 21 d1 39 c1 74 04<0f> 0b eb fe 89 c8 f7 d0 21 c2
89 57 0c 21 86 d0 09 00 00 83 3d Jan 18 02:12:09 mate kernel: [
117.220091] RIP [<ffffffffa05a37f4>] res_free+0x14/0x49 [em28xx]
Jan 18 02:12:09 mate kernel: [ 117.220091] RSP<ffff8800794a1c48>
Jan 18 02:12:09 mate kernel: [ 117.264998] ---[ end trace
6d6576ecd99356c8 ]---
I hope this helps.
Regards
Rune
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