--- loncom/LONCAPA.pm	2006/06/26 21:19:36	1.8
+++ loncom/LONCAPA.pm	2006/06/27 15:21:28	1.10
@@ -1,7 +1,7 @@
 # The LearningOnline Network
 # Base routines
 #
-# $Id: LONCAPA.pm,v 1.8 2006/06/26 21:19:36 foxr Exp $
+# $Id: LONCAPA.pm,v 1.10 2006/06/27 15:21:28 albertel Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -228,9 +228,28 @@ sub _do_hash_untie {
 
 {
     my $sym;
+    my @pushed_syms;
+    sub push_locking_hash_tie {
+	if (!defined($sym)) {
+	    die("Invalid used of push_locking_hash_tie, should only be called after a lock has occurred and before and unlock.");
+	}
+	push(@pushed_syms,$sym);
+	undef($sym);
+    }
+
+    sub pop_locking_hash_tie {
+	if (defined($sym)) {
+	    die("Invalid nested used of pop_locking_hash_tie, should only be called after a unlock has occurred.");
+	}
+	$sym = pop(@pushed_syms);
+    }
 
     sub _locking_hash_tie {
 	my ($file_prefix,$namespace,$how,$loghead,$what) = @_;
+	if (defined($sym)) {
+	    die('Nested locking attempted withut proper use of push_locking_hahs_tie, this is unsupportted');
+	}
+
         my $lock_type=LOCK_SH;
 # Are we reading or writing?
         if ($how eq &GDBM_READER()) {
@@ -248,16 +267,22 @@ sub _do_hash_untie {
                open($sym,">>$file_prefix.db.lock");
            }
 # Do a shared lock
-           if (!&flock_sym(LOCK_SH)) { return undef; } 
+           if (!&flock_sym(LOCK_SH)) { 
+	       return undef; 
+	   } 
 # If this is compressed, we will actually need an exclusive lock
 	   if (-e "$file_prefix.db.gz") {
-	       if (!&flock_sym(LOCK_EX)) { return undef; }
+	       if (!&flock_sym(LOCK_EX)) {
+		   return undef;
+	       }
 	   }
         } elsif ($how eq &GDBM_WRCREAT()) {
 # We are writing
            open($sym,">>$file_prefix.db.lock");
 # Writing needs exclusive lock
-           if (!&flock_sym(LOCK_EX)) { return undef; }
+           if (!&flock_sym(LOCK_EX)) {
+	       return undef;
+	   }
         } else {
            die("Unknown method $how for $file_prefix");
         }