Re: Recent SIGSEGV failures in buildfarm HEAD

Stefan Kaltenbrunner <stefan(at)kaltenbrunner(dot)cc> writes:
> Tom Lane wrote:
>> Stefan Kaltenbrunner <stefan(at)kaltenbrunner(dot)cc> writes:
>>> ... Maybe something is causing a dramatic
>>> increase in memory usage that is causing the random failures (in impalas
>>> case the OOM-killer actually decides to terminate the postmaster) ?
>>
>> No, most all the failures I've looked at are sig11 not sig9.

> hmm - still weird and I would not actually consider impala a resource
> starved box (especially when compared to other buildfarm-members) so
> there seems to be something strange going on.

Actually ... one way that a "memory overconsumption" bug could manifest
as sig11 would be if it's a runaway-recursion issue: usually you get sig11
when the machine's stack size limit is exceeded. This doesn't put us
any closer to localizing the problem, but at least it's a guess about
the cause?

I wonder whether there's any way to get the buildfarm script to report a
stack trace automatically if it finds a core file left behind in the
$PGDATA directory after running the tests. Would something like this
be adequately portable?

if [ -f $PGDATA/core* ]
then
echo bt | gdb $installdir/bin/postgres $PGDATA/core*
fi

Obviously it'd fail if no gdb available, but that seems pretty harmless.
The other thing that we'd likely need is an explicit "ulimit -c
unlimited" for machines where core dumps are off by default.

regards, tom lane