Re: Online enabling of checksums

On 2018-04-06 19:40:59 +0200, Tomas Vondra wrote:
> In any case, I wouldn't call LockBufHdr/UnlockBufHdr a "side channel"
> interlock. It's a pretty direct and intentional interlock, I think.

I mean it's a side-channel as far as DataChecksumsNeedWrite() is
concerned. You're banking on all callers using a barrier implying
operation around it.


> Sure. But what would that be? I can't think of anything. A process that
> modifies a buffer (or any other piece of shared state) without holding
> some sort of lock seems broken by default.

You can quite possibly already *hold* a lock if it's not an exclusive
one.

Greetings,

Andres Freund