[issue31173] test_subprocess: test_child_terminated_in_stopped_state() leaks a zombie process

[STINNER Victor]

STINNER Victor added the comment:


New changeset 4dea06531ece28dffc1452de2694fb22e99b45f9 by Victor Stinner in 
branch '2.7':
bpo-31173: Rewrite WSTOPSIG test of test_subprocess (#3055) (#3071)
https://github.com/python/cpython/commit/4dea06531ece28dffc1452de2694fb22e99b45f9


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[issue31173] test_subprocess: test_child_terminated_in_stopped_state() leaks a zombie process

[STINNER Victor]

Changes by STINNER Victor :


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resolution:  -> fixed
stage:  -> resolved
status: open -> closed

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[issue31173] test_subprocess: test_child_terminated_in_stopped_state() leaks a zombie process

[STINNER Victor]

Changes by STINNER Victor :


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pull_requests: +3107

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[issue31173] test_subprocess: test_child_terminated_in_stopped_state() leaks a zombie process

[STINNER Victor]

STINNER Victor added the comment:

Reopen. I forgot Python 2.7.

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[issue31173] test_subprocess: test_child_terminated_in_stopped_state() leaks a zombie process

[STINNER Victor]

STINNER Victor added the comment:


New changeset bc69d00288a0b1f5ef49dcfd60a91c5e9b5b81ae by Victor Stinner in 
branch '3.6':
bpo-31173: Rewrite WSTOPSIG test of test_subprocess (#3055) (#3070)
https://github.com/python/cpython/commit/bc69d00288a0b1f5ef49dcfd60a91c5e9b5b81ae


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[issue31173] test_subprocess: test_child_terminated_in_stopped_state() leaks a zombie process

[STINNER Victor]

Changes by STINNER Victor :


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pull_requests: +3106

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[issue31173] test_subprocess: test_child_terminated_in_stopped_state() leaks a zombie process

[STINNER Victor]

STINNER Victor added the comment:


New changeset 7b7c6dcfff6a35333988a3c74c895ed19dff2e09 by Victor Stinner in 
branch 'master':
bpo-31173: Rewrite WSTOPSIG test of test_subprocess (#3055)
https://github.com/python/cpython/commit/7b7c6dcfff6a35333988a3c74c895ed19dff2e09


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[issue31173] test_subprocess: test_child_terminated_in_stopped_state() leaks a zombie process

[STINNER Victor]

STINNER Victor added the comment:

I chose to only add W_STOPCODE() to _testcapi rather than the os module, 
because I don't want to have to document this function. I don't think that 
anyone needs such function, usually we only need to consume process statuses, 
not to produce them. The only use case is to write an unit test.

This issue is part of bpo-31160 which ensures that unit tests don't leak child 
processes. This issue is part of my large project of reducing the fail rate on 
CIs (Travis CI, AppVeyor, buildbots):
https://haypo.github.io/python-buildbots-2017q2.html

I will now merge my PR 3055 to be able to unblock my work on CIs. But I will 
wait for feedback from Gregory before backporting this fix to 2.7 and 3.6.

--
nosy: +gregory.p.smith
versions: +Python 2.7, Python 3.6

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[issue31173] test_subprocess: test_child_terminated_in_stopped_state() leaks a zombie process

[STINNER Victor]

STINNER Victor added the comment:

https://github.com/python/cpython/pull/3055 removes the functional test and 
replaces it with an unit test which mocks os.waitpid() using a new 
_testcapi.W_STOPCODE() function to test the WIFSTOPPED() path.

The functional test created a core dump, but it's now fixed using 
SuppressCrashReport. It leaks a zombie process in a special state, the process 
is traced and cannot be killed. I tried to wait for the process a second time, 
but it's not enough to "close" it. I guess that we would have to write a little 
debugger to attach the process in the parent process. IMHO it's overcomplicated 
just to check that subprocess calls WIFSTOPPED().

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[issue31173] test_subprocess: test_child_terminated_in_stopped_state() leaks a zombie process

[STINNER Victor]

Changes by STINNER Victor :


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pull_requests: +3090

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[issue31173] test_subprocess: test_child_terminated_in_stopped_state() leaks a zombie process

[STINNER Victor]

New submission from STINNER Victor:

The test_child_terminated_in_stopped_state() test creates a child process which 
calls ptrace(PTRACE_ME, 0, 0) and then crashs using SIGSEGV. The problem is 
that even if we read the exit status using os.waitpid() through subprocess, the 
process remains alive in the "t (tracing stop)" state.

I would prefer to not use ptrace() is an unit test since this API is very 
low-level and it's hard to use it correctly.

I suggest to either remove the functional test, or to rewrite it as an unit 
test using mocks to test bpo-29335 without ptrace().

haypo@selma$ ./python -m test -m test_child_terminated_in_stopped_state -F 
test_subprocess
Run tests sequentially
0:00:00 load avg: 0.95 [  1] test_subprocess
0:00:00 load avg: 0.95 [  2] test_subprocess
0:00:01 load avg: 0.96 [  3] test_subprocess
0:00:01 load avg: 0.96 [  4] test_subprocess
0:00:02 load avg: 0.96 [  5] test_subprocess
0:00:03 load avg: 0.96 [  6] test_subprocess
0:00:03 load avg: 0.96 [  7] test_subprocess
0:00:04 load avg: 0.96 [  8] test_subprocess
0:00:05 load avg: 0.96 [  9] test_subprocess
0:00:05 load avg: 0.96 [ 10] test_subprocess
^Z
[1]+  Stoppé ./python -m test -m 
test_child_terminated_in_stopped_state -F test_subprocess

haypo@selma$ ps
  PID TTY  TIME CMD
30359 pts/000:00:00 bash
31882 pts/000:00:00 python
31885 pts/000:00:00 python
31888 pts/000:00:00 python
31892 pts/000:00:00 python
31895 pts/000:00:00 python
31898 pts/000:00:00 python
31901 pts/000:00:00 python
31904 pts/000:00:00 python
31907 pts/000:00:00 python
31910 pts/000:00:00 python
31912 pts/000:00:00 python
31920 pts/000:00:00 ps

haypo@selma$ grep Stat /proc/31885/status
State:  t (tracing stop)

--
messages: 300066
nosy: haypo
priority: normal
severity: normal
status: open
title: test_subprocess: test_child_terminated_in_stopped_state() leaks a zombie 
process

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[issue31173] test_subprocess: test_child_terminated_in_stopped_state() leaks a zombie process

[STINNER Victor]

Changes by STINNER Victor :


--
components: +Tests
versions: +Python 3.7

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