On Sat, Oct 27, 2018 at 8:52 PM Andres Freund <and...@anarazel.de> wrote: > On October 27, 2018 3:36:45 PM GMT+01:00, Amit Kapila > <amit.kapil...@gmail.com> wrote: > >On Sat, Oct 27, 2018 at 4:11 PM Andres Freund <and...@anarazel.de> > >wrote: > >> > >> Hi, > >> > >> I just noticed, while working on a patch adding things to PGPROC, > >that > >> the group clearning patches for the proc array and clog reset atomics > >in > >> InitProcess(). > >> > >> I'm not a big fan of that, because it means that it's not safe to > >look > >> at the atomics of backends that aren't currently in use. Is there > >any > >> reason to not instead initialize them in InitProcGlobal() and just > >> assert in InitProcess() that they're 0? > >> > > > >It seems the code written has followed a natural practice i.e PGPROC > >members are initialized in InitProcess and ProcGlobal members (like > >procArrayGroupFirst) are initialized in InitProcGlobal. For your use > >case, can't you look at procArrayGroupFirst? If not, then I think we > >can do what you are saying as I don't see a problem in initializing > >them in InitProcGlobal. > > In my opinion that's an argument for resetting the contents with > pg_atomic_write, but not reinitializing the atomic >
Okay, makes sense. > (which could reset the spinlock inside while somebody else holds it). > This part is not clear to me, how can this happen? I think we only access these variable for active procs which means no-one can hold it till it's reinitialized. > It's not really a problem for me, but I think the code is pretty much wrong > like this... > I think I understand why it is better to write the way you are suggesting, but not clear how the current code can lead to a problem, can you please explain in more detail? -- With Regards, Amit Kapila. EnterpriseDB: http://www.enterprisedb.com
