Andres Freund wrote:
> On 2016-03-28 15:46:43 +0300, Alexander Korotkov wrote:

> > @@ -932,8 +936,13 @@ ReadBuffer_common(SMgrRelation smgr, cha
> >  
> >     if (isLocalBuf)
> >     {
> > -           /* Only need to adjust flags */
> > -           bufHdr->flags |= BM_VALID;
> > +           /*
> > +            * Only need to adjust flags.  Since it's local buffer, there 
> > is no
> > +            * concurrency.  We assume read/write pair to be cheaper than 
> > atomic OR.
> > +            */
> > +           uint32 state = pg_atomic_read_u32(&bufHdr->state);
> > +           state |= BM_VALID;
> > +           pg_atomic_write_u32(&bufHdr->state, state);
> 
> I'm not a fan of repeating that comment in multiple places. Hm.

Perhaps a set of macros should be offered that do "read, set some flag,
write".  Then the comments can be attached to the macro instead of to
each callsite.

-- 
Álvaro Herrera                http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services


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