diff -ru postgresql-head/doc/src/sgml/func.sgml postgresql/doc/src/sgml/func.sgml
--- postgresql-head/doc/src/sgml/func.sgml	2012-04-03 10:44:43.979702643 +0200
+++ postgresql/doc/src/sgml/func.sgml	2012-04-03 11:24:41.427701474 +0200
@@ -14467,6 +14467,9 @@
     <primary>pg_stop_backup</primary>
    </indexterm>
    <indexterm>
+    <primary>pg_is_in_backup</primary>
+   </indexterm>
+   <indexterm>
     <primary>pg_switch_xlog</primary>
    </indexterm>
    <indexterm>
@@ -14532,6 +14535,13 @@
       </row>
       <row>
        <entry>
+        <literal><function>pg_is_in_backup()</function></literal>
+        </entry>
+       <entry><type>bool</type></entry>
+       <entry>True if an on-line exclusive backup is still in progress.</entry>
+      </row>
+      <row>
+       <entry>
         <literal><function>pg_switch_xlog()</function></literal>
         </entry>
        <entry><type>text</type></entry>
diff -ru postgresql-head/src/backend/access/transam/xlogfuncs.c postgresql/src/backend/access/transam/xlogfuncs.c
--- postgresql-head/src/backend/access/transam/xlogfuncs.c	2012-04-03 10:44:44.227702645 +0200
+++ postgresql/src/backend/access/transam/xlogfuncs.c	2012-04-03 11:24:41.427701474 +0200
@@ -563,3 +563,12 @@
 
 	PG_RETURN_NUMERIC(result);
 }
+
+/*
+ * Returns bool with current on-line backup mode, a global state.
+ */
+Datum
+pg_is_in_backup(PG_FUNCTION_ARGS)
+{
+       PG_RETURN_BOOL(BackupInProgress());
+}
diff -ru postgresql-head/src/include/access/xlog_internal.h postgresql/src/include/access/xlog_internal.h
--- postgresql-head/src/include/access/xlog_internal.h	2012-04-03 10:44:45.051702642 +0200
+++ postgresql/src/include/access/xlog_internal.h	2012-04-03 11:24:41.427701474 +0200
@@ -282,5 +282,6 @@
 extern Datum pg_xlog_replay_resume(PG_FUNCTION_ARGS);
 extern Datum pg_is_xlog_replay_paused(PG_FUNCTION_ARGS);
 extern Datum pg_xlog_location_diff(PG_FUNCTION_ARGS);
+extern Datum pg_is_in_backup(PG_FUNCTION_ARGS);
 
 #endif   /* XLOG_INTERNAL_H */
diff -ru postgresql-head/src/include/catalog/pg_proc.h postgresql/src/include/catalog/pg_proc.h
--- postgresql-head/src/include/catalog/pg_proc.h	2012-04-03 10:44:45.051702642 +0200
+++ postgresql/src/include/catalog/pg_proc.h	2012-04-03 11:24:41.427701474 +0200
@@ -2924,6 +2924,8 @@
 DESCR("prepare for taking an online backup");
 DATA(insert OID = 2173 ( pg_stop_backup			PGNSP PGUID 12 1 0 0 0 f f f f t f v 0 0 25 "" _null_ _null_ _null_ _null_ pg_stop_backup _null_ _null_ _null_ ));
 DESCR("finish taking an online backup");
+DATA(insert OID = 3882 ( pg_is_in_backup		PGNSP PGUID 12 1 0 0 0 f f f f t f v 0 0 16 "" _null_ _null_ _null_ _null_ pg_is_in_backup _null_ _null_ _null_ ));
+DESCR("true if server is in online backup");
 DATA(insert OID = 2848 ( pg_switch_xlog			PGNSP PGUID 12 1 0 0 0 f f f f t f v 0 0 25 "" _null_ _null_ _null_ _null_ pg_switch_xlog _null_ _null_ _null_ ));
 DESCR("switch to new xlog file");
 DATA(insert OID = 3098 ( pg_create_restore_point	PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 25 "25" _null_ _null_ _null_ _null_ pg_create_restore_point _null_ _null_ _null_ ));