--- loncom/LONCAPA.pm	2006/06/19 10:00:27	1.7
+++ loncom/LONCAPA.pm	2006/07/03 10:26:22	1.12
@@ -1,7 +1,7 @@
 # The LearningOnline Network
 # Base routines
 #
-# $Id: LONCAPA.pm,v 1.7 2006/06/19 10:00:27 albertel Exp $
+# $Id: LONCAPA.pm,v 1.12 2006/07/03 10:26:22 foxr Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -43,6 +43,8 @@ our @ISA = qw (Exporter);
 our @EXPORT = qw(&add_get_param &escape &unescape &tie_domain_hash &untie_domain_hash &tie_user_hash &untie_user_hash &propath);
 my %perlvar;
 
+
+
 # Inputs are a url, and a hash ref of
 # form name => value pairs
 # takes care of properly adding the form name elements and values to the 
@@ -218,9 +220,32 @@ 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 without proper use of push_locking_hash_tie, this is unsupported');
+	}
+
         my $lock_type=LOCK_SH;
 # Are we reading or writing?
         if ($how eq &GDBM_READER()) {
@@ -232,22 +257,32 @@ sub _do_hash_untie {
                if ((! -e "$file_prefix.db") && (! -e "$file_prefix.db.gz")) {
 # No such file. Forget it.                
                    $! = 2;
+		   &clean_sym();
                    return undef;
                }
 # Apparently just no lock file yet. Make one
                open($sym,">>$file_prefix.db.lock");
            }
 # Do a shared lock
-           if (!&flock_sym(LOCK_SH)) { return undef; } 
+           if (!&flock_sym(LOCK_SH)) { 
+	       &clean_sym();
+	       return undef; 
+	   } 
 # If this is compressed, we will actually need an exclusive lock
 	   if (-e "$file_prefix.db.gz") {
-	       if (!&flock_sym(LOCK_EX)) { return undef; }
+	       if (!&flock_sym(LOCK_EX)) {
+		   &clean_sym();
+		   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)) {
+	       &clean_sym();
+	       return undef;
+	   }
         } else {
            die("Unknown method $how for $file_prefix");
         }
@@ -291,7 +326,7 @@ sub _do_hash_untie {
 	my $result = untie(%$hashref);
 	flock($sym,LOCK_UN);
 	close($sym);
-	undef($sym);
+	&clean_sym();
 	return $result;
     }
 }