On 2020-Aug-31, Andres Freund wrote: > Hi, > > On August 31, 2020 11:21:56 AM PDT, Alvaro Herrera <alvhe...@2ndquadrant.com> > wrote:
> >At first I wanted to make the new LWLock cover only LogwrtResult > >proper, > >and leave LogwrtRqst alone. However on doing it, it seemed that that > >might change the locking protocol in a nontrivial way. So I decided to > >make it cover both and call it a day. We did verify that the patch > >solves the reported problem, at any rate. > > Wouldn't the better fix here be to allow reading of individual members > without a lock? E.g. by wrapping each in a 64bit atomic. Heh, Simon said the same. It's not clear to me due to the lack of general availability of 64-bit atomics. If they are spinlock-protected when emulated, I think that would make the problem worse. IIRC Thomas wanted to start relying on atomic 64-bit vars in some patch, but I don't remember what it was. -- Álvaro Herrera https://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
