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?
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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