Re: [HACKERS] Optional message to user when terminating/cancelling backend - Mailing list pgsql-hackers

From Tom Lane
Subject Re: [HACKERS] Optional message to user when terminating/cancelling backend
Date
Msg-id 3915.1535050417@sss.pgh.pa.us
Whole thread Raw
In response to Re: [HACKERS] Optional message to user when terminating/cancelling backend  (Thomas Munro <thomas.munro@enterprisedb.com>)
Responses Re: [HACKERS] Optional message to user when terminating/cancelling backend
Re: [HACKERS] Optional message to user when terminating/cancellingbackend
List pgsql-hackers
Thomas Munro <thomas.munro@enterprisedb.com> writes:
> On Wed, Jul 25, 2018 at 7:27 PM, Daniel Gustafsson <daniel@yesql.se> wrote:
>> Seems the build of the updated patch built and tested Ok.  Still have no idea
>> why the previous one didn’t.

> That problem apparently didn't go away.  cfbot tested it 7 times in
> the past week, and it passed only once on Windows:
> https://ci.appveyor.com/project/postgresql-cfbot/postgresql/build/1.0.9691
> The other times all failed like this:
> https://ci.appveyor.com/project/postgresql-cfbot/postgresql/build/1.0.9833

I think this is just a timing problem: the signal gets sent,
but it might or might not get received before the current statement ends.
It's possible that a signal-sent-to-self can be expected to be received
synchronously on all Unix platforms, but I wouldn't entirely bet on that
(in particular, the POSIX text for kill(2) does NOT guarantee it); and
our Windows signal implementation certainly doesn't guarantee anything
of the sort.

I don't think there's necessarily anything wrong with the code, but
you can't test it with such a simplistic test as this and expect
stable results.  If you feel an urgent need to have a test case,
try building an isolationtester script.

            regards, tom lane


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