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Message-ID: <4D36B81B.9000602@gmail.com> Date: Wed, 19 Jan 2011 11:08:27 +0100 From: Patrik Jakobsson <patrik.r.jakobsson@...il.com> To: Hans Verkuil <hverkuil@...all.nl> CC: Rune Saetre <rune.saetre@...omar.com>, linux-kernel@...r.kernel.org, linux-media@...r.kernel.org Subject: Re: PROBLEM: kernel BUG at drivers/media/video/em28xx/em28xx-video.c:891 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@linuxtv.org/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 >>> >>> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-media" in >> the body of a message to majordomo@...r.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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