Message281565
The following script:
import multiprocessing
import os
def f():
pass
multiprocessing.Lock()
if __name__ == "__main__":
ctx = multiprocessing.get_context('forkserver')
# modname is the script's importable name (not "__main__")
modname = os.path.basename(__file__).split(".")[0]
ctx.set_forkserver_preload([modname])
proc = ctx.Process(target=f)
proc.start()
proc.join()
Fails with the following error:
Traceback (most recent call last):
File "/home/antoine/miniconda3/envs/dask35/lib/python3.5/multiprocessing/forkserver.py", line 178, in main
_serve_one(s, listener, alive_r, handler)
File "/home/antoine/miniconda3/envs/dask35/lib/python3.5/multiprocessing/forkserver.py", line 212, in _serve_one
code = spawn._main(child_r)
File "/home/antoine/miniconda3/envs/dask35/lib/python3.5/multiprocessing/spawn.py", line 115, in _main
prepare(preparation_data)
File "/home/antoine/miniconda3/envs/dask35/lib/python3.5/multiprocessing/spawn.py", line 221, in prepare
set_start_method(data['start_method'])
File "/home/antoine/miniconda3/envs/dask35/lib/python3.5/multiprocessing/context.py", line 231, in set_start_method
raise RuntimeError('context has already been set')
RuntimeError: context has already been set
This makes set_forkserver_preload() quite fragile if you preload any library that may create multiprocessing resources (such as locks) at the top level. |
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Date |
User |
Action |
Args |
2016-11-23 15:26:41 | pitrou | set | recipients:
+ pitrou, sbt, davin |
2016-11-23 15:26:41 | pitrou | set | messageid: <1479914801.47.0.114591938702.issue28779@psf.upfronthosting.co.za> |
2016-11-23 15:26:41 | pitrou | link | issue28779 messages |
2016-11-23 15:26:40 | pitrou | create | |
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