--- loncom/lonnet/perl/lonnet.pm	2001/01/06 16:08:24	1.88
+++ loncom/lonnet/perl/lonnet.pm	2001/01/09 19:55:31	1.89
@@ -83,7 +83,7 @@
 # 11/2,11/14,11/15,11/16,11/20,11/21,11/22,11/25,11/27,
 # 12/02,12/12,12/13,12/14,12/28,12/29 Gerd Kortemeyer
 # 05/01/01 Guy Albertelli
-# 05/01,06/01 Gerd Kortemeyer
+# 05/01,06/01,09/01 Gerd Kortemeyer
 
 package Apache::lonnet;
 
@@ -180,6 +180,11 @@ sub reconlonc {
 
 sub critical {
     my ($cmd,$server)=@_;
+    unless ($hostname{$server}) {
+        &logthis("<font color=blue>WARNING:".
+               " Critical message to unknown server ($server)</font>");
+        return 'no_such_host';
+    }
     my $answer=reply($cmd,$server);
     if ($answer eq 'con_lost') {
         my $pingreply=reply('ping',$server);
@@ -244,7 +249,14 @@ sub appenv {
      unless ($fh=Apache::File->new("$ENV{'user.environment'}")) {
 	return 'error';
      }
+     unless (flock($fh,LOCK_SH)) {
+         &logthis("<font color=blue>WARNING: ".
+                  'Could not obtain shared lock in appenv: '.$!);
+         $fh->close();
+         return 'error: '.$!;
+     }
      @oldenv=<$fh>;
+     $fh->close();
     }
     for (my $i=0; $i<=$#oldenv; $i++) {
         chomp($oldenv[$i]);
@@ -261,7 +273,12 @@ sub appenv {
 	return 'error';
      }
      my $newname;
-     flock($fh,LOCK_EX);
+     unless (flock($fh,LOCK_EX)) {
+         &logthis("<font color=blue>WARNING: ".
+                  'Could not obtain exclusive lock in appenv: '.$!);
+         $fh->close();
+         return 'error: '.$!;
+     }
      foreach $newname (keys %newenv) {
 	 print $fh "$newname=$newenv{$newname}\n";
      }
@@ -285,14 +302,26 @@ sub delenv {
      unless ($fh=Apache::File->new("$ENV{'user.environment'}")) {
 	return 'error';
      }
+     unless (flock($fh,LOCK_SH)) {
+         &logthis("<font color=blue>WARNING: ".
+                  'Could not obtain shared lock in delenv: '.$!);
+         $fh->close();
+         return 'error: '.$!;
+     }
      @oldenv=<$fh>;
+     $fh->close();
     }
     {
      my $fh;
      unless ($fh=Apache::File->new(">$ENV{'user.environment'}")) {
 	return 'error';
      }
-     flock($fh,LOCK_EX);
+     unless (flock($fh,LOCK_EX)) {
+         &logthis("<font color=blue>WARNING: ".
+                  'Could not obtain exclusive lock in delenv: '.$!);
+         $fh->close();
+         return 'error: '.$!;
+     }
      map {
 	 unless ($_=~/^$delthis/) { print $fh $_; }
      } @oldenv;