On Fri, Jun 06, 2025 at 03:37:45PM -0400, Andres Freund wrote:
> On 2025-06-06 15:21:13 -0400, Tom Lane wrote:
> > So it's our code that is busted. No doubt, what is happening is
> > that process A is fetching two fields, modifying one of them,
> > and storing the word back (with the observed value of the other
> > field) concurrently with some other process trying to update
> > the other field. So the other process's update is lost.
>
> There shouldn't be any concurrent accesses here, so I don't really see
> how the above would explain the problem (the IO can only ever be
> modified by one backend, initially the "owning backend", then, when
> submitted, by the IO worker, and then again by the backend).
No concurrent accesses, not from threads anyways, but not even from
kernel subsystems nor from signal handlers?
