On 5/10/19 3:35 PM, Tom Lane wrote: > Andres Freund <and...@anarazel.de> writes: >> On 2019-05-10 11:38:57 -0400, Tom Lane wrote: >>> I am wondering if, somehow, the stack depth limit seen by the postmaster >>> sometimes doesn't apply to its children. That would be pretty wacko >>> kernel behavior, especially if it's only intermittently true. >>> But we're running out of other explanations. >> I wonder if this is a SIGSEGV that actually signals an OOM >> situation. Linux, if it can't actually extend the stack on-demand due to >> OOM, sends a SIGSEGV. The signal has that information, but >> unfortunately the buildfarm code doesn't print it. p $_siginfo would >> show us some of that... >> Mark, how tight is the memory on that machine? Does dmesg have any other >> information (often segfaults are logged by the kernel with the code >> IIRC). > It does sort of smell like a resource exhaustion problem, especially > if all these buildfarm animals are VMs running on the same underlying > platform. But why would that manifest as "you can't have a measly two > megabytes of stack" and not as any other sort of OOM symptom? > > Mark, if you don't mind modding your local copies of the buildfarm > script, I think what Andres is asking for is a pretty trivial addition > in PGBuild/Utils.pm's sub get_stack_trace: > > my $cmdfile = "./gdbcmd"; > my $handle; > open($handle, '>', $cmdfile) || die "opening $cmdfile: $!"; > print $handle "bt\n"; > + print $handle "p $_siginfo\n"; > close($handle); > >
I think we'll need to write that as: print $handle 'p $_siginfo',"\n"; As you have it written perl will try to interpolate a variable called $_siginfo. cheers andrew
