Revert removal of trace_userlocks, because userlocks aren't gone.

This reverts commit 0180bd61.
contrib/userlock is gone, but user-level locking still exists,
and is exposed via the pg_advisory* family of functions.

doc/src/sgml/config.sgml

@@ -6217,6 +6217,28 @@ LOG:  CleanUpLock: deleting: lock(0xb7acd844) id(24688,24696,0,0,0,1)
       </listitem>
      </varlistentry>
 
+     <varlistentry>
+      <term><varname>trace_userlocks</varname> (<type>boolean</type>)</term>
+      <indexterm>
+       <primary><varname>trace_userlocks</> configuration parameter</primary>
+      </indexterm>
+      <listitem>
+       <para>
+        If on, emit information about user lock usage.  Output is the same
+        as for <symbol>trace_locks</symbol>, only for user locks.
+       </para>
+       <para>
+        User locks were removed as of PostgreSQL version 8.2.  This option
+        currently has no effect.
+       </para>
+       <para>
+        This parameter is only available if the <symbol>LOCK_DEBUG</symbol>
+        macro was defined when <productname>PostgreSQL</productname> was
+        compiled.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry>
       <term><varname>trace_lock_oidmin</varname> (<type>integer</type>)</term>
       <indexterm>

src/backend/storage/lmgr/lock.c

@@ -213,7 +213,12 @@ static const LockMethodData user_lockmethod = {
 	AccessExclusiveLock,		/* highest valid lock mode number */
 	true,
 	LockConflicts,
-	lock_mode_names
+	lock_mode_names,
+#ifdef LOCK_DEBUG
+	&Trace_userlocks
+#else
+	&Dummy_trace
+#endif
 };
 
 /*
@@ -271,6 +276,7 @@ static ResourceOwner awaitedOwner;
 
 int			Trace_lock_oidmin = FirstNormalObjectId;
 bool		Trace_locks = false;
+bool		Trace_userlocks = false;
 int			Trace_lock_table = 0;
 bool		Debug_deadlocks = false;
 

src/backend/utils/misc/check_guc

@@ -20,7 +20,7 @@ INTENTIONALLY_NOT_INCLUDED="autocommit debug_deadlocks \
 is_superuser lc_collate lc_ctype lc_messages lc_monetary lc_numeric lc_time \
 pre_auth_delay role seed server_encoding server_version server_version_int \
 session_authorization trace_lock_oidmin trace_lock_table trace_locks trace_lwlocks \
-trace_notify transaction_isolation transaction_read_only \
+trace_notify trace_userlocks transaction_isolation transaction_read_only \
 zero_damaged_pages"
 
 ### What options are listed in postgresql.conf.sample, but don't appear

src/backend/utils/misc/guc.c

@@ -1060,6 +1060,16 @@ static struct config_bool ConfigureNamesBool[] =
 		false,
 		NULL, NULL, NULL
 	},
+	{
+		{"trace_userlocks", PGC_SUSET, DEVELOPER_OPTIONS,
+			gettext_noop("No description available."),
+			NULL,
+			GUC_NOT_IN_SAMPLE
+		},
+		&Trace_userlocks,
+		false,
+		NULL, NULL, NULL
+	},
 	{
 		{"trace_lwlocks", PGC_SUSET, DEVELOPER_OPTIONS,
 			gettext_noop("No description available."),

src/include/storage/lock.h

@@ -34,6 +34,7 @@ extern int	max_locks_per_xact;
 #ifdef LOCK_DEBUG
 extern int	Trace_lock_oidmin;
 extern bool Trace_locks;
+extern bool Trace_userlocks;
 extern int	Trace_lock_table;
 extern bool Debug_deadlocks;
 #endif   /* LOCK_DEBUG */