Modify interactions between sinval.c and sinvaladt.c. The code that actually

deals with the queue, including locking etc, is all in sinvaladt.c.  This means
that the struct definition of the queue, and the queue pointer, are now
internal "implementation details" inside sinvaladt.c.

Per my proposal dated 25-Jun-2007 and followup discussion.

Author: alvherre

src/backend/storage/ipc/ipci.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/ipc/ipci.c,v 1.94 2008/01/01 19:45:51 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/ipc/ipci.c,v 1.95 2008/03/16 19:47:33 alvherre Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -30,7 +30,7 @@
 #include "storage/pg_shmem.h"
 #include "storage/pmsignal.h"
 #include "storage/procarray.h"
-#include "storage/sinval.h"
+#include "storage/sinvaladt.h"
 #include "storage/spin.h"
 
 

src/backend/storage/ipc/sinval.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/ipc/sinval.c,v 1.83 2008/01/01 19:45:51 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/ipc/sinval.c,v 1.84 2008/03/16 19:47:33 alvherre Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -48,38 +48,6 @@ static volatile int catchupInterruptOccurred = 0;
 static void ProcessCatchupEvent(void);
 
 
-/****************************************************************************/
-/*	CreateSharedInvalidationState()		 Initialize SI buffer				*/
-/*																			*/
-/*	should be called only by the POSTMASTER									*/
-/****************************************************************************/
-void
-CreateSharedInvalidationState(void)
-{
-	/* SInvalLock must be initialized already, during LWLock init */
-	SIBufferInit();
-}
-
-/*
- * InitBackendSharedInvalidationState
- *		Initialize new backend's state info in buffer segment.
- */
-void
-InitBackendSharedInvalidationState(void)
-{
-	int			flag;
-
-	LWLockAcquire(SInvalLock, LW_EXCLUSIVE);
-	flag = SIBackendInit(shmInvalBuffer);
-	LWLockRelease(SInvalLock);
-	if (flag < 0)				/* unexpected problem */
-		elog(FATAL, "shared cache invalidation initialization failed");
-	if (flag == 0)				/* expected problem: MaxBackends exceeded */
-		ereport(FATAL,
-				(errcode(ERRCODE_TOO_MANY_CONNECTIONS),
-				 errmsg("sorry, too many clients already")));
-}
-
 /*
  * SendSharedInvalidMessage
  *	Add a shared-cache-invalidation message to the global SI message queue.
@@ -89,9 +57,7 @@ SendSharedInvalidMessage(SharedInvalidationMessage *msg)
 {
 	bool		insertOK;
 
-	LWLockAcquire(SInvalLock, LW_EXCLUSIVE);
-	insertOK = SIInsertDataEntry(shmInvalBuffer, msg);
-	LWLockRelease(SInvalLock);
+	insertOK = SIInsertDataEntry(msg);
 	if (!insertOK)
 		elog(DEBUG4, "SI buffer overflow");
 }
@@ -123,19 +89,7 @@ ReceiveSharedInvalidMessages(
 		 */
 		catchupInterruptOccurred = 0;
 
-		/*
-		 * We can run SIGetDataEntry in parallel with other backends running
-		 * SIGetDataEntry for themselves, since each instance will modify only
-		 * fields of its own backend's ProcState, and no instance will look at
-		 * fields of other backends' ProcStates.  We express this by grabbing
-		 * SInvalLock in shared mode.  Note that this is not exactly the
-		 * normal (read-only) interpretation of a shared lock! Look closely at
-		 * the interactions before allowing SInvalLock to be grabbed in shared
-		 * mode for any other reason!
-		 */
-		LWLockAcquire(SInvalLock, LW_SHARED);
-		getResult = SIGetDataEntry(shmInvalBuffer, MyBackendId, &data);
-		LWLockRelease(SInvalLock);
+		getResult = SIGetDataEntry(MyBackendId, &data);
 
 		if (getResult == 0)
 			break;				/* nothing more to do */
@@ -155,11 +109,7 @@ ReceiveSharedInvalidMessages(
 
 	/* If we got any messages, try to release dead messages */
 	if (gotMessage)
-	{
-		LWLockAcquire(SInvalLock, LW_EXCLUSIVE);
-		SIDelExpiredDataEntries(shmInvalBuffer);
-		LWLockRelease(SInvalLock);
-	}
+		SIDelExpiredDataEntries(false);
 }