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Created on 2018-09-26 16:42 by calimeroteknik, last changed 2022-04-11 14:59 by admin. This issue is now closed.
| Files | ||||
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| File name | Uploaded | Description | Edit | |
| hang.py | calimeroteknik, 2018-09-26 16:42 | Make cpython hang or not on waitpid by insterting a print or sleep statement | ||
| except-out.py | calimeroteknik, 2018-09-26 16:43 | Make cpython forget a child process or not by inserting a print or sleep statement | ||
| Messages (5) | |||
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| msg326485 - (view) | Author: calimeroteknik (calimeroteknik) | Date: 2018-09-26 16:42 | |
When two processes are created and killed, the behaviour is different if print or sleep statements are inserted. It can also be random (different results executing the same program several times) on certain machines and versions of python. Attached two versions, one where the child process mysteriously disappears in the cpython interpreter, and another other one that raises ChildProcessError: [Errno 10] No child processes. This shows up with cpython, all versions I tested (3.7, 3.6, 3.5, 2.7). pypy is unaffected. |
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| msg326488 - (view) | Author: Antoine Pitrou (pitrou) *  |
Date: 2018-09-26 17:01 | |
I don't think hang.py is correct. If you launch a process using subprocess, the subprocess owns the child process. You should not call waitpid() or os.kill() separately. Also, since you don't keep a reference to the subprocess.Popen object, its destructor will run and may call waitpid() on the child process. Depending on when exactly the destructor runs, it can interfere with your own waitpid() call. |
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| msg326489 - (view) | Author: Antoine Pitrou (pitrou) * |
Date: 2018-09-26 17:01 | |
Those remarks apply to except-out.py, as well. |
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| msg326493 - (view) | Author: calimeroteknik (calimeroteknik) | Date: 2018-09-26 17:13 | |
So this is invalid library usage, we need to run .wait() on the Popen object. |
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| msg326496 - (view) | Author: Antoine Pitrou (pitrou) * |
Date: 2018-09-26 17:24 | |
Indeed! |
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| History | |||
|---|---|---|---|
| Date | User | Action | Args |
| 2022-04-11 14:59:06 | admin | set | github: 78994 |
| 2018-09-26 17:24:18 | pitrou | set | messages: + msg326496 |
| 2018-09-26 17:13:17 | calimeroteknik | set | status: open -> closed resolution: not a bug messages: + msg326493 stage: resolved |
| 2018-09-26 17:01:55 | pitrou | set | messages: + msg326489 |
| 2018-09-26 17:01:17 | pitrou | set | nosy:
+ gregory.p.smith, giampaolo.rodola messages: + msg326488 |
| 2018-09-26 16:43:09 | calimeroteknik | set | files: + except-out.py |
| 2018-09-26 16:42:21 | calimeroteknik | create | |