--- loncom/LONCAPA.pm	2006/06/27 14:49:29	1.9
+++ loncom/LONCAPA.pm	2006/06/27 21:47:15	1.11
@@ -1,7 +1,7 @@
 # The LearningOnline Network
 # Base routines
 #
-# $Id: LONCAPA.pm,v 1.9 2006/06/27 14:49:29 albertel Exp $
+# $Id: LONCAPA.pm,v 1.11 2006/06/27 21:47:15 albertel Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -228,11 +228,30 @@ sub _do_hash_untie {
 
 {
     my $sym;
+    my @pushed_syms;
+
+    sub clean_sym {
+	undef($sym);
+    }
+    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, this is unsupportted');
+	    die('Nested locking attempted without proper use of push_locking_hash_tie, this is unsupported');
 	}
 
         my $lock_type=LOCK_SH;
@@ -246,6 +265,7 @@ sub _do_hash_untie {
                if ((! -e "$file_prefix.db") && (! -e "$file_prefix.db.gz")) {
 # No such file. Forget it.                
                    $! = 2;
+		   &clean_sym();
                    return undef;
                }
 # Apparently just no lock file yet. Make one
@@ -253,11 +273,13 @@ sub _do_hash_untie {
            }
 # Do a shared lock
            if (!&flock_sym(LOCK_SH)) { 
+	       &clean_sym();
 	       return undef; 
 	   } 
 # If this is compressed, we will actually need an exclusive lock
 	   if (-e "$file_prefix.db.gz") {
 	       if (!&flock_sym(LOCK_EX)) {
+		   &clean_sym();
 		   return undef;
 	       }
 	   }
@@ -266,6 +288,7 @@ sub _do_hash_untie {
            open($sym,">>$file_prefix.db.lock");
 # Writing needs exclusive lock
            if (!&flock_sym(LOCK_EX)) {
+	       &clean_sym();
 	       return undef;
 	   }
         } else {
@@ -311,7 +334,7 @@ sub _do_hash_untie {
 	my $result = untie(%$hashref);
 	flock($sym,LOCK_UN);
 	close($sym);
-	undef($sym);
+	&clean_sym();
 	return $result;
     }
 }