[issue43832] asyncio + multiprocessing = core dump in sem_trywait
Kunal added the comment:
I was trying to reproduce the problem and can get the core dump to happen with
a smaller program as well -- it doesn't seem related to asyncio specifically
but seems to be a bug with multiprocessing.Event (or probably the primitives
inside it).
```
#!/usr/bin/env python
import time
import multiprocessing
def master_func(event) -> None:
print(f"Child: {event = }")
print(f"Child: {event.is_set() = }") # Crashes here with SIGSEGV in
sem_trywait
print("Completed")
if __name__ == "__main__":
event = multiprocessing.Event()
context_spawn = multiprocessing.get_context("spawn")
proc = context_spawn.Process(target=master_func, args=(event, ))
proc.start()
print(f"Parent: {event = }")
print(f"Parent: {event.is_set() = }")
proc.join()
```
Switching to fork instead of spawn bypasses the issue. Trying to dig into this
a little bit more.
--
nosy: +knl
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[issue43832] asyncio + multiprocessing = core dump in sem_trywait
Kunal added the comment:
Oh, it looks like it's because the context for the Event doesn't match when
created this way (the default context on linux is fork).
The problem goes away if the Event instance is created from the spawn context
-- specifically, patching dump_core.py
```
@@ -22,14 +22,13 @@ def master_func(space:dict) -> None:
if __name__ == "__main__":
-this_event = multiprocessing.Event()
+context_spawn = multiprocessing.get_context("spawn")
+this_event = context_spawn.Event()
this_space = dict(
this_event=this_event,
)
-context_spawn = multiprocessing.get_context("spawn")
-
master_proc = context_spawn.Process(
```
I think this can be closed; the incompatibility between contexts is also
documented at
https://docs.python.org/3/library/multiprocessing.html#multiprocessing.Lock,
thought it could be a little more explicit about potential segfaults.
> Note that objects related to one context may not be compatible with processes
> for a different context. In pait's berticular, locks created using the fork
> context cannot be passed to processes started using the spawn or forkserver
> start methods.
(Event uses a Lock under the hood)
--
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[issue26302] cookies module allows commas in keys
Kunal Grover added the comment: Hi, I am a newcomer here, I am interested to work on this issue. -- nosy: +Kunal Grover ___ Python tracker <http://bugs.python.org/issue26302> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue26296] colorys rgb_to_hls algorithm error
Kunal Grover added the comment: This isn't needed. We are taking modulus with 1.0, which already fixes negative values of h. -- nosy: +Kunal Grover ___ Python tracker <http://bugs.python.org/issue26296> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
