[issue13812] multiprocessing package doesn't flush stderr on child exception

Memeplex added the comment: http://bugs.python.org/issue24948 I posted a tentative solution there. -- ___ Python tracker ___ ___ Pyth

[issue13812] multiprocessing package doesn't flush stderr on child exception

R. David Murray added the comment: You should open a new issue. Bonus if you can supply a unit test and patch :) -- nosy: +r.david.murray ___ Python tracker ___

[issue13812] multiprocessing package doesn't flush stderr on child exception

Changes by Memeplex : -- versions: +Python 3.4, Python 3.5 ___ Python tracker ___ ___ Python-bugs-list mailing list Unsubscribe: http

[issue13812] multiprocessing package doesn't flush stderr on child exception

Memeplex added the comment: I would like to reopen this issue because of the following, very related, behavior. Try this: ``` import multiprocessing as mp import time def g(): time.sleep(100) def f(): mp.Process(target=g).start() 1/0 mp.Process(target=f).start() ``` It won't sh

[issue13812] multiprocessing package doesn't flush stderr on child exception

Antoine Pitrou added the comment: Patch now committed, thanks. -- resolution: -> fixed stage: patch review -> committed/rejected status: open -> closed ___ Python tracker ___ _

[issue13812] multiprocessing package doesn't flush stderr on child exception

Roundup Robot added the comment: New changeset 2863d9273abd by Antoine Pitrou in branch '3.2': Issue #13812: When a multiprocessing Process child raises an exception, flush stderr after printing the exception traceback. http://hg.python.org/cpython/rev/2863d9273abd New changeset 96c1de5acbd3 b

[issue13812] multiprocessing package doesn't flush stderr on child exception

Jon Brandvein added the comment: Patch looks fine. I like the use of "finally" for the flush. -- ___ Python tracker ___ ___ Python-bu

[issue13812] multiprocessing package doesn't flush stderr on child exception

Charles-François Natali added the comment: LGTM. (I just noticed a bug in Rietveld: when one selects "expand 10 after", the line right after that marker appears duplicated in the new view). -- ___ Python tracker

[issue13812] multiprocessing package doesn't flush stderr on child exception

Antoine Pitrou added the comment: Updated patch sanitizing the various flushes done on exit, as per Charles-François's recommendation. Also removes TESTFN explicitly. -- Added file: http://bugs.python.org/file24311/mpstderrflush2.patch ___ Python tr

[issue13812] multiprocessing package doesn't flush stderr on child exception

Charles-François Natali added the comment: > I propose applying the following patch. The test looks good to me (except we don't remove TESTFN explicitely, but I'm not sure it's really necessary). As for the patch, couldn't we put all the file stream flushing in one place? stdout and stderr ar

[issue13812] multiprocessing package doesn't flush stderr on child exception

Jesse Noller added the comment: There's already a bug / pending patch for this behavior here: http://bugs.python.org/issue8713 No need to take it to -ideas. -- ___ Python tracker

[issue13812] multiprocessing package doesn't flush stderr on child exception

Jon Brandvein added the comment: Regarding the patch: I'd also like to see sys.stdout.flush() and sys.stderr.flush() between "exitcode = self._boostrap()" and "exit(exitcode)" in /Lib/multiprocessing/forking.py :: main(). (The extra stderr flush would be for symmetry with Popen.__init__() for

[issue13812] multiprocessing package doesn't flush stderr on child exception

Antoine Pitrou added the comment: I propose applying the following patch. We could open a separate issue to suggest "exit = sys.exit" under Windows (it doesn't seem to break any tests). -- keywords: +patch nosy: +neologix stage: test needed -> patch review Added file: http://bugs.pytho

[issue13812] multiprocessing package doesn't flush stderr on child exception

Antoine Pitrou added the comment: > I also found that under Python 2.x, even a low-level exit like > os._exit or multiprocessing.win32.ExitProcess, called from within a > user-level function in the child, caused flushing. The difference is the following: - Python 2.x uses C stdio (write() calls

[issue13812] multiprocessing package doesn't flush stderr on child exception

Jon Brandvein added the comment: It turns out the file output was flushing due to garbage collection. When I created and held a global reference to it, it ceased to flush. Clearly, reassigning sys.stdout also held a reference to it. So it wasn't any kind of special sys.stdout-specific logic.

[issue13812] multiprocessing package doesn't flush stderr on child exception

Jon Brandvein added the comment: Some more information: When I write to a new file created by open(), all versions flush correctly. However, if I reassign sys.stdout to that file, Python 3.x does not (again, under Windows). I wonder what it is that causes these other files to flush. (Note: I

[issue13812] multiprocessing package doesn't flush stderr on child exception

Jon Brandvein added the comment: I've been looking over this package some more, and in particular, /Lib/multiprocessing/forking.py. There's plenty I don't understand, and I do have questions, if you would be willing to indulge me. I see that both the unix and windows codepaths define an "exit

[issue13812] multiprocessing package doesn't flush stderr on child exception

Antoine Pitrou added the comment: Le dimanche 22 janvier 2012 à 17:58 +, Jon Brandvein a écrit : > Jon Brandvein added the comment: > > On Windows, the problem appears under Python 3.2.2 and 3.1.3, but not > under 2.7.1. On Linux, I have not reproduced the problem on versions > 2.6.3, 2.7.

[issue13812] multiprocessing package doesn't flush stderr on child exception

Jon Brandvein added the comment: On Windows, the problem appears under Python 3.2.2 and 3.1.3, but not under 2.7.1. On Linux, I have not reproduced the problem on versions 2.6.3, 2.7.2, 3.1.1, or 3.2.2. So to summarize: - It seems there should be a stderr flush call on the line I indicated

[issue13812] multiprocessing package doesn't flush stderr on child exception

Antoine Pitrou added the comment: > But I observe that unless I explicitly flush stdout and stderr before > terminating, the output is lost entirely, even if the exit is not > abnormal. This isn't the desired behavior, is it? Indeed that's a bit surprising. Which Python version are you using?

[issue13812] multiprocessing package doesn't flush stderr on child exception

Changes by Terry J. Reedy : -- nosy: +jnoller stage: -> test needed versions: -Python 3.4 ___ Python tracker ___ ___ Python-bugs-lis

[issue13812] multiprocessing package doesn't flush stderr on child exception

Jon Brandvein added the comment: (Er, that should be /Lib/multiprocessing/process.py :: Process._bootstrap of course.) -- ___ Python tracker ___ ___

[issue13812] multiprocessing package doesn't flush stderr on child exception

New submission from Jon Brandvein : When a child process exits due to an exception, a traceback is written, but stderr is not flushed. Thus I see a header like "Process 1:\n", but no traceback. I don't have a development environment or any experience with Mecurial, so I'm afraid there's no pa