Code review for superuser_reserved_connections patch. Don't try to do

database access outside a transaction; revert bogus performance improvement
in SIBackendInit(); improve comments; add documentation (this part courtesy
Neil Conway).

2 files changed, 19 insertions, 18 deletions

diff --git a/src/backend/storage/ipc/sinval.c b/src/backend/storage/ipc/sinval.c
index 87f7a292452..239c3bc8d30 100644
--- a/src/backend/storage/ipc/sinval.c
+++ b/src/backend/storage/ipc/sinval.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/storage/ipc/sinval.c,v 1.52 2002/09/04 20:31:25 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/storage/ipc/sinval.c,v 1.53 2002/11/21 06:36:08 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -542,12 +542,11 @@ BackendIdGetProc(BackendId procId)
 /*
  * CountEmptyBackendSlots - count empty slots in backend process table
  *
- * Doesn't count since the procState array could be large and we've already
- * allowed for that by running a freeBackends counter in the SI segment.
- * Unlike CountActiveBackends() we do not need to interrogate the
- * backends to determine the free slot count.
- * Goes for a lock despite being a trival look up in case other backends
- * are busy starting or exiting since there is scope for confusion.
+ * We don't actually need to count, since sinvaladt.c maintains a
+ * freeBackends counter in the SI segment.
+ *
+ * Acquiring the lock here is almost certainly overkill, but just in
+ * case fetching an int is not atomic on your machine ...
  */
 int
 CountEmptyBackendSlots(void)
diff --git a/src/backend/storage/ipc/sinvaladt.c b/src/backend/storage/ipc/sinvaladt.c
index b4ab1689f94..6850fa8cf52 100644
--- a/src/backend/storage/ipc/sinvaladt.c
+++ b/src/backend/storage/ipc/sinvaladt.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/storage/ipc/sinvaladt.c,v 1.48 2002/08/29 21:02:12 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/storage/ipc/sinvaladt.c,v 1.49 2002/11/21 06:36:08 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -92,13 +92,6 @@ SIBackendInit(SISeg *segP)
 	int			index;
 	ProcState  *stateP = NULL;
 
-	if (segP->freeBackends == 0)
-	{
-		/* out of procState slots */
-		MyBackendId = InvalidBackendId;
-		return 0;
-	}
-
 	/* Look for a free entry in the procState array */
 	for (index = 0; index < segP->lastBackend; index++)
 	{
@@ -111,9 +104,18 @@ SIBackendInit(SISeg *segP)
 
 	if (stateP == NULL)
 	{
-		stateP = &segP->procState[segP->lastBackend];
-		Assert(stateP->nextMsgNum < 0);
-		segP->lastBackend++;
+		if (segP->lastBackend < segP->maxBackends)
+		{
+			stateP = &segP->procState[segP->lastBackend];
+			Assert(stateP->nextMsgNum < 0);
+			segP->lastBackend++;
+		}
+		else
+		{
+			/* out of procState slots */
+			MyBackendId = InvalidBackendId;
+			return 0;
+		}
 	}
 
 	MyBackendId = (stateP - &segP->procState[0]) + 1;