[FFmpeg-cvslog] pngdec: frame multithreading support
Paul B Mahol
onemda at gmail.com
Fri Aug 23 20:19:21 CEST 2013
On 8/23/13, Michael Niedermayer <michaelni at gmx.at> wrote:
> On Thu, Aug 22, 2013 at 04:45:58PM +0200, Paul B Mahol wrote:
>> ffmpeg | branch: master | Paul B Mahol <onemda at gmail.com> | Mon Aug 12
>> 10:56:20 2013 +0000| [6e643239d9956ce32888d87451706ee7c8757afa] |
>> committer: Paul B Mahol
>>
>> pngdec: frame multithreading support
>>
>> Signed-off-by: Paul B Mahol <onemda at gmail.com>
>>
>> > http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=6e643239d9956ce32888d87451706ee7c8757afa
>> ---
>>
>> libavcodec/pngdec.c | 69
>> +++++++++++++++++++++++++++++++++++++--------------
>> 1 file changed, 51 insertions(+), 18 deletions(-)
>
> It seems this still deadlocks and crashes occasionally but not
> always (same file as the last one)
>
> Deadlock: (duplicate backtraces ommited)
>
> Thread 27 (Thread 0x7fffe017f700 (LWP 10742)):
> #0 pthread_cond_wait@@GLIBC_2.3.2 () at
> ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:162
> #1 0x00000000008e16a7 in frame_worker_thread (arg=0x1743520) at
> libavcodec/pthread.c:330
> #2 0x00007ffff0467e9a in start_thread (arg=0x7fffe017f700) at
> pthread_create.c:308
> #3 0x00007ffff0194ccd in clone () at
> ../sysdeps/unix/sysv/linux/x86_64/clone.S:112
> #4 0x0000000000000000 in ?? ()
>
>
> Thread 21 (Thread 0x7fffe3185700 (LWP 10736)):
> #0 pthread_cond_wait@@GLIBC_2.3.2 () at
> ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:162
> #1 0x00000000008e26d7 in ff_thread_await_progress (f=0x173add0,
> n=2147483647, field=0) at libavcodec/pthread.c:692
> #2 0x00000000008d3d42 in decode_frame (avctx=0x173a920, data=0x1741dd0,
> got_frame=0x1742040, avpkt=0x1741d60) at libavcodec/pngdec.c:843
> #3 0x00000000008e176f in frame_worker_thread (arg=0x1741c60) at
> libavcodec/pthread.c:339
> #4 0x00007ffff0467e9a in start_thread (arg=0x7fffe3185700) at
> pthread_create.c:308
> #5 0x00007ffff0194ccd in clone () at
> ../sysdeps/unix/sysv/linux/x86_64/clone.S:112
> #6 0x0000000000000000 in ?? ()
>
> Thread 1 (Thread 0x7ffff7faa780 (LWP 10714)):
> #0 pthread_cond_wait@@GLIBC_2.3.2 () at
> ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:162
> #1 0x00000000008e23d7 in ff_thread_decode_frame (avctx=0x174fec0,
> picture=0x174b1e0, got_picture_ptr=0x7fffffffdca8, avpkt=0x7fffffffd9d0) at
> libavcodec/pthread.c:631
> #2 0x0000000000982228 in avcodec_decode_video2 (avctx=0x174fec0,
> picture=0x174b1e0, got_picture_ptr=0x7fffffffdca8, avpkt=0x7fffffffdbf0) at
> libavcodec/utils.c:1979
> #3 0x0000000000424306 in decode_video (ist=0x1752780, pkt=0x7fffffffdbf0,
> got_output=0x7fffffffdca8) at ffmpeg.c:1668
> #4 0x0000000000425193 in output_packet (ist=0x1752780, pkt=0x7fffffffdd70)
> at ffmpeg.c:1866
> #5 0x000000000042ad63 in process_input (file_index=0) at ffmpeg.c:3085
> #6 0x000000000042b0e2 in transcode_step () at ffmpeg.c:3181
> #7 0x000000000042b1ef in transcode () at ffmpeg.c:3233
> #8 0x000000000042b71a in main (argc=11, argv=0x7fffffffe398) at
> ffmpeg.c:3411
>
> ------------
> segfault (again same file, doesnt happe under valgrind)
>
> Program received signal SIGSEGV, Segmentation fault.
> [Switching to Thread 0x7fffe2d26700 (LWP 19664)]
> malloc_consolidate (av=0x7fffc0000020) at malloc.c:4251
> 4251 malloc.c: No such file or directory.
> (gdb) bt
> #0 malloc_consolidate (av=0x7fffc0000020) at malloc.c:4251
> #1 0x00007fffef4c1446 in malloc_consolidate (av=0x7fffc0000020) at
> malloc.c:4226
> #2 _int_malloc (av=0x7fffc0000020, bytes=7232) at malloc.c:3543
> #3 0x00007fffef4c2811 in _int_memalign (av=0x7fffc0000020, alignment=32,
> bytes=<optimized out>) at malloc.c:4503
> #4 0x00007fffef4c4aa6 in __GI___libc_memalign (alignment=32, bytes=7152) at
> malloc.c:3104
> #5 0x00007fffef4c5d19 in __posix_memalign (memptr=0x7fffe2d25cb8,
> alignment=<optimized out>, size=<optimized out>) at malloc.c:5049
> #6 0x0000000000bd2bda in av_malloc (size=7152) at libavutil/mem.c:93
> #7 av_mallocz (size=7152) at libavutil/mem.c:223
> #8 0x00007fffefe445b7 in inflateInit2_ () from
> /lib/x86_64-linux-gnu/libz.so.1
> #9 0x00000000008fd864 in decode_frame (avctx=0x16d2c40, data=0x16db150,
> got_frame=0x16db3c0, avpkt=0x16db0e0) at libavcodec/pngdec.c:539
> #10 0x000000000090a755 in frame_worker_thread (arg=0x16dafe0) at
> libavcodec/pthread.c:339
> #11 0x00007fffef807e9a in start_thread (arg=0x7fffe2d26700) at
> pthread_create.c:308
> #12 0x00007fffef534ccd in clone () at
> ../sysdeps/unix/sysv/linux/x86_64/clone.S:112
> #13 0x0000000000000000 in ?? ()
>
> asan shows these:
>
> =================================================================
> ==29015==ERROR: AddressSanitizer: heap-use-after-free on address
> 0x60700001f74c at pc 0x13757b0 bp 0x7f8a041959a0 sp 0x7f8a04195998
> WRITE of size 4 at 0x60700001f74c thread T20
> #0 0x13757af in atomic_int_add_and_fetch_gcc
> ffmpeg/libavutil/atomic_gcc.h:45
> #1 0x1375887 in av_buffer_unref ffmpeg/libavutil/buffer.c:114
> #2 0x13819d8 in av_frame_unref ffmpeg/libavutil/frame.c:347
> #3 0xdbca46 in decode_frame ffmpeg/libavcodec/pngdec.c:519
> #4 0xde0d25 in frame_worker_thread ffmpeg/libavcodec/pthread.c:339
> #5 0x466e73 in _ZN6__asan10AsanThread11ThreadStartEm ??:0
> #6 0x7f8a175c0e99 in start_thread
> /build/buildd/eglibc-2.15/nptl/pthread_create.c:308
> #7 0x7f8a16ed3ccc in ??
> /build/buildd/eglibc-2.15/misc/../sysdeps/unix/sysv/linux/x86_64/clone.S:112
> 0x60700001f74c is located 12 bytes inside of 40-byte region
> [0x60700001f740,0x60700001f768)
> freed by thread T19 here:
> #0 0x4607f4 in free ??:0
> #1 0x138d9f1 in av_freep ffmpeg/libavutil/mem.c:217
> #2 0x13758f1 in av_buffer_unref ffmpeg/libavutil/buffer.c:116
> #3 0x13819d8 in av_frame_unref ffmpeg/libavutil/frame.c:347
> #4 0xdc018d in decode_frame ffmpeg/libavcodec/pngdec.c:872
> #5 0xde0d25 in frame_worker_thread ffmpeg/libavcodec/pthread.c:339
> #6 0x466e73 in _ZN6__asan10AsanThread11ThreadStartEm ??:0
> previously allocated by thread T19 here:
> #0 0x460b6c in posix_memalign ??:0
> #1 0x138d6e0 in av_malloc ffmpeg/libavutil/mem.c:93
> #2 0x138da2e in av_mallocz ffmpeg/libavutil/mem.c:223
> #3 0x137523a in av_buffer_create ffmpeg/libavutil/buffer.c:34
> #4 0x1375584 in av_buffer_alloc ffmpeg/libavutil/buffer.c:74
> #5 0x13755dd in av_buffer_allocz ffmpeg/libavutil/buffer.c:83
> #6 0x1376817 in pool_alloc_buffer ffmpeg/libavutil/buffer.c:305
> #7 0xf07ca8 in video_get_buffer ffmpeg/libavcodec/utils.c:574
> #8 0xf094a4 in get_buffer_internal ffmpeg/libavcodec/utils.c:864
> #9 0xf08e1e in ff_get_buffer ffmpeg/libavcodec/utils.c:876
> #10 0xddeb6f in thread_get_buffer_internal
> ffmpeg/libavcodec/pthread.c:962
> #11 0xdde6ae in ff_thread_get_buffer ffmpeg/libavcodec/pthread.c:1017
> #12 0xdbe5be in decode_frame ffmpeg/libavcodec/pngdec.c:646
> #13 0xde0d25 in frame_worker_thread ffmpeg/libavcodec/pthread.c:339
> #14 0x466e73 in _ZN6__asan10AsanThread11ThreadStartEm ??:0
> Thread T20 created by T0 here:
> #0 0x45c9d8 in __interceptor_pthread_create ??:0
> #1 0xde0075 in frame_thread_init ffmpeg/libavcodec/pthread.c:872
> #2 0xf0b73c in avcodec_open2 ffmpeg/libavcodec/utils.c:1222
> #3 0x4a6354 in init_input_stream ffmpeg/ffmpeg.c:1983
> #4 0x49074a in transcode_init ffmpeg/ffmpeg.c:2486
> #5 0x48bff2 in transcode ffmpeg/ffmpeg.c:3204
> #6 0x48b462 in main ffmpeg/ffmpeg.c:3411
> #7 0x7f8a16e0176c in __libc_start_main
> /build/buildd/eglibc-2.15/csu/libc-start.c:226
> Thread T19 created by T0 here:
> #0 0x45c9d8 in __interceptor_pthread_create ??:0
> #1 0xde0075 in frame_thread_init ffmpeg/libavcodec/pthread.c:872
> #2 0xf0b73c in avcodec_open2 ffmpeg/libavcodec/utils.c:1222
> #3 0x4a6354 in init_input_stream ffmpeg/ffmpeg.c:1983
> #4 0x49074a in transcode_init ffmpeg/ffmpeg.c:2486
> #5 0x48bff2 in transcode ffmpeg/ffmpeg.c:3204
> #6 0x48b462 in main ffmpeg/ffmpeg.c:3411
> #7 0x7f8a16e0176c in __libc_start_main
> /build/buildd/eglibc-2.15/csu/libc-start.c:226
>
> ---------
> a different one:
> ==29194==ERROR: AddressSanitizer: heap-use-after-free on address
> 0x605000002780 at pc 0x1375763 bp 0x7fffeb33d210 sp 0x7fffeb33d208
> READ of size 24 at 0x605000002780 thread T0
> #0 0x1375762 in av_buffer_ref ffmpeg/libavutil/buffer.c:98
> #1 0xf167da in ff_thread_ref_frame ffmpeg/libavcodec/utils.c:3151
> #2 0xddc447 in submit_packet ffmpeg/libavcodec/pthread.c:519
> #3 0xddb48b in ff_thread_decode_frame ffmpeg/libavcodec/pthread.c:602
> #4 0xf10358 in avcodec_decode_video2 ffmpeg/libavcodec/utils.c:1979
> #5 0x499bc5 in decode_video ffmpeg/ffmpeg.c:1668
> #6 0x49542c in output_packet ffmpeg/ffmpeg.c:1866
> #7 0x4a198b in process_input ffmpeg/ffmpeg.c:3085
> #8 0x49332f in transcode_step ffmpeg/ffmpeg.c:3181
> #9 0x48c083 in transcode ffmpeg/ffmpeg.c:3233
> #10 0x48b462 in main ffmpeg/ffmpeg.c:3411
> #11 0x7f8cba42476c in __libc_start_main
> /build/buildd/eglibc-2.15/csu/libc-start.c:226
> #12 0x46e93c in _start ??:0
> 0x605000002780 is located 0 bytes inside of 24-byte region
> [0x605000002780,0x605000002798)
> freed by thread T19 here:
> #0 0x4607f4 in free ??:0
> #1 0x138d9f1 in av_freep ffmpeg/libavutil/mem.c:217
> #2 0x1375867 in av_buffer_unref ffmpeg/libavutil/buffer.c:112
> #3 0xddeee1 in ff_thread_release_buffer
> ffmpeg/libavcodec/pthread.c:1044
> #4 0xdc018d in decode_frame ffmpeg/libavcodec/pngdec.c:872
> #5 0xde0d25 in frame_worker_thread ffmpeg/libavcodec/pthread.c:339
> #6 0x466e73 in _ZN6__asan10AsanThread11ThreadStartEm ??:0
> previously allocated by thread T19 here:
> #0 0x460b6c in posix_memalign ??:0
> #1 0x138d6e0 in av_malloc ffmpeg/libavutil/mem.c:93
> #2 0x138da2e in av_mallocz ffmpeg/libavutil/mem.c:223
> #3 0x13753ae in av_buffer_create ffmpeg/libavutil/buffer.c:47
> #4 0x1375584 in av_buffer_alloc ffmpeg/libavutil/buffer.c:74
> #5 0xdde8cf in thread_get_buffer_internal
> ffmpeg/libavcodec/pthread.c:944
> #6 0xdde6ae in ff_thread_get_buffer ffmpeg/libavcodec/pthread.c:1017
> #7 0xdbe5be in decode_frame ffmpeg/libavcodec/pngdec.c:646
> #8 0xde0d25 in frame_worker_thread ffmpeg/libavcodec/pthread.c:339
> #9 0x466e73 in _ZN6__asan10AsanThread11ThreadStartEm ??:0
> Thread T19 created by T0 here:
> #0 0x45c9d8 in __interceptor_pthread_create ??:0
> #1 0xde0075 in frame_thread_init ffmpeg/libavcodec/pthread.c:872
> #2 0xf0b73c in avcodec_open2 ffmpeg/libavcodec/utils.c:1222
> #3 0x4a6354 in init_input_stream ffmpeg/ffmpeg.c:1983
> #4 0x49074a in transcode_init ffmpeg/ffmpeg.c:2486
> #5 0x48bff2 in transcode ffmpeg/ffmpeg.c:3204
> #6 0x48b462 in main ffmpeg/ffmpeg.c:3411
> #7 0x7f8cba42476c in __libc_start_main
> /build/buildd/eglibc-2.15/csu/libc-start.c:226
If relasing buffer on failure is not correct solution because other threads
may still use it, I wonder what should be done on failure instead?
Perhaps memset whole frame to 0 and report full progress?
I think its obvious to anyone why deadlock happens. One thread fails
decoding and another one is waiting for first one to finish decoding as failed
one never returns any progress it wait forever.
>
> [...]
> --
> Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
>
> During times of universal deceit, telling the truth becomes a
> revolutionary act. -- George Orwell
>
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