koobs added the comment:
For reference, this test is successfuly identifying failures on koobs-freebsd
and koobs-freebsd10 buildbots:
==
FAIL: test_is_alive_after_fork (test.test_threading.ThreadTests)
Antoine Pitrou added the comment:
I've identified a possible cause (and fix) for the sporadic test failures in
74dc664ad699. If the solution holds, it should be backported to 3.3 and 2.7.
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Charles-François Natali added the comment:
The final patch includes tests that are very reliable at
revealing the bug in 2.7 and 3.3.
Indeed, I could reproduce it systematically without the patch.
Thanks for accepting this patch!
Well, thanks for the patch!
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resolution: - fixed
Changes by Charles-François Natali cf.nat...@gmail.com:
--
nosy: +pitrou
stage: patch review - commit review
versions: +Python 3.3, Python 3.4
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Antoine Pitrou added the comment:
Well... I can't say anything except that the patch looks harmless.
It's a pity the test failure is hard to trigger, though.
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Roundup Robot added the comment:
New changeset ba54011aa295 by Charles-François Natali in branch '2.7':
Issue #18418: After fork(), reinit all threads states, not only active ones.
http://hg.python.org/cpython/rev/ba54011aa295
New changeset 29fce7f31539 by Charles-François Natali in branch
A. Jesse Jiryu Davis added the comment:
Thanks for accepting this patch!
Antoine, I initially had trouble writing a test that reliably reproduced the
bug, especially in Python 3.3. But I read other threading tests and got
smarter. The final patch includes tests that are very reliable at
Changes by Charles-François Natali cf.nat...@gmail.com:
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stage: - patch review
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A. Jesse Jiryu Davis added the comment:
FYI I'm going on vacation again 8/20 through 8/25. I'll check in again as soon
as I return to see if there's anything else I should do.
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Python tracker rep...@bugs.python.org
A. Jesse Jiryu Davis added the comment:
Bump.
I think my most recent patch (August 4) addresses all of Charles-François's
comments.
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A. Jesse Jiryu Davis added the comment:
I'm back from a Zen retreat--no email!--will address your comments
momentarily.
On Fri, Aug 2, 2013 at 3:07 AM, Charles-François Natali
rep...@bugs.python.org wrote:
Charles-François Natali added the comment:
I've posted another review (not sure you
A. Jesse Jiryu Davis added the comment:
New patch for 3.3 branch after Charles-François's critique: use _enumerate()
where appropriate, and join the test thread before finishing the test.
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Added file: http://bugs.python.org/file31153/issue18418-3.patch
Charles-François Natali added the comment:
I've posted another review (not sure you receive notifications).
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A. Jesse Jiryu Davis added the comment:
By the way, I'm going on vacation through August 4. When I return I'll
check if there's anything else I need to do to help resolve this.
On Thursday, July 25, 2013, A. Jesse Jiryu Davis wrote:
A. Jesse Jiryu Davis added the comment:
(Sorry about the
Charles-François Natali added the comment:
Bump.
Did you see my review at http://bugs.python.org/review/18418/#ps8668 ?
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A. Jesse Jiryu Davis added the comment:
Oh, no I didn't. I'm learning how this system works. I'll respond there
soon.
Thanks
On Thursday, July 25, 2013, Charles-François Natali wrote:
Charles-François Natali added the comment:
Bump.
Did you see my review at
A. Jesse Jiryu Davis added the comment:
New patch for 3.3 branch after Charles-François's critique: instead of changing
startup sequence in Thread._bootstrap_inner, stop all threads in _limbo after a
fork.
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Added file: http://bugs.python.org/file31035/issue18418-2.patch
A. Jesse Jiryu Davis added the comment:
(Sorry about the extraneous XML file from my IDE, I made a mistake and allowed
the diff to include it.)
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A. Jesse Jiryu Davis added the comment:
Bump.
--
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A. Jesse Jiryu Davis added the comment:
Charles-François, I agree that many guarantees are impossible to enforce in a
multithreaded application that calls fork().
But the threading module does try to guarantee, after a fork, that isAlive() is
False for all threads but one. I claim that it can
Gregory P. Smith added the comment:
This patch makes sense to me. I've gone over the code and I cannot spot any
adverse effects. I was wondering in particular if anything would be surprised
to find a non-started thread in _active within the short window where that will
be true but nothing
Charles-François Natali added the comment:
If you want a consistent reproducible test case for this I believe you will
need to replace the Thread object's __started with a test wrapper who's set()
method blocks waiting for for the fork to have happened before doing the
actual set(). That
A. Jesse Jiryu Davis added the comment:
Patch #2:
* Add comment before .set() as requested.
* setcheckinterval(0) and try 20 times to repro the bug, inspired by
test_enumerate_after_join. This reliably repros in 2.7.5.
--
Added file:
Changes by A. Jesse Jiryu Davis je...@emptysquare.net:
Added file:
http://bugs.python.org/file30935/fix_is_alive_and_fork_python_33.patch
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Charles-François Natali added the comment:
This is just a special-case of the more general problem of forking() in a
multi-threaded program (see #16500 and #6721).
Since fork() can occur at any time, even though your data structures are
protected by locks, they can end up in an inconsistent
New submission from A. Jesse Jiryu Davis:
In threading.Thread.__bootstrap_inner(), the thread sets self.__started before
adding itself to the _active collection. If a different thread forks between
these two operations, we're left with a thread that believes it's alive
although it isn't.
Changes by Antoine Pitrou pit...@free.fr:
--
nosy: +gregory.p.smith, sbt
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