core(parallel): plugins support by alalek · Pull Request #19470 · opencv/opencv

alalek · 2021-02-06T16:28:44Z

relates #19365

Usage examples are on GitHub PR page.

TBB plugin build example:

cd plugin_tbb
cmake <opencv>/modules/core/misc/plugins/parallel_tbb
cmake --build . --config Release

OpenMP plugin build example:

cd plugin_openmp
cmake <opencv>/modules/core/misc/plugins/parallel_openmp
cmake --build . --config Release

oneTBB plugin build example (reuse TBB plugin code under different binary name):

cd plugin_onetbb
cmake <opencv>/modules/core/misc/plugins/parallel_tbb -DOPENCV_PLUGIN_OUTPUT_NAME=opencv_core_parallel_onetbb
cmake --build . --config Release

Extra steps for Windows:

cmake -G "Visual Studio 16 2019" -A x64 -DOpenCV_DIR:PATH=...

Install target (no .pdb):

cmake "-DCMAKE_INSTALL_PREFIX:PATH=<opencv_build>/bin/Release" ...`
cmake --build . --config Release --target INSTALL

Hardening option:

cmake -DENABLE_BUILD_HARDENING=ON ...`

Control environment variables:

OPENCV_PARALLEL_PRIORITY_TBB=0 - disable
OPENCV_PARALLEL_PRIORITY_LIST=TBB - preferred backends names
OPENCV_PARALLEL_BACKEND=TBB - forced backend name

Tasks:

force_builders=ARMv7,Custom
build_image:Custom=centos:7
buildworker:Custom=linux-1,linux-4,linux-6

mshabunin · 2021-02-12T15:02:40Z

I have a problem with OpenMP backend built as a plugin (Ubuntu 18):

$ ./bin/opencv_test_core --gtest_filter=*parallel*
<...>
CTEST_FULL_OUTPUT
OpenCV version: 4.5.1-dev
OpenCV VCS version: 4.5.1-143-geb10e518cc-dirty
Build type: Release
Compiler: /usr/bin/c++  (ver 7.5.0)
[DEBUG:0] global /opencv/modules/core/src/parallel/parallel.cpp (103) createDefaultParallelForAPI core(parallel): Initializing parallel backend...
[DEBUG:0] global /opencv/modules/core/src/parallel/registry_parallel.impl.hpp (63) ParallelBackendRegistry core(parallel): Builtin backends(3): ONETBB(1000); TBB(990); OPENMP(980)
[DEBUG:0] global /opencv/modules/core/src/parallel/registry_parallel.impl.hpp (88) ParallelBackendRegistry core(parallel): Available backends(3): ONETBB(1000); TBB(990); OPENMP(980)
[ INFO:0] global /opencv/modules/core/src/parallel/registry_parallel.impl.hpp (90) ParallelBackendRegistry core(parallel): Enabled backends(3, sorted by priority): ONETBB(1000); TBB(990); OPENMP(980)
[ INFO:0] global /opencv/modules/core/src/parallel/parallel.cpp (50) createParallelForAPI core(parallel): requested backend name: OPENMP
[DEBUG:0] global /opencv/modules/core/src/parallel/parallel.cpp (65) createParallelForAPI core(parallel): trying backend: OPENMP (priority=980)
[DEBUG:0] global /opencv/modules/core/src/parallel/plugin_parallel_wrapper.impl.hpp (219) getPluginCandidates core(parallel): OPENMP plugin's glob is 'libopencv_core_parallel_openmp*.so', 1 location(s)
[DEBUG:0] global /opencv/modules/core/src/parallel/plugin_parallel_wrapper.impl.hpp (226) getPluginCandidates     - /build/lib: 1
[DEBUG:0] global /opencv/modules/core/src/parallel/plugin_parallel_wrapper.impl.hpp (230) getPluginCandidates Found 1 plugin(s) for OPENMP
[ INFO:0] global /opencv/modules/core/src/utils/plugin_loader.impl.hpp (43) libraryLoad load /build/lib/libopencv_core_parallel_openmp.so => OK
[DEBUG:0] global /opencv/modules/core/src/parallel/plugin_parallel_wrapper.impl.hpp (31) initPluginAPI Found entry: 'opencv_core_parallel_plugin_init_v0'
[DEBUG:0] global /opencv/modules/core/src/parallel/plugin_parallel_wrapper.impl.hpp (80) checkCompatibility core(parallel): initialized 'OpenMP (201511) OpenCV parallel plugin': built with OpenCV 4.5 (ABI/API = 0/0), current OpenCV version is '4.5.1-dev' (ABI/API = 0/0)
[ INFO:0] global /opencv/modules/core/src/parallel/plugin_parallel_wrapper.impl.hpp (48) initPluginAPI core(parallel): plugin is ready to use 'OpenMP (201511) OpenCV parallel plugin'
[ INFO:0] global /opencv/modules/core/src/parallel/parallel.cpp (73) createParallelForAPI core(parallel): using backend: OPENMP (priority=980)
Parallel framework: openmp (nthreads=8)
CPU features: SSE SSE2 SSE3 *SSE4.1 *SSE4.2 *FP16 *AVX *AVX2 *AVX512-SKX?
Intel(R) IPP version: ippIP AVX2 (l9) 2020.0.0 Gold (-) Oct 19 2019
Intel(R) IPP features code: 0x8000
OpenCL Platforms:
<...>
TEST: Skip tests with tags: 'mem_6gb', 'verylong'
Note: Google Test filter = *parallel*
[==========] Running 1 test from 1 test case.
[----------] Global test environment set-up.
[----------] 1 test from Core_Rand
[ RUN      ] Core_Rand.parallel_for_stable_results
[       OK ] Core_Rand.parallel_for_stable_results (3 ms)
[----------] 1 test from Core_Rand (3 ms total)

[----------] Global test environment tear-down
[==========] 1 test from 1 test case ran. (3 ms total)
[  PASSED  ] 1 test.
[ INFO:0] global /opencv/modules/core/src/utils/plugin_loader.impl.hpp (50) libraryRelease unload /build/lib/libopencv_core_parallel_openmp.so
Segmentation fault

With gdb:

[==========] Running 1 test from 1 test case.
[----------] Global test environment set-up.
[----------] 1 test from Core_Rand
[ RUN      ] Core_Rand.parallel_for_stable_results
[New Thread 0x7fffdbc45700 (LWP 27795)]
[New Thread 0x7fffdb444700 (LWP 27796)]
[New Thread 0x7fffdac43700 (LWP 27797)]
[New Thread 0x7fffda442700 (LWP 27798)]
[New Thread 0x7fffd9c41700 (LWP 27799)]
[New Thread 0x7fffd9440700 (LWP 27800)]
[New Thread 0x7fffd8c3f700 (LWP 27801)]
[       OK ] Core_Rand.parallel_for_stable_results (1 ms)
[----------] 1 test from Core_Rand (1 ms total)

[----------] Global test environment tear-down
[==========] 1 test from 1 test case ran. (3 ms total)
[  PASSED  ] 1 test.
[ INFO:0] global /opencv/modules/core/src/utils/plugin_loader.impl.hpp (50) libraryRelease unload /build/lib/libopencv_core_parallel_openmp.so

Thread 9 "opencv_test_cor" received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7fffd8c3f700 (LWP 27801)]
0x00007fffdbc5ef22 in ?? () from /usr/lib/x86_64-linux-gnu/libgomp.so.1
(gdb) bt
#0  0x00007fffdbc5ef22 in  () at /usr/lib/x86_64-linux-gnu/libgomp.so.1
#1  0x00007fffdbc5c948 in  () at /usr/lib/x86_64-linux-gnu/libgomp.so.1
#2  0x00007ffff79a66db in start_thread (arg=0x7fffd8c3f700) at pthread_create.c:463
#3  0x00007ffff3c0488f in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95

mshabunin · 2021-02-12T14:13:25Z

modules/core/cmake/parallel/plugin.cmake

@@ -0,0 +1,60 @@
+function(ocv_create_builtin_core_parallel_plugin name target)


This file and plugin_standalone.cmake are similar to videoio/cmake/plugin*.cmake. Can they be unified somehow? Maybe moved to the root cmake/ directory?

modules/core/src/parallel/registry_parallel.impl.hpp

alalek

@mshabunin Thanks!
Added task to find workaround for cases with unloading crashes

alalek · 2021-02-12T21:03:18Z

modules/core/cmake/parallel/detect_openmp.cmake

+  message(STATUS "OpenMP detection requires CMake 3.9+")  # OpenMP::OpenMP_CXX target
+endif()
+
+find_package(OpenMP)


libraryRelease unload /build/lib/libopencv_core_parallel_openmp.so
Segmentation fault

LD_DEBUG=libs dump is:

[ PASSED ] 1 test. [ INFO:0] global /home/alalek/projects/opencv/dev/modules/core/src/utils/plugin_loader.impl.hpp (50) libraryRelease unload /home/alalek/projects/opencv/build/opencv/lib/libopencv_core_parallel_openmp.so 232271: 232271: calling fini: /home/alalek/projects/opencv/build/opencv/lib/libopencv_core_parallel_openmp.so [0] 232271: 232271: 232271: calling fini: /lib64/libgomp.so.1 [0] 232271: Segmentation fault (core dumped)

libgomp.so.1 is de-initialized (finit call), but its worker threads are still alive (gdb shows that).

So,

this is a bug of libgomp.so.1 (no idea why worker threads are not terminated during unload stage)

we should not force OpenMP thread pool termination from OpenCV side, because application can use OpenMP directly

some workaround is required (probably don't unload parallel plugins)

The similar issue can be observed with TBB

Issue is sporadic with TBB (not 100% reproducible).

GDB:

[ RUN ] Core_Rand.parallel_for_stable_results [New Thread 0x7fffd46b7640 (LWP 232758)] [New Thread 0x7fffa8ffa640 (LWP 232760)] [New Thread 0x7fffb07f8640 (LWP 232759)] [ OK ] Core_Rand.parallel_for_stable_results (174 ms) ... [ INFO:0] global /home/alalek/projects/opencv/dev/modules/core/src/utils/plugin_loader.impl.hpp (50) libraryRelease unload /home/alalek/projects/opencv/build/opencv/lib/libopencv_core_parallel_onetbb.so Thread 34 "opencv_test_cor" received signal SIGSEGV, Segmentation fault. (gdb) info threads ... 33 Thread 0x7fffd46b7640 (LWP 232758) "opencv_test_cor" 0x00007ffff47ba55d in syscall () from /lib64/libc.so.6 * 34 Thread 0x7fffa8ffa640 (LWP 232760) "opencv_test_cor" 0x00007fffe749ba32 in ?? () 35 Thread 0x7fffb07f8640 (LWP 232759) "opencv_test_cor" 0x00007ffff47ba55d in syscall () from /lib64/libc.so.6

(232760 is created during the test run)

LD_DEBUG dump:

[ INFO:0] global /home/alalek/projects/opencv/dev/modules/core/src/utils/plugin_loader.impl.hpp (50) libraryRelease unload /home/alalek/projects/opencv/build/opencv/lib/libopencv_core_parallel_onetbb.so 232863: 232863: calling fini: /home/alalek/projects/opencv/build/opencv/lib/libopencv_core_parallel_onetbb.so [0] 232863: 232863: 232863: calling fini: /lib64/libtbb.so.2 [0] 232863: 232863: 232863: calling fini: /lib64/libirml.so.1 [0] 232863: Segmentation fault (core dumped)

TODO: Will try to check some workarounds.

Added code to prevent automatic unloading of parallel backend library (including underlying libraries).
There is no huge impact, because plugins are kept loaded until opencv_core unloading anyway.

alalek · 2021-02-15T17:11:00Z

modules/videoio/cmake/init.cmake

+# FIXIT: stop using PARENT_SCOPE in dependencies
+if(PROJECT_NAME STREQUAL "OpenCV")
+  macro(add_backend backend_id cond_var)
+    if(${cond_var})
+      include("${CMAKE_CURRENT_LIST_DIR}/detect_${backend_id}.cmake")
+    endif()
+  endmacro()
+else()
+  function(add_backend backend_id cond_var)
+    if(${cond_var})
+      include("${CMAKE_CURRENT_LIST_DIR}/detect_${backend_id}.cmake")
+    endif()
+  endfunction()
+endif()


There is inconsistency in scope of dependencies.

Perhaps we could switch to target checks instead of HAVE_ variables. Additional information can be stored in custom target properties.

cmake/OpenCVPluginStandalone.cmake

mshabunin self-assigned this Feb 9, 2021

mshabunin reviewed Feb 12, 2021

View reviewed changes

alalek commented Feb 12, 2021

View reviewed changes

core(parallel): plugins support

cc73c36

alalek commented Feb 15, 2021

View reviewed changes

mshabunin approved these changes Feb 16, 2021

View reviewed changes

opencv-pushbot merged commit 20d5d1c into opencv:master Feb 16, 2021

This was referenced Feb 19, 2021

cmake(plugins): build without opencv_*.so on OSX #19568

Merged

core(parallel): fix JS build, fix OpenMP version dump #19594

Merged

mshabunin mentioned this pull request Feb 24, 2021

Minor fixes to plugin compilation and VA feature #19610

Merged

This was referenced Mar 13, 2021

Cannot import cv2 due to issue with TBB #19725

Closed

core(parallel): fix plugins handling if no filesystem available #19747

Merged

alalek mentioned this pull request Apr 9, 2021

(5.x) Merge 4.x #19885

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core(parallel): plugins support#19470

core(parallel): plugins support#19470
opencv-pushbot merged 1 commit intoopencv:masterfrom
alalek:core_parallel_plugins

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		@@ -0,0 +1,60 @@
		function(ocv_create_builtin_core_parallel_plugin name target)

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alalek commented Feb 6, 2021 •

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