From 4f6b63abf59c2478968506e0e779d0992323534f Mon Sep 17 00:00:00 2001
From: Oliver Tappe
Date: Mon, 24 Mar 2008 10:41:16 +0000
Subject: * Switched from explicit cleanup functions to "resource acquisition
 by definition",   implemented by the new ScopedResource class. This change
 improves robustness   with respect to signals and unexpected errors and makes
 the code cleaner.

git-svn-id: http://svn.openslx.org/svn/openslx/openslx/trunk@1678 95ad53e4-c205-0410-b2fa-d234c58c8868
---
 lib/OpenSLX/Basics.pm         | 68 +++++---------------------------
 lib/OpenSLX/ScopedResource.pm | 91 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 100 insertions(+), 59 deletions(-)
 create mode 100644 lib/OpenSLX/ScopedResource.pm

(limited to 'lib/OpenSLX')

diff --git a/lib/OpenSLX/Basics.pm b/lib/OpenSLX/Basics.pm
index 230bf72b..9af056e6 100644
--- a/lib/OpenSLX/Basics.pm
+++ b/lib/OpenSLX/Basics.pm
@@ -30,12 +30,10 @@ $VERSION = 1.01;
     &vlog
     &checkParams
     &instantiateClass
-    &addCleanupFunction &removeCleanupFunction
 );
 
 our (%openslxConfig, %cmdlineConfig, %openslxPath);
 
-use sigtrap qw( die normal-signals error-signals );
 use subs qw(die warn);
 
 use open ':utf8';
@@ -139,8 +137,6 @@ my %openslxCmdlineArgs = (
     'verbose-level=i' => \$cmdlineConfig{'verbose-level'},
 );
 
-my %cleanupFunctions;
-
 # filehandle used for logging:
 my $openslxLog = *STDERR;
 
@@ -313,27 +309,20 @@ sub callInSubprocess
 
     my $pid = fork();
     if (!$pid) {
-
-        # child...
-        # ...execute the given function and exit:
-        my $ok = eval { $childFunc->(); 1 };
-        if (!$ok) {
-            print STDERR "*** $@";
-            exit 5;
-        }
+        # child -> execute the given function and exit:
+        eval { $childFunc->(); 1 }
+            or die $@;
         exit 0;
     }
 
-    # parent...
-    # ...pass on interrupt- and terminate-signals to child...
-    local $SIG{INT}  = sub { kill 'INT',  $pid; waitpid($pid, 0); exit $? };
-    local $SIG{TERM} = sub { kill 'TERM', $pid; waitpid($pid, 0); exit $? };
+    # parent -> pass on interrupt- and terminate-signals to child ...
+    $SIG{INT}  = sub { kill 'INT',  $pid; };
+    $SIG{TERM} = sub { kill 'TERM', $pid; };
 
-    # ...and wait for child to do its work:
+    # ... and wait until child has done its work
     waitpid($pid, 0);
-    if ($?) {
-        exit $?;
-    }
+    exit $? if $?;
+
     return;
 }
 
@@ -354,36 +343,6 @@ sub executeInSubprocess
     return $pid;
 }
 
-# ------------------------------------------------------------------------------
-sub addCleanupFunction
-{
-    my $name = shift;
-    my $func = shift;
-
-    $cleanupFunctions{$name} = $func;
-    return;
-}
-
-# ------------------------------------------------------------------------------
-sub removeCleanupFunction
-{
-    my $name = shift;
-
-    delete $cleanupFunctions{$name};
-    return;
-}
-
-# ------------------------------------------------------------------------------
-sub invokeCleanupFunctions
-{
-    my @funcNames = keys %cleanupFunctions;
-    foreach my $name (@funcNames) {
-        vlog(2, "invoking cleanup function '$name'...");
-        $cleanupFunctions{$name}->();
-    }
-    return;
-}
-
 # ------------------------------------------------------------------------------
 sub slxsystem
 {
@@ -426,7 +385,6 @@ sub warn
 # ------------------------------------------------------------------------------
 sub confess
 {
-    invokeCleanupFunctions();
     _doThrowOrWarn('confess', @_);
     return;
 }
@@ -434,7 +392,6 @@ sub confess
 # ------------------------------------------------------------------------------
 sub croak
 {
-    invokeCleanupFunctions();
     _doThrowOrWarn('croak', @_);
     return;
 }
@@ -442,7 +399,6 @@ sub croak
 # ------------------------------------------------------------------------------
 sub die
 {
-    invokeCleanupFunctions();
     _doThrowOrWarn('die', @_);
     return;
 }
@@ -636,10 +592,4 @@ sub instantiateClass
     return $class->new;
 }
 
-# ------------------------------------------------------------------------------
-END 
-{
-    invokeCleanupFunctions() if %cleanupFunctions;
-}
-
 1;
diff --git a/lib/OpenSLX/ScopedResource.pm b/lib/OpenSLX/ScopedResource.pm
new file mode 100644
index 00000000..c905b50a
--- /dev/null
+++ b/lib/OpenSLX/ScopedResource.pm
@@ -0,0 +1,91 @@
+# Copyright (c) 2008 - OpenSLX GmbH
+#
+# This program is free software distributed under the GPL version 2.
+# See http://openslx.org/COPYING
+#
+# If you have any feedback please consult http://openslx.org/feedback and
+# send your suggestions, praise, or complaints to feedback@openslx.org
+#
+# General information about OpenSLX can be found at http://openslx.org/
+# -----------------------------------------------------------------------------
+# ScopedResource.pm
+#    - a helper class that releases resources if the object leaves scope
+# -----------------------------------------------------------------------------
+package OpenSLX::ScopedResource;
+
+use strict;
+use warnings;
+
+our $VERSION = 1.01;        # API-version . implementation-version
+
+# make sure that we catch any signals in order to properly released scoped
+# resources
+use sigtrap qw( die normal-signals error-signals );
+
+use OpenSLX::Basics;
+
+sub new
+{
+    my $class = shift;
+    my $params = shift;
+    
+    checkParams($params, {
+        name    => '!',
+        acquire => '!',
+        release => '!',
+    });
+
+    my $self = {
+        name    => $params->{name},
+        owner   => 0,
+        acquire => $params->{acquire},
+        release => $params->{release},
+    };
+    
+    bless $self, $class;
+    
+    $self->acquire();
+    
+    return $self;
+}
+
+sub acquire
+{
+    my $self = shift;
+
+    # acquire the resource and set ourselves as owner
+    if ($self->{acquire}->()) {
+        vlog(1, "process $$ acquired resource $self->{name}");
+        $self->{owner} = $$;
+    }
+}
+
+sub release
+{
+    my $self = shift;
+
+    # only release the resource if invoked by the owning process
+    vlog(3, "process $$ tries to release resource $self->{name}");
+    return if $self->{owner} != $$;
+    
+    # release the resource and unset owner
+    if ($self->{release}->()) {
+        vlog(1, "process $$ released resource $self->{name}");
+        $self->{owner} = 0;
+    }
+}
+
+sub DESTROY
+{
+    my $self = shift;
+    
+    $self->release();
+    
+    # remove references to functions, in order to release any closures
+    $self->{acquire} = undef;
+    $self->{release} = undef;
+    
+    return;
+}
+
+1;
-- 
cgit v1.2.3-55-g7522