Index: dbfile.scm
==================================================================
--- dbfile.scm
+++ dbfile.scm
@@ -82,11 +82,12 @@
   (stmt-cache  (make-hash-table))
   (read-only   #f)
   (birth-sec   (current-seconds)))
 
 (define *dbstruct-dbs* #f)
-(define *db-access-mutex* (make-mutex))
+(define *db-open-mutex* (make-mutex))
+(define *db-access-mutex* (make-mutex)) ;; used in common.scm
 (define *no-sync-db*   #f)
 (define *db-sync-in-progress* #f)
 (define *db-with-db-mutex*    (make-mutex))
 (define *max-api-process-requests* 0)
 (define *api-process-request-count* 0)
@@ -275,10 +276,11 @@
 (define (dbfile:open-db dbstruct run-id init-proc)
   (if (> *dbfile:num-handles-in-use* 10)
       (let* ((wait-delay (- *dbfile:num-handles-in-use* 9)))
 	(dbfile:print-err "INFO: over ten dbfile handle threads in use ("*dbfile:num-handles-in-use*") delaying "wait-delay" second")
 	(thread-sleep! wait-delay)))
+  
   (let* ((subdb (dbfile:get-subdb dbstruct run-id)))
     (if (not subdb) ;; not yet defined
 	(begin
 	  (dbfile:init-subdb dbstruct run-id init-proc)
 	  (dbfile:open-db dbstruct run-id init-proc))
@@ -718,11 +720,11 @@
   (let* (;; the subdb is needed to access the mtdbdat
 	 (subdb     (or (dbfile:get-subdb dbstruct run-id)
 			(dbfile:init-subdb dbstruct run-id dbinit)))
          (tmpdbfile (dbr:subdb-tmpdbfile subdb))
 	 (mtdb      (dbr:subdb-mtdbdat subdb))
-         (tmpdb     (dbfile:open-db dbstruct run-id dbinit)) ;; sqlite3-db tmpdbfile #f))
+         (tmpdb     (db:open-db dbstruct run-id dbinit)) ;; sqlite3-db tmpdbfile #f))
 	 (start-t   (current-seconds)))
     (mutex-lock! *db-multi-sync-mutex*)
     (let ((update_info (cons "last_update" (if force-sync 0 *db-last-sync*) )))
       (mutex-unlock! *db-multi-sync-mutex*)
       (db:sync-tables (db:sync-all-tables-list dbstruct keys) update_info tmpdb mtdb))
@@ -1147,12 +1149,14 @@
 ;;======================================================================
 
 ;; call with dbinit=db:initialize-main-db
 ;;
 (define (db:open-db dbstruct run-id dbinit)
+  (mutex-lock! *db-open-mutex*)
   (let* ((dbdat (dbfile:open-db dbstruct run-id dbinit)))
     (set! *db-write-access* (not (dbr:dbdat-read-only dbdat)))
+    (mutex-unlock! *db-open-mutex*)
     dbdat))
 
 (define dbfile:db-init-proc (make-parameter #f))
 
 ;; (db:with-db dbstruct run-id sqlite3:exec "select blah fgrom blaz;")