On Thu, Apr 5, 2018 at 11:23 PM, Andres Freund <andres@anarazel.de> wrote:
Hi, On 2018-04-05 22:06:36 +0200, Magnus Hagander wrote: > I have now pushed this latest version with some minor text adjustments and > a catversion bump.
Is there any sort of locking that guarantees that worker processes see an up2date value of DataChecksumsNeedWrite()/ControlFile->data_checksum_version? Afaict there's not. So you can afaict end up with checksums being computed by the worker, but concurrent writes missing them. The window is going to be at most one missed checksum per process (as the unlocking of the page is a barrier) and is probably not easy to hit, but that's dangerous enough.
So just to be clear of the case you're worried about. It's basically:
And at this point, Session #2 has still not seen the "checksums inprogress" flag and continues to write without checksums?
That seems like quite a long time to me -- is that really a problem? I'm guessing you're seeing a shorter path between the two that I can't see right now (I'll blame the late evning...)?
