[FFmpeg-cvslog] pngdec: frame multithreading support
Reimar Döffinger
Reimar.Doeffinger at gmx.de
Sat Aug 24 21:46:14 CEST 2013
On Fri, Aug 23, 2013 at 08:33:35PM +0200, Michael Niedermayer wrote:
> On Fri, Aug 23, 2013 at 06:19:21PM +0000, Paul B Mahol wrote:
> > 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.
>
> I think that after ff_thread_finish_setup() a thread has to produce
> some frame with full progress.
I guess we might not have support for it for PNG, but I think the idea/right thing
to do is for a thread to return an error-concealed frame when it "fails".
I guess it would also mean that it might make sense to only do
ff_thread_finish_setup if there is at least some data that error
concealment can be run on (though I admit that might be messy)...
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