From a243a208bacaeda4d9d8cd3451082b91cdb59e4f Mon Sep 17 00:00:00 2001
From: hvlad <hvlad@users.sourceforge.net>
Date: Mon, 26 Jul 2010 13:31:43 +0000
Subject: [PATCH] Backport fix for bug CORE-3016 : On disconnect it is possible
 to see "Fatal lock manager error: invalid lock id (0), errno: 0" in
 firebird.log

---
 src/jrd/cch.cpp | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/jrd/cch.cpp b/src/jrd/cch.cpp
index 1c7e581d5a..bba18ba44f 100644
--- a/src/jrd/cch.cpp
+++ b/src/jrd/cch.cpp
@@ -330,6 +330,9 @@ int CCH_down_grade_dbb(void* ast_object)
 		return 0;
 	}
 
+	if (dbb->dbb_flags & DBB_not_in_use)
+		return 0;
+
 /* Since this routine will be called asynchronously, we must establish
    a thread context. */
 	thread_db thd_context, *tdbb;