Re: SIGSEGV from START_REPLICATION 0/XXXXXXX in XLogSendPhysical () at walsender.c:2762

At Thu, 28 May 2020 09:07:04 +0300, Vladimir Sitnikov <sitnikov(dot)vladimir(at)gmail(dot)com> wrote in
> Pgjdbc test suite identified a SIGSEGV in the recent HEAD builds of
> PostgreSQL, Ubuntu 14.04.5 LTS
>
> Here's a call stack:
> https://travis-ci.org/github/pgjdbc/pgjdbc/jobs/691794110#L7484
> The crash is consistent, and it reproduces 100% of the cases so far.
>
> The CI history shows that HEAD was good at 11 May 13:27 UTC, and it became
> bad by 19 May 14:00 UTC,
> so the regression was introduced somewhere in-between.
>
> Does that ring any bells?

Thanks for the report. It is surely a bug since the server crashes,
on the other hand Pgjdbc seems doing bad, too.

It seems to me that that crash means Pgjdbc is initiating a logical
replication connection to start physical replication.

> In case you wonder:
>
> Program terminated with signal SIGSEGV, Segmentation fault.
> #0 XLogSendPhysical () at walsender.c:2762
> 2762 if (!WALRead(xlogreader,
> (gdb) #0 XLogSendPhysical () at walsender.c:2762
> SendRqstPtr = 133473640
> startptr = 133473240
> endptr = 133473640
> nbytes = 400
> segno = 1
> errinfo = {wre_errno = 988942240, wre_off = 2, wre_req = -1,
> wre_read = -1, wre_seg = {ws_file = 4714224,
> ws_segno = 140729887364688, ws_tli = 0}}
> __func__ = "XLogSendPhysical"

I see the probably the same symptom by the following steps with the
current HEAD.

psql 'host=/tmp replication=database'
=# START_REPLICATION 0/1;
<serer crashes>

Physical replication is not assumed to be started on a logical
replication connection. The attached would fix that. The patch adds
two tests. One for this case and another for the reverse.

regards.

--
Kyotaro Horiguchi
NTT Open Source Software Center