Re: Dead code or buggy code?

So I'm just going to make the code defensive and assume NULL is possible
when if maybe it isn't.

In case it's not clear, this is one of the thing's Xi Wang's took picked
up. There not to many but it turns out they are indeed not all in the adt
code so I might wait until after the commit fest to commit it to avoid
causing bit churn.

--
greg
On 19 Sep 2013 12:52, "Robert Haas" <robertmhaas(at)gmail(dot)com> wrote:

> On Wed, Sep 18, 2013 at 6:20 PM, Greg Stark <stark(at)mit(dot)edu> wrote:
> > The following code is in the ProcSleep at proc.c:1138.
> > GetBlockingAutoVacuumPgproc() should presumably always return a vacuum
> > pgproc entry since the deadlock state says it's blocked by autovacuum.
> > But I'm not really familiar enough with this codepath to know whether
> > there's not a race condition here where it can sometimes return null.
> > The following code checks autovac != NULL but the PGXACT initializer
> > would have seg faulted if it returned NULL if that's possible.
> >
> > if (deadlock_state == DS_BLOCKED_BY_AUTOVACUUM &&
> > allow_autovacuum_cancel)
> > {
> > PGPROC *autovac = GetBlockingAutoVacuumPgproc();
> > PGXACT *autovac_pgxact =
> > &ProcGlobal->allPgXact[autovac->pgprocno];
> >
> > LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
> >
> > /*
> > * Only do it if the worker is not working to protect
> against Xid
> > * wraparound.
> > */
> > if ((autovac != NULL) &&
> > (autovac_pgxact->vacuumFlags & PROC_IS_AUTOVACUUM) &&
> > !(autovac_pgxact->vacuumFlags &
> PROC_VACUUM_FOR_WRAPAROUND))
> > {
>
> Hmm, yeah. I remember noticing this some time ago but never got
> around to fixing it. +1 for rearranging things there somehow.
>
> --
> Robert Haas
> EnterpriseDB: http://www.enterprisedb.com
> The Enterprise PostgreSQL Company
>