Re: Reproducible "Bus error" in 9.2.3 during database dump restoration (Ubuntu Server 12.04 LTS)

On 03/11/2013 09:20 PM, Dmitry Koterov wrote:
> x86_64, PostgreSQL 9.2. is run within an OpenVZ container and
> generates SIGBUS.
> PostgreSQL 9.1 has no such problem.
>
> (OpenVZ is a linux kernel-level virtualization which adds namespaces
> for processes, networking, quotas etc. It works not like e.g. Xen or
> VMWare, because all containers share the same kernel.)
Related to SHM vs mmapped files? Seems unlikely, but I guess it could
affect low-enough level work like kernel TLB usage.

At what point in Pg's execution does the SIGBUS occur? Is it always at
the same place or few places in the code? It would be helpful if you
could enable core files writing and get backtraces from core files or
(since it's reproducible) by attaching a debugger directly to a Pg
backend. See
http://wiki.postgresql.org/wiki/Getting_a_stack_trace_of_a_running_PostgreSQL_backend_on_Linux/BSD

If you restore just the first half of the table or just the last half
does the crash still happen? If it still happens in one part but not in
another, can you do a binary search* to isolate the smallest chunk of
the input file that still reliably causes the crash?

* (ie: split the file roughly in half at a record boundary and test each
half. Discard the half that doesn't crash, keep the half that crashes.
Repeat the process using the kept half as input until you find the
smallest chunk that still crashes, or get down to a single record that
causes the problem.)

Does the same data cause a crash when restored in another VM on the same
OpenVZ container? What about when restored to another machine with the
same OS and Pg version outside OpenVZ?

--
Craig Ringer http://www.2ndQuadrant.com/
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