imdecode jpeg2000 segfault or deadlock in multithreading

[robinechuca]

Expected behaviour

In the main thread, it works well as written in the example bellow:

import multiprocessing.pool
import cv2
import numpy as np
import tqdm
 
img = np.random.randint(0, 65335, (1024, 1024), dtype=np.uint16)
_, img_data = cv2.imencode(".jp2", img)
n = 100
 
def read(i):
    image = cv2.imdecode(buffer, cv2.IMREAD_ANYDEPTH | cv2.IMREAD_GRAYSCALE)
 
list(tqdm.tqdm(map(read, range(n)), total=n, desc="main thread main process"))
with multiprocessing.pool.Pool() as pool:
   list(tqdm.tqdm(pool.imap_unordered(read, range(n)), total=n, desc="main thread child process"))

Actual behaviour

But in a thread, it is all broken!

import multiprocessing.pool
import cv2
import numpy as np
import tqdm
 
img = np.random.randint(0, 65335, (1024, 1024), dtype=np.uint16)
_, img_data = cv2.imencode(".jp2", img)
n = 100
 
def read(i):
    image = cv2.imdecode(buffer, cv2.IMREAD_ANYDEPTH | cv2.IMREAD_GRAYSCALE)
 
with multiprocessing.pool.ThreadPool() as pool:
   list(tqdm.tqdm(pool.imap_unordered(read, range(n)), total=n, desc="child thread main process"))

When the code does not freeze by itself, an interrupt with ctrl+c leads allways to a segfault. Unlike the threadless example.

Steps to reproduce

• Tested on Debian, Ubuntu and Mint
• Version 4.9.0 of opencv-contrib-python-headless
• Tested on python 3.9, 3.10, 3.11 and 3.12
• architecture x86

[opencv-alalek]

But in a thread

Ensure that there are real threads. Because forked processes don't work: opencv/opencv#5150

[robinechuca]

I've just checked carefully.
Whether with a context fork or spawn, the function executes perfectly.
However, as soon as the thread, not the process, is no longer the principal, there seems to be a conflict with the GIL.

If we start a spawn process in each sub-threads. It works. But it is extremely slow to create a new spawn process each time!
But to create a fork process in each sub-thread doesn't solve anything.

[asmorkalov]

@robinechuca Please publish your cv.getBuildInformation() output. I just tried your reproducer with 4.10.0.84 and it works just fine. BTW, OpenCV supports Jasper and OpenJPEG as back-end for JPEG2K. The first one is buggy and not supported for a long time. We recommend to use the second one, if you build OpenCV from source code.

[robinechuca]

Here's the complete output of cv2.getBuildInformation():

General configuration for OpenCV 4.10.0 =====================================
  Version control:               4.10.0

  Extra modules:
    Location (extra):            /io/opencv_contrib/modules
    Version control (extra):     4.10.0

  Platform:
    Timestamp:                   2024-06-17T17:57:41Z
    Host:                        Linux 5.15.0-1064-azure x86_64
    CMake:                       3.29.5
    CMake generator:             Unix Makefiles
    CMake build tool:            /bin/gmake
    Configuration:               Release

  CPU/HW features:
    Baseline:                    SSE SSE2 SSE3
      requested:                 SSE3
    Dispatched code generation:  SSE4_1 SSE4_2 FP16 AVX AVX2 AVX512_SKX
      requested:                 SSE4_1 SSE4_2 AVX FP16 AVX2 AVX512_SKX
      SSE4_1 (16 files):         + SSSE3 SSE4_1
      SSE4_2 (1 files):          + SSSE3 SSE4_1 POPCNT SSE4_2
      FP16 (0 files):            + SSSE3 SSE4_1 POPCNT SSE4_2 FP16 AVX
      AVX (8 files):             + SSSE3 SSE4_1 POPCNT SSE4_2 AVX
      AVX2 (36 files):           + SSSE3 SSE4_1 POPCNT SSE4_2 FP16 FMA3 AVX AVX2
      AVX512_SKX (5 files):      + SSSE3 SSE4_1 POPCNT SSE4_2 FP16 FMA3 AVX AVX2 AVX_512F AVX512_COMMON AVX512_SKX

  C/C++:
    Built as dynamic libs?:      NO
    C++ standard:                11
    C++ Compiler:                /opt/rh/devtoolset-10/root/usr/bin/c++  (ver 10.2.1)
    C++ flags (Release):         -Wl,-strip-all   -fsigned-char -W -Wall -Wreturn-type -Wnon-virtual-dtor -Waddress -Wsequence-point -Wformat -Wformat-security -Wmissing-declarations -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -Wuninitialized -Wsuggest-override -Wno-delete-non-virtual-dtor -Wno-comment -Wimplicit-fallthrough=3 -Wno-strict-overflow -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -ffunction-sections -fdata-sections  -msse -msse2 -msse3 -fvisibility=hidden -fvisibility-inlines-hidden -O3 -DNDEBUG  -DNDEBUG
    C++ flags (Debug):           -Wl,-strip-all   -fsigned-char -W -Wall -Wreturn-type -Wnon-virtual-dtor -Waddress -Wsequence-point -Wformat -Wformat-security -Wmissing-declarations -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -Wuninitialized -Wsuggest-override -Wno-delete-non-virtual-dtor -Wno-comment -Wimplicit-fallthrough=3 -Wno-strict-overflow -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -ffunction-sections -fdata-sections  -msse -msse2 -msse3 -fvisibility=hidden -fvisibility-inlines-hidden -g  -O0 -DDEBUG -D_DEBUG
    C Compiler:                  /opt/rh/devtoolset-10/root/usr/bin/cc
    C flags (Release):           -Wl,-strip-all   -fsigned-char -W -Wall -Wreturn-type -Waddress -Wsequence-point -Wformat -Wformat-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wshadow -Wuninitialized -Wno-comment -Wimplicit-fallthrough=3 -Wno-strict-overflow -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -ffunction-sections -fdata-sections  -msse -msse2 -msse3 -fvisibility=hidden -O3 -DNDEBUG  -DNDEBUG
    C flags (Debug):             -Wl,-strip-all   -fsigned-char -W -Wall -Wreturn-type -Waddress -Wsequence-point -Wformat -Wformat-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wshadow -Wuninitialized -Wno-comment -Wimplicit-fallthrough=3 -Wno-strict-overflow -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -ffunction-sections -fdata-sections  -msse -msse2 -msse3 -fvisibility=hidden -g  -O0 -DDEBUG -D_DEBUG
    Linker flags (Release):      -Wl,--exclude-libs,libippicv.a -Wl,--exclude-libs,libippiw.a -L/ffmpeg_build/lib  -Wl,--gc-sections -Wl,--as-needed -Wl,--no-undefined  
    Linker flags (Debug):        -Wl,--exclude-libs,libippicv.a -Wl,--exclude-libs,libippiw.a -L/ffmpeg_build/lib  -Wl,--gc-sections -Wl,--as-needed -Wl,--no-undefined  
    ccache:                      YES
    Precompiled headers:         NO
    Extra dependencies:          /lib64/libopenblas.so /usr/local/lib/libpng.so /lib64/libz.so Iconv::Iconv dl m pthread rt
    3rdparty dependencies:       libprotobuf ade ittnotify libjpeg-turbo libwebp libtiff libopenjp2 IlmImf ippiw ippicv

  OpenCV modules:
    To be built:                 aruco bgsegm bioinspired calib3d ccalib core datasets dnn dnn_objdetect dnn_superres dpm face features2d flann fuzzy gapi hfs highgui img_hash imgcodecs imgproc intensity_transform line_descriptor mcc ml objdetect optflow phase_unwrapping photo plot python3 quality rapid reg rgbd saliency shape signal stereo stitching structured_light superres surface_matching text tracking video videoio videostab wechat_qrcode xfeatures2d ximgproc xobjdetect xphoto
    Disabled:                    world
    Disabled by dependency:      -
    Unavailable:                 alphamat cannops cudaarithm cudabgsegm cudacodec cudafeatures2d cudafilters cudaimgproc cudalegacy cudaobjdetect cudaoptflow cudastereo cudawarping cudev cvv freetype hdf java julia matlab ovis python2 sfm ts viz
    Applications:                -
    Documentation:               NO
    Non-free algorithms:         NO

  GUI:                           NONE
    VTK support:                 NO

  Media I/O: 
    ZLib:                        /lib64/libz.so (ver 1.2.7)
    JPEG:                        build-libjpeg-turbo (ver 3.0.3-70)
      SIMD Support Request:      YES
      SIMD Support:              YES
    WEBP:                        build (ver encoder: 0x020f)
    PNG:                         /usr/local/lib/libpng.so (ver 1.6.43)
    TIFF:                        build (ver 42 - 4.6.0)
    JPEG 2000:                   build (ver 2.5.0)
    OpenEXR:                     build (ver 2.3.0)
    HDR:                         YES
    SUNRASTER:                   YES
    PXM:                         YES
    PFM:                         YES

  Video I/O:
    DC1394:                      NO
    FFMPEG:                      YES
      avcodec:                   YES (59.37.100)
      avformat:                  YES (59.27.100)
      avutil:                    YES (57.28.100)
      swscale:                   YES (6.7.100)
      avresample:                NO
    GStreamer:                   NO
    v4l/v4l2:                    YES (linux/videodev2.h)

  Parallel framework:            pthreads

  Trace:                         YES (with Intel ITT)

  Other third-party libraries:
    Intel IPP:                   2021.11.0 [2021.11.0]
           at:                   /io/_skbuild/linux-x86_64-3.9/cmake-build/3rdparty/ippicv/ippicv_lnx/icv
    Intel IPP IW:                sources (2021.11.0)
              at:                /io/_skbuild/linux-x86_64-3.9/cmake-build/3rdparty/ippicv/ippicv_lnx/iw
    VA:                          NO
    Lapack:                      YES (/lib64/libopenblas.so)
    Eigen:                       NO
    Custom HAL:                  NO
    Protobuf:                    build (3.19.1)
    Flatbuffers:                 builtin/3rdparty (23.5.9)

  OpenCL:                        YES (no extra features)
    Include path:                /io/opencv/3rdparty/include/opencl/1.2
    Link libraries:              Dynamic load

  Python 3:
    Interpreter:                 /opt/python/cp39-cp39/bin/python3.9 (ver 3.9.19)
    Libraries:                   libpython3.9m.a (ver 3.9.19)
    Limited API:                 YES (ver 0x03060000)
    numpy:                       /home/ci/.local/lib/python3.9/site-packages/numpy/_core/include (ver 2.0.0)
    install path:                python/cv2/python-3

  Python (for build):            /opt/python/cp39-cp39/bin/python3.9

  Java:                          
    ant:                         NO
    Java:                        NO
    JNI:                         NO
    Java wrappers:               NO
    Java tests:                  NO

  Install to:                    /io/_skbuild/linux-x86_64-3.9/cmake-install
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