OS 3.3.12 crashes when spawning experiment process, "context has already been set"

martinc

Hi,

trying to resurrect OS on Arch Linux. Everything seems OK except that experiments won't run, "Python seems to have crashed". Console output below. Any help greatly appreciated!

Traceback (most recent call last):
 File "<string>", line 1, in <module>
 File "/usr/lib/python3.10/multiprocessing/spawn.py", line 116, in spawn_main
   exitcode = _main(fd, parent_sentinel)
 File "/usr/lib/python3.10/multiprocessing/spawn.py", line 125, in _main
   prepare(preparation_data)
 File "/usr/lib/python3.10/multiprocessing/spawn.py", line 236, in prepare
   _fixup_main_from_path(data['init_main_from_path'])
 File "/usr/lib/python3.10/multiprocessing/spawn.py", line 287, in _fixup_main_from_path
   main_content = runpy.run_path(main_path,
 File "/usr/lib/python3.10/runpy.py", line 289, in run_path
   return _run_module_code(code, init_globals, run_name,
 File "/usr/lib/python3.10/runpy.py", line 96, in _run_module_code
   _run_code(code, mod_globals, init_globals,
 File "/usr/lib/python3.10/runpy.py", line 86, in _run_code
   exec(code, run_globals)
 File "/usr/bin/opensesame", line 5, in <module>
   from libqtopensesame.__main__ import opensesame
 File "/usr/lib/python3.10/site-packages/libqtopensesame/__main__.py", line 29, in <module>
   multiprocessing.set_start_method('spawn')
 File "/usr/lib/python3.10/multiprocessing/context.py", line 243, in set_start_method
   raise RuntimeError('context has already been set')
RuntimeError: context has already been set

martinc

To follow up: This seems to be a consequence of running with python 3.8 or higher (Arch is on 3.10), see here for example.

A quick (and probably dangerous/unsatisfactory) fix is to change line 29 of /usr/lib/python3.nn/site-packages/libqtopensesame/__main__.py to read

multiprocessing.set_start_method('spawn', force=True)

which appears to solve the issue (not thoroughly tested yet though).