3 files changed, 55 insertions, 5 deletions
diff --git a/src/include/access/nbtree.h b/src/include/access/nbtree.h
index 2bcf8ab38f4..fc8b30b2ea9 100644
--- a/src/include/access/nbtree.h
+++ b/src/include/access/nbtree.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/access/nbtree.h,v 1.116 2008/01/01 19:45:56 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/access/nbtree.h,v 1.116.2.1 2008/04/16 23:59:51 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -574,6 +574,7 @@ extern void _bt_killitems(IndexScanDesc scan, bool haveLock);
 extern BTCycleId _bt_vacuum_cycleid(Relation rel);
 extern BTCycleId _bt_start_vacuum(Relation rel);
 extern void _bt_end_vacuum(Relation rel);
+extern void _bt_end_vacuum_callback(int code, Datum arg);
 extern Size BTreeShmemSize(void);
 extern void BTreeShmemInit(void);
 
diff --git a/src/include/storage/ipc.h b/src/include/storage/ipc.h
index eb89f9a7dae..8f4bbcb90eb 100644
--- a/src/include/storage/ipc.h
+++ b/src/include/storage/ipc.h
@@ -11,21 +11,63 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/storage/ipc.h,v 1.74 2008/01/01 19:45:59 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/storage/ipc.h,v 1.74.2.1 2008/04/16 23:59:51 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
 #ifndef IPC_H
 #define IPC_H
 
+typedef void (*pg_on_exit_callback) (int code, Datum arg);
+
+/*----------
+ * API for handling cleanup that must occur during either ereport(ERROR)
+ * or ereport(FATAL) exits from a block of code.  (Typical examples are
+ * undoing transient changes to shared-memory state.)
+ *
+ *		PG_ENSURE_ERROR_CLEANUP(cleanup_function, arg);
+ *		{
+ *			... code that might throw ereport(ERROR) or ereport(FATAL) ...
+ *		}
+ *		PG_END_ENSURE_ERROR_CLEANUP(cleanup_function, arg);
+ *
+ * where the cleanup code is in a function declared per pg_on_exit_callback.
+ * The Datum value "arg" can carry any information the cleanup function
+ * needs.
+ *
+ * This construct ensures that cleanup_function() will be called during
+ * either ERROR or FATAL exits.  It will not be called on successful
+ * exit from the controlled code.  (If you want it to happen then too,
+ * call the function yourself from just after the construct.)
+ *
+ * Note: the macro arguments are multiply evaluated, so avoid side-effects.
+ *----------
+ */
+#define PG_ENSURE_ERROR_CLEANUP(cleanup_function, arg)  \
+	do { \
+		on_shmem_exit(cleanup_function, arg); \
+		PG_TRY()
+
+#define PG_END_ENSURE_ERROR_CLEANUP(cleanup_function, arg)  \
+		cancel_shmem_exit(cleanup_function, arg); \
+		PG_CATCH(); \
+		{ \
+			cancel_shmem_exit(cleanup_function, arg); \
+			cleanup_function (0, arg); \
+			PG_RE_THROW(); \
+		} \
+		PG_END_TRY(); \
+	} while (0)
+
 
 /* ipc.c */
 extern bool proc_exit_inprogress;
 
 extern void proc_exit(int code);
 extern void shmem_exit(int code);
-extern void on_proc_exit(void (*function) (int code, Datum arg), Datum arg);
-extern void on_shmem_exit(void (*function) (int code, Datum arg), Datum arg);
+extern void on_proc_exit(pg_on_exit_callback function, Datum arg);
+extern void on_shmem_exit(pg_on_exit_callback function, Datum arg);
+extern void cancel_shmem_exit(pg_on_exit_callback function, Datum arg);
 extern void on_exit_reset(void);
 
 /* ipci.c */
diff --git a/src/include/utils/elog.h b/src/include/utils/elog.h
index 57ca1533928..04843eecd30 100644
--- a/src/include/utils/elog.h
+++ b/src/include/utils/elog.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/utils/elog.h,v 1.90 2008/01/01 19:45:59 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/utils/elog.h,v 1.90.2.1 2008/04/16 23:59:51 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -198,6 +198,13 @@ extern PGDLLIMPORT ErrorContextCallback *error_context_stack;
  * of levels this will work for.  It's best to keep the error recovery
  * section simple enough that it can't generate any new errors, at least
  * not before popping the error stack.
+ *
+ * Note: an ereport(FATAL) will not be caught by this construct; control will
+ * exit straight through proc_exit().  Therefore, do NOT put any cleanup
+ * of non-process-local resources into the error recovery section, at least
+ * not without taking thought for what will happen during ereport(FATAL).
+ * The PG_ENSURE_ERROR_CLEANUP macros provided by storage/ipc.h may be
+ * helpful in such cases.
  *----------
  */
 #define PG_TRY()  \