Using pyImport creates tons of thread and potentially a fork ?

[Clonkk]

I recently swapped to Ubuntu and evenr since I noticed that any program that uses pyImport create lots of threads (that are eventually closed) and somehow a fork ?

Here's code that reproduce :

import nimpy
when isMainModule:
  echo "Hello world"
  echo "------------------------------------------------"
  let np = pyImport("numpy")
  echo np.zeros([2, 2])
  echo "------------------------------------------------"

Compiled with nim cpp --stacktrace:on --debugger=native testfile.nim

Ran program with GDB here's the output :

GNU gdb (Ubuntu 9.2-0ubuntu1~20.04) 9.2
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License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
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Type "show copying" and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
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    <http://www.gnu.org/software/gdb/documentation/>.

For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from ./tensortest...
(gdb) r
Starting program: /home/rcaillaud/Workspace/playground/benchme/tensortest 
Hello world
------------------------------------------------
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/usr/lib/x86_64-linux-gnu/libthread_db.so.1".
[New Thread 0x7ffff37a6700 (LWP 94583)]
[New Thread 0x7ffff0fa5700 (LWP 94584)]
[New Thread 0x7ffff07a4700 (LWP 94585)]
[New Thread 0x7fffedfa3700 (LWP 94586)]
[New Thread 0x7fffe97a2700 (LWP 94587)]
[New Thread 0x7fffe6fa1700 (LWP 94588)]
[New Thread 0x7fffe47a0700 (LWP 94589)]
[New Thread 0x7fffe1f9f700 (LWP 94590)]
[New Thread 0x7fffdf79e700 (LWP 94591)]
[New Thread 0x7fffdcf9d700 (LWP 94592)]
[New Thread 0x7fffda79c700 (LWP 94593)]
[Thread 0x7fffda79c700 (LWP 94593) exited]
[Thread 0x7fffdcf9d700 (LWP 94592) exited]
[Thread 0x7fffdf79e700 (LWP 94591) exited]
[Thread 0x7fffe1f9f700 (LWP 94590) exited]
[Thread 0x7fffe47a0700 (LWP 94589) exited]
[Thread 0x7fffe6fa1700 (LWP 94588) exited]
[Thread 0x7fffe97a2700 (LWP 94587) exited]
[Thread 0x7fffedfa3700 (LWP 94586) exited]
[Thread 0x7ffff07a4700 (LWP 94585) exited]
[Thread 0x7ffff0fa5700 (LWP 94584) exited]
[Thread 0x7ffff37a6700 (LWP 94583) exited]
[Detaching after fork from child process 94594]
[[0. 0.]
 [0. 0.]]
------------------------------------------------
[Inferior 1 (process 94579) exited normally]

1) I don't understand why so many threads are created then destroyed (it seems it's as many as the core the CPU)

2) I don't understand why it creates a fork (as noted by the message [Detaching after fork from child process 94594])

[yglukhov]

nimpy doesn't spawn any threads nor forks iirc. Try breaking on pthread_create and see the stack trace.

[Clonkk]

It gives me this stacktrace :

#0  __pthread_create_2_1 (newthread=0x7ffff5cd5300 <blas_threads>, attr=0x0, start_routine=0x7ffff412bfb0 <blas_thread_server>, arg=0x0) at pthread_create.c:625
#1  0x00007ffff412c397 in blas_thread_init () from /usr/local/lib/python3.8/dist-packages/numpy/core/../../numpy.libs/libopenblasp-r0-2d23e62b.3.17.so
#2  0x00007ffff3f0607f in gotoblas_init () from /usr/local/lib/python3.8/dist-packages/numpy/core/../../numpy.libs/libopenblasp-r0-2d23e62b.3.17.so
#3  0x00007ffff7fe0b8a in ?? () from /lib64/ld-linux-x86-64.so.2
#4  0x00007ffff7fe0c91 in ?? () from /lib64/ld-linux-x86-64.so.2
#5  0x00007ffff7d1e915 in _dl_catch_exception () from /usr/lib/x86_64-linux-gnu/libc.so.6
#6  0x00007ffff7fe50bf in ?? () from /lib64/ld-linux-x86-64.so.2
#7  0x00007ffff7d1e8b8 in _dl_catch_exception () from /usr/lib/x86_64-linux-gnu/libc.so.6
#8  0x00007ffff7fe45fa in ?? () from /lib64/ld-linux-x86-64.so.2
#9  0x00007ffff7fab34c in ?? () from /usr/lib/x86_64-linux-gnu/libdl.so.2
#10 0x00007ffff7d1e8b8 in _dl_catch_exception () from /usr/lib/x86_64-linux-gnu/libc.so.6
#11 0x00007ffff7d1e983 in _dl_catch_error () from /usr/lib/x86_64-linux-gnu/libc.so.6
#12 0x00007ffff7fabb59 in ?? () from /usr/lib/x86_64-linux-gnu/libdl.so.2
#13 0x00007ffff7fab3da in dlopen () from /usr/lib/x86_64-linux-gnu/libdl.so.2
#14 0x00007ffff7601833 in _PyImport_FindSharedFuncptr () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#15 0x00007ffff7638050 in _PyImport_LoadDynamicModuleWithSpec () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#16 0x00007ffff763a105 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#17 0x00007ffff76f0527 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#18 0x00007ffff7739810 in PyVectorcall_Call () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#19 0x00007ffff750ef48 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#20 0x00007ffff765becb in _PyEval_EvalCodeWithName () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#21 0x00007ffff77390f4 in _PyFunction_Vectorcall () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#22 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#23 0x00007ffff750def6 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#24 0x00007ffff751106b in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#25 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#26 0x00007ffff7507018 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#27 0x00007ffff751106b in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#28 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#29 0x00007ffff750746d in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#30 0x00007ffff751106b in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#31 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#32 0x00007ffff750746d in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#33 0x00007ffff751106b in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#34 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#35 0x00007ffff750746d in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#36 0x00007ffff751106b in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#37 0x00007ffff773a0c8 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#38 0x00007ffff773a320 in _PyObject_CallMethodIdObjArgs () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#39 0x00007ffff7519c1e in PyImport_ImportModuleLevelObject () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#40 0x00007ffff750d941 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#41 0x00007ffff765becb in _PyEval_EvalCodeWithName () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#42 0x00007ffff765c252 in PyEval_EvalCodeEx () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#43 0x00007ffff765c63f in PyEval_EvalCode () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#44 0x00007ffff7660c81 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#45 0x00007ffff76f0527 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#46 0x00007ffff7739810 in PyVectorcall_Call () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#47 0x00007ffff750ef48 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#48 0x00007ffff765becb in _PyEval_EvalCodeWithName () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#49 0x00007ffff77390f4 in _PyFunction_Vectorcall () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#50 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#51 0x00007ffff750def6 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#52 0x00007ffff751106b in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#53 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#54 0x00007ffff7507018 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#55 0x00007ffff751106b in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#56 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#57 0x00007ffff750746d in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#58 0x00007ffff751106b in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#59 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#60 0x00007ffff750746d in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#61 0x00007ffff751106b in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#62 0x00007ffff773a0c8 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#63 0x00007ffff773a320 in _PyObject_CallMethodIdObjArgs () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#64 0x00007ffff7519c1e in PyImport_ImportModuleLevelObject () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#65 0x00007ffff765f04e in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#66 0x00007ffff7739718 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#67 0x00007ffff750ef48 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#68 0x00007ffff765becb in _PyEval_EvalCodeWithName () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#69 0x00007ffff77390f4 in _PyFunction_Vectorcall () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#70 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#71 0x00007ffff750746d in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#72 0x00007ffff765becb in _PyEval_EvalCodeWithName () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#73 0x00007ffff77390f4 in _PyFunction_Vectorcall () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#74 0x00007ffff773a0c8 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#75 0x00007ffff773a320 in _PyObject_CallMethodIdObjArgs () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#76 0x00007ffff7519e6a in PyImport_ImportModuleLevelObject () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#77 0x00007ffff750d941 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#78 0x00007ffff765becb in _PyEval_EvalCodeWithName () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#79 0x00007ffff765c252 in PyEval_EvalCodeEx () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#80 0x00007ffff765c63f in PyEval_EvalCode () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#81 0x00007ffff7660c81 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#82 0x00007ffff76f0527 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#83 0x00007ffff7739810 in PyVectorcall_Call () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#84 0x00007ffff750ef48 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#85 0x00007ffff765becb in _PyEval_EvalCodeWithName () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#86 0x00007ffff77390f4 in _PyFunction_Vectorcall () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#87 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#88 0x00007ffff750def6 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#89 0x00007ffff751106b in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#90 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#91 0x00007ffff7507018 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#92 0x00007ffff751106b in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#93 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#94 0x00007ffff750746d in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#95 0x00007ffff751106b in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#96 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#97 0x00007ffff750746d in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#98 0x00007ffff751106b in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#99 0x00007ffff773a0c8 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#100 0x00007ffff773a320 in _PyObject_CallMethodIdObjArgs () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#101 0x00007ffff7519c1e in PyImport_ImportModuleLevelObject () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#102 0x00007ffff765f04e in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#103 0x00007ffff7739718 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#104 0x00007ffff750ef48 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#105 0x00007ffff765becb in _PyEval_EvalCodeWithName () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#106 0x00007ffff77390f4 in _PyFunction_Vectorcall () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#107 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
--Type <RET> for more, q to quit, c to continue without paging--
#108 0x00007ffff750746d in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#109 0x00007ffff765becb in _PyEval_EvalCodeWithName () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#110 0x00007ffff77390f4 in _PyFunction_Vectorcall () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#111 0x00007ffff773a0c8 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#112 0x00007ffff773a320 in _PyObject_CallMethodIdObjArgs () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#113 0x00007ffff7519e6a in PyImport_ImportModuleLevelObject () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#114 0x00007ffff750d941 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#115 0x00007ffff765becb in _PyEval_EvalCodeWithName () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#116 0x00007ffff765c252 in PyEval_EvalCodeEx () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#117 0x00007ffff765c63f in PyEval_EvalCode () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#118 0x00007ffff7660c81 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#119 0x00007ffff76f0527 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#120 0x00007ffff7739810 in PyVectorcall_Call () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#121 0x00007ffff750ef48 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#122 0x00007ffff765becb in _PyEval_EvalCodeWithName () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#123 0x00007ffff77390f4 in _PyFunction_Vectorcall () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#124 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#125 0x00007ffff750def6 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#126 0x00007ffff751106b in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#127 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#128 0x00007ffff7507018 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#129 0x00007ffff751106b in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#130 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#131 0x00007ffff750746d in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#132 0x00007ffff751106b in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#133 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#134 0x00007ffff750746d in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#135 0x00007ffff751106b in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#136 0x00007ffff773a0c8 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#137 0x00007ffff773a320 in _PyObject_CallMethodIdObjArgs () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#138 0x00007ffff7519c1e in PyImport_ImportModuleLevelObject () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#139 0x00007ffff765f04e in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#140 0x00007ffff7739718 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#141 0x00007ffff750ef48 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#142 0x00007ffff765becb in _PyEval_EvalCodeWithName () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#143 0x00007ffff77390f4 in _PyFunction_Vectorcall () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#144 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#145 0x00007ffff750746d in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#146 0x00007ffff765becb in _PyEval_EvalCodeWithName () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#147 0x00007ffff77390f4 in _PyFunction_Vectorcall () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#148 0x00007ffff773a0c8 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#149 0x00007ffff773a320 in _PyObject_CallMethodIdObjArgs () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#150 0x00007ffff7519e6a in PyImport_ImportModuleLevelObject () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#151 0x00007ffff750d941 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#152 0x00007ffff765becb in _PyEval_EvalCodeWithName () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#153 0x00007ffff765c252 in PyEval_EvalCodeEx () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#154 0x00007ffff765c63f in PyEval_EvalCode () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#155 0x00007ffff7660c81 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#156 0x00007ffff76f0527 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#157 0x00007ffff7739810 in PyVectorcall_Call () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#158 0x00007ffff750ef48 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#159 0x00007ffff765becb in _PyEval_EvalCodeWithName () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#160 0x00007ffff77390f4 in _PyFunction_Vectorcall () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#161 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
--Type <RET> for more, q to quit, c to continue without paging--
#162 0x00007ffff750def6 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#163 0x00007ffff751106b in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#164 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#165 0x00007ffff7507018 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#166 0x00007ffff751106b in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#167 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#168 0x00007ffff750746d in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#169 0x00007ffff751106b in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#170 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#171 0x00007ffff750746d in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#172 0x00007ffff751106b in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#173 0x00007ffff773a0c8 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#174 0x00007ffff773a320 in _PyObject_CallMethodIdObjArgs () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#175 0x00007ffff7519c1e in PyImport_ImportModuleLevelObject () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#176 0x00007ffff765f04e in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#177 0x00007ffff7739718 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#178 0x00007ffff7739afb in _PyObject_MakeTpCall () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#179 0x00007ffff7739f82 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#180 0x00007ffff773b15f in PyObject_CallFunction () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#181 0x00007ffff7636c80 in PyImport_Import () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#182 0x00007ffff7636e7e in PyImport_ImportModule () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#183 0x0000555555582905 in pyImport_OOZOOZlocalwsZnimpyZnimpy_1397 (moduleName=0x555555587442 "numpy") at /home/rcaillaud/Workspace/localws/nimpy/nimpy.nim:934
#184 0x00005555555842f0 in NimMainModule () at /home/rcaillaud/Workspace/playground/benchme/tensortest.nim:43
#185 0x0000555555584d13 in NimMainInner () at /home/rcaillaud/.choosenim/toolchains/nim-1.6.0/lib/system.nim:2234
#186 0x00005555555841c0 in NimMain () at /home/rcaillaud/.choosenim/toolchains/nim-1.6.0/lib/system.nim:2242
#187 0x00005555555841f7 in main (argc=<optimized out>, args=<optimized out>, env=<optimized out>) at /home/rcaillaud/.choosenim/toolchains/nim-1.6.0/lib/system.nim:2249

So it looks like it's internal to libpython.The threads looks to be BLAS related (which would make sense since I import numpy) but the fork that appears to be created worries more.

[yglukhov]

Yep, looks like it's BLAS, which is used by numpy indeed. You can debug fork in the same way.

[Clonkk]

It goes direactly to libpython -> libc;

#0  0x00007ffff7ca1070 in fork () from /usr/lib/x86_64-linux-gnu/libc.so.6
#1  0x00007ffff75c12bf in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#2  0x00007ffff7739667 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#3  0x00007ffff7739afb in _PyObject_MakeTpCall () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#4  0x00007ffff7505df3 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#5  0x00007ffff750def6 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#6  0x00007ffff765becb in _PyEval_EvalCodeWithName () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#7  0x00007ffff77390f4 in _PyFunction_Vectorcall () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#8  0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#9  0x00007ffff7507018 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#10 0x00007ffff765becb in _PyEval_EvalCodeWithName () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#11 0x00007ffff77390f4 in _PyFunction_Vectorcall () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#12 0x00007ffff773b379 in _PyObject_FastCallDict () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#13 0x00007ffff773b4fd in _PyObject_Call_Prepend () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#14 0x00007ffff76d4d27 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#15 0x00007ffff76da199 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#16 0x00007ffff7739964 in PyObject_Call () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#17 0x00007ffff750ba7a in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#18 0x00007ffff765becb in _PyEval_EvalCodeWithName () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#19 0x00007ffff77390f4 in _PyFunction_Vectorcall () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#20 0x00007ffff7739810 in PyVectorcall_Call () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#21 0x00007ffff750ba7a in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#22 0x00007ffff765becb in _PyEval_EvalCodeWithName () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#23 0x00007ffff77390f4 in _PyFunction_Vectorcall () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#24 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#25 0x00007ffff750a713 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#26 0x00007ffff765becb in _PyEval_EvalCodeWithName () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#27 0x00007ffff77390f4 in _PyFunction_Vectorcall () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#28 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#29 0x00007ffff750746d in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#30 0x00007ffff751106b in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#31 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#32 0x00007ffff750746d in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#33 0x00007ffff751106b in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#34 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#35 0x00007ffff750def6 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#36 0x00007ffff77282b4 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#37 0x00007ffff7718776 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#38 0x00007ffff7750d0d in PySequence_List () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#39 0x00007ffff77511c2 in PySequence_Fast () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#40 0x00007ffff76b074d in PyUnicode_Join () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#41 0x00007ffff773208d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#42 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#43 0x00007ffff7507018 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#44 0x00007ffff765becb in _PyEval_EvalCodeWithName () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#45 0x00007ffff77390f4 in _PyFunction_Vectorcall () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#46 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#47 0x00007ffff750746d in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#48 0x00007ffff765becb in _PyEval_EvalCodeWithName () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#49 0x00007ffff765c252 in PyEval_EvalCodeEx () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#50 0x00007ffff765c63f in PyEval_EvalCode () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#51 0x00007ffff7660c81 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#52 0x00007ffff76f0527 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#53 0x00007ffff7739810 in PyVectorcall_Call () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
--Type <RET> for more, q to quit, c to continue without paging--c
#54 0x00007ffff750ef48 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#55 0x00007ffff765becb in _PyEval_EvalCodeWithName () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#56 0x00007ffff77390f4 in _PyFunction_Vectorcall () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#57 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#58 0x00007ffff750def6 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#59 0x00007ffff751106b in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#60 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#61 0x00007ffff7507018 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#62 0x00007ffff751106b in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#63 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#64 0x00007ffff750746d in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#65 0x00007ffff751106b in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#66 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#67 0x00007ffff750746d in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#68 0x00007ffff751106b in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#69 0x00007ffff773a0c8 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#70 0x00007ffff773a320 in _PyObject_CallMethodIdObjArgs () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#71 0x00007ffff7519c1e in PyImport_ImportModuleLevelObject () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#72 0x00007ffff765f04e in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#73 0x00007ffff7739718 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#74 0x00007ffff750ef48 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#75 0x00007ffff765becb in _PyEval_EvalCodeWithName () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#76 0x00007ffff77390f4 in _PyFunction_Vectorcall () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#77 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#78 0x00007ffff750746d in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#79 0x00007ffff765becb in _PyEval_EvalCodeWithName () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#80 0x00007ffff77390f4 in _PyFunction_Vectorcall () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#81 0x00007ffff773a0c8 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#82 0x00007ffff773a320 in _PyObject_CallMethodIdObjArgs () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#83 0x00007ffff7519e6a in PyImport_ImportModuleLevelObject () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#84 0x00007ffff750d941 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#85 0x00007ffff765becb in _PyEval_EvalCodeWithName () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#86 0x00007ffff765c252 in PyEval_EvalCodeEx () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#87 0x00007ffff765c63f in PyEval_EvalCode () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#88 0x00007ffff7660c81 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#89 0x00007ffff76f0527 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#90 0x00007ffff7739810 in PyVectorcall_Call () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#91 0x00007ffff750ef48 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#92 0x00007ffff765becb in _PyEval_EvalCodeWithName () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#93 0x00007ffff77390f4 in _PyFunction_Vectorcall () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#94 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#95 0x00007ffff750def6 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#96 0x00007ffff751106b in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#97 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#98 0x00007ffff7507018 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#99 0x00007ffff751106b in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#100 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#101 0x00007ffff750746d in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#102 0x00007ffff751106b in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#103 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#104 0x00007ffff750746d in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#105 0x00007ffff751106b in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#106 0x00007ffff773a0c8 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#107 0x00007ffff773a320 in _PyObject_CallMethodIdObjArgs () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#108 0x00007ffff7519c1e in PyImport_ImportModuleLevelObject () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#109 0x00007ffff765f04e in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#110 0x00007ffff7739718 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#111 0x00007ffff750ef48 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#112 0x00007ffff765becb in _PyEval_EvalCodeWithName () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#113 0x00007ffff77390f4 in _PyFunction_Vectorcall () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#114 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#115 0x00007ffff750746d in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#116 0x00007ffff765becb in _PyEval_EvalCodeWithName () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#117 0x00007ffff77390f4 in _PyFunction_Vectorcall () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#118 0x00007ffff773a0c8 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#119 0x00007ffff773a320 in _PyObject_CallMethodIdObjArgs () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#120 0x00007ffff7519e6a in PyImport_ImportModuleLevelObject () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#121 0x00007ffff750d941 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#122 0x00007ffff765becb in _PyEval_EvalCodeWithName () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#123 0x00007ffff765c252 in PyEval_EvalCodeEx () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#124 0x00007ffff765c63f in PyEval_EvalCode () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#125 0x00007ffff7660c81 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#126 0x00007ffff76f0527 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#127 0x00007ffff7739810 in PyVectorcall_Call () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#128 0x00007ffff750ef48 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#129 0x00007ffff765becb in _PyEval_EvalCodeWithName () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#130 0x00007ffff77390f4 in _PyFunction_Vectorcall () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#131 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#132 0x00007ffff750def6 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#133 0x00007ffff751106b in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#134 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#135 0x00007ffff7507018 in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#136 0x00007ffff751106b in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#137 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#138 0x00007ffff750746d in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#139 0x00007ffff751106b in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#140 0x00007ffff7505d6d in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#141 0x00007ffff750746d in _PyEval_EvalFrameDefault () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#142 0x00007ffff751106b in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#143 0x00007ffff773a0c8 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#144 0x00007ffff773a320 in _PyObject_CallMethodIdObjArgs () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#145 0x00007ffff7519c1e in PyImport_ImportModuleLevelObject () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#146 0x00007ffff765f04e in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#147 0x00007ffff7739718 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#148 0x00007ffff7739afb in _PyObject_MakeTpCall () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#149 0x00007ffff7739f82 in ?? () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#150 0x00007ffff773b15f in PyObject_CallFunction () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#151 0x00007ffff7636c80 in PyImport_Import () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#152 0x00007ffff7636e7e in PyImport_ImportModule () from /usr/lib/x86_64-linux-gnu/libpython3.8.so
#153 0x0000555555582905 in pyImport_OOZOOZlocalwsZnimpyZnimpy_1397 (moduleName=0x555555587442 "numpy") at /home/rcaillaud/Workspace/localws/nimpy/nimpy.nim:934
#154 0x00005555555842f0 in NimMainModule () at /home/rcaillaud/Workspace/playground/benchme/tensortest.nim:43
#155 0x0000555555584d13 in NimMainInner () at /home/rcaillaud/.choosenim/toolchains/nim-1.6.0/lib/system.nim:2234
#156 0x00005555555841c0 in NimMain () at /home/rcaillaud/.choosenim/toolchains/nim-1.6.0/lib/system.nim:2242
#157 0x00005555555841f7 in main (argc=<optimized out>, args=<optimized out>, env=<optimized out>) at /home/rcaillaud/.choosenim/toolchains/nim-1.6.0/lib/system.nim:2249

Which doesn't make sense since I don't create any fork

[yglukhov]

It's happening in pyImport("numpy"), so I guess numpy does that. You could also debug python -c "import numpy" and see if it happens. In any case, I doubt I can be of any help here.