Re: BUG #18334: Segfault when running a query with parallel workers

On Fri, May 24, 2024 at 12:45 PM Thomas Munro <thomas.munro@gmail.com> wrote:
> I wondered if the tricky edge case where a segment gets unmapped and
> then then remapped in the same slot could be leading to segment
> confusion.  That does involve a bit of memory order footwork.  What
> CPU architecture is this?  But alas I can't come up with any case
> where that could go wrong even if there is an unknown bug in that
> area, because the no-rebatching, no-rebucketing case doesn't free
> anything until the end when it frees everything (ie it never frees
> something and then allocate, a requirement for slot re-use).

... but if I'm missing something there, it might be a clue visible
from gdb if area->control->freed_segment_counter (the one in shared
memory) and area->freed_segment_counter (the one in this backend) have
different values, if your core captured the segments.