Обсуждение: locking change help

I am trying to change the lock manager so read locks will not be granted
if there is a write-lock waiting for a lock.  The following patch helps,
but is incomplete.  Can someone figure out the right fix?  I tried
putting this code inside LockResolveConflicts(), but that didn't work
either.

---------------------------------------------------------------------------

*** ./backend/storage/lmgr/lock.c.orig    Fri Jan 23 01:18:01 1998
--- ./backend/storage/lmgr/lock.c    Fri Jan 23 01:18:53 1998
***************
*** 602,607 ****
--- 602,620 ----

      status = LockResolveConflicts(ltable, lock, lockt, myXid);

+         /* ------------------------
+          * If someone with a greater priority is waiting for the lock,
+          * do not continue and share the lock, even if we can.  bjm
+          * ------------------------
+          */
+         int                myprio = ltable->ctl->prio[lockt];
+         PROC_QUEUE        *waitQueue = &(lock->waitProcs);
+         PROC            *topproc = (PROC *) MAKE_PTR(waitQueue->links.prev);
+
+         if (topproc && topproc->prio > myprio)
+             status = STATUS_FOUND;
+     }
+
      if (status == STATUS_OK)
      {
          GrantLock(lock, lockt);

--
Bruce Momjian
maillist@candle.pha.pa.us

Bruce Momjian wrote:
>
> I am trying to change the lock manager so read locks will not be granted
> if there is a write-lock waiting for a lock.  The following patch helps,
> but is incomplete.  Can someone figure out the right fix?  I tried
> putting this code inside LockResolveConflicts(), but that didn't work
> either.

Is this to help writers from starving?

/* m */

>
> Bruce Momjian wrote:
> >
> > I am trying to change the lock manager so read locks will not be granted
> > if there is a write-lock waiting for a lock.  The following patch helps,
> > but is incomplete.  Can someone figure out the right fix?  I tried
> > putting this code inside LockResolveConflicts(), but that didn't work
> > either.
>
> Is this to help writers from starving?

Yes.

--
Bruce Momjian
maillist@candle.pha.pa.us