[PATCH] Fix for Bug #5807

[Sascha Nemecek]

On 08/03/18 13:16, Yuya Nishihara wrote:
> On Wed, 7 Mar 2018 22:48:01 +0100, Sascha Nemecek wrote:
>> Am 2018-03-02 um 05:14 schrieb Yuya Nishihara:
>>> On Thu, 1 Mar 2018 11:06:59 +0100, Sascha Nemecek wrote:
>>>> # HG changeset patch
>>>> # User Sascha Nemecek <nemecek at wienfluss.net>
>>>> # Date 1519831479 -3600
>>>> #      Wed Feb 28 16:24:39 2018 +0100
>>>> # Node ID 42ddf4ee4f91d76f19ca0c3efc4c8e4c1c6fa96c
>>>> # Parent  1bd132a021dd00f96604e33a8fb5306d37e56007
>>>> Don't close 'fp' (= 'ui.fout') stream to prevent 'ValueError: I/O
>>>> operation on closed file' (Bug #5807).
>>>>
>>>> Regression of changeset 30261:6bed17ba00a1
>>>> (https://www.mercurial-scm.org/repo/hg/rev/6bed17ba00a1)
>>>>
>>>> diff -r 1bd132a021dd -r 42ddf4ee4f91 hgext/convert/subversion.py
>>>> --- a/hgext/convert/subversion.py	Wed Feb 21 14:36:42 2018 +0530
>>>> +++ b/hgext/convert/subversion.py	Wed Feb 28 16:24:39 2018 +0100
>>>> @@ -149,7 +149,7 @@
>>>>            pickle.dump(str(inst), fp, protocol)
>>>>        else:
>>>>            pickle.dump(None, fp, protocol)
>>>> -    fp.close()
>>>> +    fp.flush()
>>>>        # With large history, cleanup process goes crazy and suddenly
>>>>        # consumes *huge* amount of memory. The output file being closed,
>>>>        # there is no need for clean termination.
>>>
>>> I don't think fp.close() was the source of the problem. Here the process
>>> _exit()s so no cleanup would be run.
>>
>> Of course, the problem might lie deeper. Empirically tested, the
>> fp.close() triggered the reported error output. From my observation, the
>> fp.close() affected stdout of the convert function and also pdb.
>> Therefore I came to the conclusion that the fp.close() / ui.fout.close()
>> was the culprit.
> 
> If this patch magically fixes the issue, that's fine. It's also harmless
> to do fflush() instead of fclose() here. I'm just saying that the process
> exits immediately after the fp.close() with no cleanup, so I have no idea
> why that matters.
> 
>    -fp.close()
>    +fp.flush()
>     os._exit(0)

My guess/interpretation is, that this happens in a child process. When 
closing ui.fout, the parent and all other process run into closed doors.


Best regards,
Sascha