subprocess auto-reaps children

[yorick]

BPO	1214859
Nosy	@loewis

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2006-04-10.16:04:35.000>
created_at = <Date 2005-06-04.16:42:25.000>
labels = []
title = 'subprocess auto-reaps children'
updated_at = <Date 2006-04-10.16:04:35.000>
user = 'https://bugs.python.org/yorick'

bugs.python.org fields:

activity = <Date 2006-04-10.16:04:35.000>
actor = 'loewis'
assignee = 'astrand'
closed = True
closed_date = None
closer = None
components = ['None']
creation = <Date 2005-06-04.16:42:25.000>
creator = 'yorick'
dependencies = []
files = []
hgrepos = []
issue_num = 1214859
keywords = []
message_count = 3.0
messages = ['25486', '25487', '25488']
nosy_count = 4.0
nosy_names = ['loewis', 'astrand', 'yorick', 'awaters']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = None
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue1214859'
versions = []

[yorick]

The subprocess module automatically reaps child processes, by
maintaining a list of instances which is traversed each time a new
Popen instance is created.

Apparently this was originally intended to avoid large number of
zombie processes to accrete in the system if the programmer is
lazy and does not wait for them properly, but it can cause problems
when the programmer wants greater control. In particular, it's not
possible to use the pid from a subprocess.Popen instance, since it
may already have disappeared. For instance, it makes it difficult to
use os.wait() to wait for several child processes at the same time.

The solution is simple: Add an option that disables the auto-reaper
for a Popen instance. This makes everyone happy: existing code is
unaffected, the programmer who wants to control her processes
herself is allowed to do that, and the documentation is improved to
help avoiding a nasty bug.

A patch was posted to the patch tracker as number 1187312. I
suggest it for inclusion into the next release.

[awaters]

Logged In: YES
user_id=1418249

May want to add a lock in order that auto reaping can
happen in addition to the use of waitpid.

[loewis]

Logged In: YES
user_id=21627

Thanks for the report. This is now fixed in r45234.