videobuf2_common: driver bug: stop_streaming operation is leaving buf 0b70dd47 in active state

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
30/100
Issue type
Bug
Clarity
Needs clarification
Activity status
Stale
Tech stack
c, linux
Domain
embedded-iot, operating-systems

Research direction

Start at drivers/media/common/videobuf2/videobuf2-core.c around __vb2_queue_cancel and trace the vb2_core_streamoff path shown in the report. Compare it with bcm2835_codec_stop_streaming and the Raspberry Pi camera pipeline, then reproduce stream shutdown on the reported hardware. Done means stopping the stream no longer leaves buffers active or emits the videobuf2 warning.

Written by the indexing model from the issue text.

Description

I hit this "driver bug" after stopping an IP camera stream that was left open overnight. The software uses OpenCV to read camera frames using a gstreamer pipeline like this: "rtspsrc protocols=tcp tcp-timeout=2000000 retry=2 do-retransmission=false location=rtsp://192.168.42.10:554/user=admin&password=&channel=1&stream=0.sdp ! rtpjitter
buffer ! rtph264depay ! queue ! h264parse ! v4l2h264dec ! queue ! appsink sync=1"

Model: Raspberry Pi 3B

$ cat /etc/rpi-issue
Raspberry Pi reference 2020-05-27
Generated using pi-gen, https://github.com/RPi-Distro/pi-gen, 825107f04027269db77426046f5085475b1ea22f, stage2

$ vcgencmd version
Jul 17 2020 11:04:27
Copyright (c) 2012 Broadcom
version 21a15cb094f41c7506ad65d2cb9b29c550693057 (clean) (release) (start)

$ uname -a
Linux br0001 5.4.51-v7+ #1327 SMP Thu Jul 23 10:58:46 BST 2020 armv7l GNU/Linux

[Thu Aug 13 10:12:33 2020] bcm2835-codec bcm2835-codec: bcm2835_codec_stop_streaming: Timeout waiting for buffers to be returned - 11 outstanding
[Thu Aug 13 10:12:33 2020] ------------[ cut here ]------------
[Thu Aug 13 10:12:33 2020] WARNING: CPU: 0 PID: 13924 at drivers/media/common/videobuf2/videobuf2-core.c:1882 __vb2_queue_cancel+0x210/0x288 [videobuf2_common]
[Thu Aug 13 10:12:33 2020] Modules linked in: cmac bnep hci_uart btbcm bluetooth ecdh_generic ecc 8021q garp stp llc brcmfmac brcmutil sha256_generic libsha256 cfg80211 raspberrypi_hwmon rfkill i2c_bcm2835 bcm2835_codec(C) bcm2835_isp(C) bcm2835_v4l2(C) v4l2_mem2mem snd_bcm2835(C) bcm2835_mmal_vchiq(C) videobuf2_dma_contig videobuf2_vmalloc videobuf2_memops snd_pcm videobuf2_v4l2 videobuf2_common snd_timer videodev snd mc vc_sm_cma(C) uio_pdrv_genirq uio fixed i2c_dev ip_tables x_tables ipv6 nf_defrag_ipv6
[Thu Aug 13 10:12:33 2020] CPU: 0 PID: 13924 Comm: python Tainted: G WC 5.4.51-v7+ #1327
[Thu Aug 13 10:12:33 2020] Hardware name: BCM2835
[Thu Aug 13 10:12:33 2020] Backtrace:
[Thu Aug 13 10:12:33 2020] [<8010d458>] (dump_backtrace) from [<8010d750>] (show_stack+0x20/0x24)
[Thu Aug 13 10:12:33 2020] r6:8bcf6000 r5:00000000 r4:80d93ff4 r3:82a41469
[Thu Aug 13 10:12:33 2020] [<8010d730>] (show_stack) from [<808b2324>] (dump_stack+0xe0/0x124)
[Thu Aug 13 10:12:33 2020] [<808b2244>] (dump_stack) from [<8011fd24>] (__warn+0xec/0x104)
[Thu Aug 13 10:12:33 2020] r8:0000075a r7:00000009 r6:7f0ca7c4 r5:00000000 r4:00000000 r3:82a41469
[Thu Aug 13 10:12:33 2020] [<8011fc38>] (__warn) from [<8011fdf4>] (warn_slowpath_fmt+0xb8/0xc0)
[Thu Aug 13 10:12:33 2020] r9:7f0ca7c4 r8:0000075a r7:7f0c519c r6:00000009 r5:00000000 r4:80d04f48
[Thu Aug 13 10:12:33 2020] [<8011fd40>] (warn_slowpath_fmt) from [<7f0c519c>] (__vb2_queue_cancel+0x210/0x288 [videobuf2_common])
[Thu Aug 13 10:12:33 2020] r9:afa8b40c r8:40045613 r7:7f165ee0 r6:afa8b40c r5:00000009 r4:afa8b40c
[Thu Aug 13 10:12:33 2020] [<7f0c4f8c>] (__vb2_queue_cancel [videobuf2_common]) from [<7f0c6b00>] (vb2_core_streamoff+0x44/0xb4 [videobuf2_common])
[Thu Aug 13 10:12:33 2020] r10:b1bd27c8 r9:00000020 r8:40045613 r7:7f165ee0 r6:afa8b40c r5:00000009
[Thu Aug 13 10:12:33 2020] r4:afa8b40c r3:00000009
[Thu Aug 13 10:12:33 2020] [<7f0c6abc>] (vb2_core_streamoff [videobuf2_common]) from [<7f0e6084>] (vb2_streamoff+0x40/0x60 [videobuf2_v4l2])
[Thu Aug 13 10:12:33 2020] r4:afa8b400 r3:00000000
[Thu Aug 13 10:12:33 2020] [<7f0e6044>] (vb2_streamoff [videobuf2_v4l2]) from [<7f1d8c08>] (v4l2_m2m_streamoff+0x3c/0xf4 [v4l2_mem2mem])
[Thu Aug 13 10:12:33 2020] [<7f1d8bcc>] (v4l2_m2m_streamoff [v4l2_mem2mem]) from [<7f1d8ce0>] (v4l2_m2m_ioctl_streamoff+0x20/0x24 [v4l2_mem2mem])
[Thu Aug 13 10:12:33 2020] r10:b1bd27c8 r9:00000020 r8:40045613 r7:7f165ee0 r6:80d04f48 r5:00000000
[Thu Aug 13 10:12:33 2020] r4:b1bd24a0 r3:97229000
[Thu Aug 13 10:12:33 2020] [<7f1d8cc0>] (v4l2_m2m_ioctl_streamoff [v4l2_mem2mem]) from [<7f165f08>] (v4l_streamoff+0x28/0x2c [videodev])
[Thu Aug 13 10:12:33 2020] [<7f165ee0>] (v4l_streamoff [videodev]) from [<7f16acb4>] (__video_do_ioctl+0x240/0x470 [videodev])
[Thu Aug 13 10:12:33 2020] [<7f16aa74>] (__video_do_ioctl [videodev]) from [<7f16cd54>] (video_usercopy+0x220/0x60c [videodev])
[Thu Aug 13 10:12:33 2020] r10:7f16aa74 r9:40045613 r8:00000000 r7:8bcf7e04 r6:00000004 r5:00000000
[Thu Aug 13 10:12:33 2020] r4:80d04f48
[Thu Aug 13 10:12:33 2020] [<7f16cb34>] (video_usercopy [videodev]) from [<7f16d160>] (video_ioctl2+0x20/0x24 [videodev])
[Thu Aug 13 10:12:33 2020] r10:00000036 r9:8bcf6000 r8:00000026 r7:8e89a540 r6:b1371690 r5:021f1200
[Thu Aug 13 10:12:33 2020] r4:80d04f48
[Thu Aug 13 10:12:33 2020] [<7f16d140>] (video_ioctl2 [videodev]) from [<7f164144>] (v4l2_ioctl+0x4c/0x60 [videodev])
[Thu Aug 13 10:12:33 2020] [<7f1640f8>] (v4l2_ioctl [videodev]) from [<802f8540>] (do_vfs_ioctl+0xbc/0x804)
[Thu Aug 13 10:12:33 2020] [<802f8484>] (do_vfs_ioctl) from [<802f8ccc>] (ksys_ioctl+0x44/0x6c)
[Thu Aug 13 10:12:33 2020] r10:00000036 r9:8bcf6000 r8:00000026 r7:40045613 r6:8e89a540 r5:021f1200
[Thu Aug 13 10:12:33 2020] r4:8e89a541
[Thu Aug 13 10:12:33 2020] [<802f8c88>] (ksys_ioctl) from [<802f8d0c>] (sys_ioctl+0x18/0x1c)
[Thu Aug 13 10:12:33 2020] r8:801011c4 r7:00000036 r6:4ca637d0 r5:4ca63000 r4:6a308648 r3:76d72510
[Thu Aug 13 10:12:33 2020] [<802f8cf4>] (sys_ioctl) from [<80101000>] (ret_fast_syscall+0x0/0x28)
[Thu Aug 13 10:12:33 2020] Exception stack(0x8bcf7fa8 to 0x8bcf7ff0)
[Thu Aug 13 10:12:33 2020] 7fa0: 6a308648 4ca63000 00000026 40045613 021f1200 76d72510
[Thu Aug 13 10:12:33 2020] 7fc0: 6a308648 4ca63000 4ca637d0 00000036 6a307300 6a4785f0 706e492c 74c73ce8
[Thu Aug 13 10:12:33 2020] 7fe0: 708cfc60 7eb630b4 4ca2b954 76d7251c
[Thu Aug 13 10:12:33 2020] ---[ end trace abd9ddf252533015 ]---
[Thu Aug 13 10:12:33 2020] videobuf2_common: driver bug: stop_streaming operation is leaving buf 0b70dd47 in active state
[Thu Aug 13 10:12:33 2020] videobuf2_common: driver bug: stop_streaming operation is leaving buf b0d5ce36 in active state
[Thu Aug 13 10:12:33 2020] videobuf2_common: driver bug: stop_streaming operation is leaving buf da61dea1 in active state
[Thu Aug 13 10:12:33 2020] videobuf2_common: driver bug: stop_streaming operation is leaving buf d4e41263 in active state
[Thu Aug 13 10:12:33 2020] videobuf2_common: driver bug: stop_streaming operation is leaving buf db4367ac in active state
[Thu Aug 13 10:12:33 2020] videobuf2_common: driver bug: stop_streaming operation is leaving buf 08347a89 in active state

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