Merge pull request #314 from cvogt/fix-update-bugs

better caching and change propagation fixing link-time errors

8 files changed, 327 insertions, 224 deletions

diff --git a/nailgun_launcher/BuildStage1Result.java b/nailgun_launcher/BuildStage1Result.java
index 312871d..64a660d 100644
--- a/nailgun_launcher/BuildStage1Result.java
+++ b/nailgun_launcher/BuildStage1Result.java
@@ -1,12 +1,14 @@
 package cbt;
 public class BuildStage1Result{
-  public Boolean changed;
+  public long start;
+  public long stage1LastModified;
   public ClassLoader classLoader;
   public String stage1Classpath;
   public String nailgunClasspath;
   public String compatibilityClasspath;
-  public BuildStage1Result( Boolean changed, ClassLoader classLoader, String stage1Classpath, String nailgunClasspath, String compatibilityClasspath ){
-    this.changed = changed;
+  public BuildStage1Result( long start, long stage1LastModified, ClassLoader classLoader, String stage1Classpath, String nailgunClasspath, String compatibilityClasspath ){
+    this.start = start;
+    this.stage1LastModified = stage1LastModified;
     this.classLoader = classLoader;
     this.stage1Classpath = stage1Classpath;
     this.nailgunClasspath = nailgunClasspath;
diff --git a/nailgun_launcher/CbtURLClassLoader.java b/nailgun_launcher/CbtURLClassLoader.java
index 38fc905..bf698b0 100644
--- a/nailgun_launcher/CbtURLClassLoader.java
+++ b/nailgun_launcher/CbtURLClassLoader.java
@@ -15,30 +15,29 @@ public class CbtURLClassLoader extends java.net.URLClassLoader{
       + "\n)"
     );
   }
-  ClassLoaderCache2<Class> cache = new ClassLoaderCache2<Class>(
-    new ConcurrentHashMap<String, Object>(),
-    new ConcurrentHashMap<Object, Class>()
-  );
+  ConcurrentHashMap<String,Class> cache = new ConcurrentHashMap<String,Class>();
   public Class loadClass(String name) throws ClassNotFoundException{
     Class _class = super.loadClass(name);
     if(_class == null) throw new ClassNotFoundException(name);
     else return _class;
   }
-  public Class loadClass(String name, Boolean resolve) throws ClassNotFoundException{
+  public Class loadClass(String name, boolean resolve) throws ClassNotFoundException{
     //System.out.println("loadClass("+name+") on \n"+this);
-    if(!cache.contains(name))
-      try{
-        cache.put(super.loadClass(name, resolve), name);
-      } catch (ClassNotFoundException e){
-        cache.put(Object.class, name);
+    synchronized( cache ){
+      if(!cache.containsKey(name))
+        try{
+          cache.put(name, super.loadClass(name, resolve));
+        } catch (ClassNotFoundException e){
+          cache.put(name, Object.class);
+        }
+      Class _class = cache.get(name);
+      if(_class == Object.class){
+        if( name.equals("java.lang.Object") )
+          return Object.class;
+        else return null;
+      } else {
+        return _class;
       }
-    Class _class = cache.get(name);
-    if(_class == Object.class){
-      if( name == "java.lang.Object" )
-        return Object.class;
-      else return null;
-    } else {
-      return _class;
     }
   }
   void assertExist(URL[] urls){
diff --git a/nailgun_launcher/ClassLoaderCache.java b/nailgun_launcher/ClassLoaderCache.java
new file mode 100644
index 0000000..6bffad0
--- /dev/null
+++ b/nailgun_launcher/ClassLoaderCache.java
@@ -0,0 +1,66 @@
+package cbt;
+
+import java.util.*;
+import static java.io.File.pathSeparator;
+import static cbt.Stage0Lib.*;
+
+final public class ClassLoaderCache{
+  public Map<Object,Object> hashMap;
+  final ThreadLocal<HashSet<String>> seen = new ThreadLocal<HashSet<String>>(){
+    @Override protected HashSet<String> initialValue(){
+      return new HashSet<String>();
+    }
+  };
+
+  public ClassLoaderCache(
+    Map<Object,Object> hashMap
+  ){
+    this.hashMap = hashMap;
+  }
+
+  public ClassLoader get( String key, long timestamp ){
+    seen.get().add( key );
+    @SuppressWarnings("unchecked")
+    ClassLoader t = (ClassLoader) hashMap.get(
+      hashMap.get( key )
+    );
+    assert hashMap.get(t).equals(timestamp);
+    return t;
+  }
+
+  public boolean containsKey( String key, long timestamp ){
+    boolean contains = hashMap.containsKey( key );
+    if( contains ){
+      Object keyObject = hashMap.get( key );
+      Object classLoader = hashMap.get( keyObject );
+      long oldTimestamp = (long) hashMap.get( classLoader );
+      boolean res = oldTimestamp == timestamp;
+      return res;
+    } else {
+      return false;
+    }
+  }
+
+  public void put( String key, ClassLoader value, long timestamp ){
+    assert !seen.get().contains( key ): "Thread tries to update cache key after observing it: " + key;
+    LockableJavaKey keyObject = new LockableJavaKey();
+    hashMap.put( key, keyObject );
+    hashMap.put( keyObject, value );
+    hashMap.put( value, timestamp );
+  }
+
+  @Override public String toString(){
+    StringBuilder res = new StringBuilder();
+    res.append("ClassLoaderCache(\n\n");
+    for( Object key: hashMap.keySet() ){
+      if( key instanceof String )
+        res.append(
+          join( "\n", key.toString().split(":") ) + " -> " + hashMap.get( hashMap.get(key) )
+          + "\n\n"
+        );
+    }
+    res.append("\n\n");
+    return res.toString();
+  }
+}
+class LockableJavaKey{}
diff --git a/nailgun_launcher/ClassLoaderCache2.java b/nailgun_launcher/ClassLoaderCache2.java
deleted file mode 100644
index bf9ca3b..0000000
--- a/nailgun_launcher/ClassLoaderCache2.java
+++ /dev/null
@@ -1,37 +0,0 @@
-package cbt;
-
-import java.util.*;
-import java.util.concurrent.ConcurrentHashMap;
-import static java.io.File.pathSeparator;
-import static cbt.Stage0Lib.*;
-
-final class ClassLoaderCache2<T>{
-  ConcurrentHashMap<String,Object> keys;
-  ConcurrentHashMap<Object,T> values;
-
-  public ClassLoaderCache2(
-    ConcurrentHashMap<String,Object> keys,
-    ConcurrentHashMap<Object,T> values
-  ){
-    this.keys = keys;
-    this.values = values;
-  }
-
-  public T get( String key ){
-    return values.get(
-      keys.get( key )
-    );
-  }
-  
-  public Boolean contains( String key ){
-    return keys.containsKey( key );
-  }
-
-  public T put( T value, String key ){
-    LockableKey2 keyObject = new LockableKey2();
-    keys.put( key, keyObject );
-    values.put( keyObject, value );
-    return value;
-  }
-}
-class LockableKey2{}
\ No newline at end of file
diff --git a/nailgun_launcher/EarlyDependencies.java b/nailgun_launcher/EarlyDependencies.java
index 4ffbdfd..8709e69 100644
--- a/nailgun_launcher/EarlyDependencies.java
+++ b/nailgun_launcher/EarlyDependencies.java
@@ -4,6 +4,7 @@ import java.io.*;
 import java.nio.file.*;
 import java.net.*;
 import java.security.*;
+import java.util.*;
 import static cbt.Stage0Lib.*;
 import static cbt.NailgunLauncher.*;
 
@@ -19,125 +20,134 @@ class EarlyDependencies{
   String scalaCompiler_2_11_8_File;
   String scalaXml_1_0_5_File;
   String scalaLibrary_2_11_8_File;
-  String zinc_0_3_9_File;
-  String incrementalCompiler_0_13_9_File;
-  String compilerInterface_0_13_9_File;
-  String scalaCompiler_2_10_5_File;
-  String sbtInterface_0_13_9_File;
-  String scalaReflect_2_10_5_File;
-  String scalaLibrary_2_10_5_File;
+  String zinc_0_3_12_File;
+  String incrementalCompiler_0_13_12_File;
+  String compilerInterface_0_13_12_File;
+  String scalaCompiler_2_10_6_File;
+  String sbtInterface_0_13_12_File;
+  String scalaReflect_2_10_6_File;
+  String scalaLibrary_2_10_6_File;
 
   public EarlyDependencies(
-    String mavenCache, String mavenUrl, ClassLoaderCache2<ClassLoader> classLoaderCache, ClassLoader rootClassLoader
+    String mavenCache, String mavenUrl, ClassLoaderCache classLoaderCache, ClassLoader rootClassLoader
   ) throws Throwable {
     scalaReflect_2_11_8_File = mavenCache + "/org/scala-lang/scala-reflect/2.11.8/scala-reflect-2.11.8.jar";
     scalaCompiler_2_11_8_File = mavenCache + "/org/scala-lang/scala-compiler/2.11.8/scala-compiler-2.11.8.jar";
     scalaXml_1_0_5_File = mavenCache + "/org/scala-lang/modules/scala-xml_2.11/1.0.5/scala-xml_2.11-1.0.5.jar";
     scalaLibrary_2_11_8_File = mavenCache + "/org/scala-lang/scala-library/2.11.8/scala-library-2.11.8.jar";
-    zinc_0_3_9_File = mavenCache + "/com/typesafe/zinc/zinc/0.3.9/zinc-0.3.9.jar";
-    incrementalCompiler_0_13_9_File = mavenCache + "/com/typesafe/sbt/incremental-compiler/0.13.9/incremental-compiler-0.13.9.jar";
-    compilerInterface_0_13_9_File = mavenCache + "/com/typesafe/sbt/compiler-interface/0.13.9/compiler-interface-0.13.9-sources.jar";
-    scalaCompiler_2_10_5_File = mavenCache + "/org/scala-lang/scala-compiler/2.10.5/scala-compiler-2.10.5.jar";
-    sbtInterface_0_13_9_File = mavenCache + "/com/typesafe/sbt/sbt-interface/0.13.9/sbt-interface-0.13.9.jar";
-    scalaReflect_2_10_5_File = mavenCache + "/org/scala-lang/scala-reflect/2.10.5/scala-reflect-2.10.5.jar";
-    scalaLibrary_2_10_5_File = mavenCache + "/org/scala-lang/scala-library/2.10.5/scala-library-2.10.5.jar";
+    zinc_0_3_12_File = mavenCache + "/com/typesafe/zinc/zinc/0.3.12/zinc-0.3.12.jar";
+    incrementalCompiler_0_13_12_File = mavenCache + "/com/typesafe/sbt/incremental-compiler/0.13.12/incremental-compiler-0.13.12.jar";
+    compilerInterface_0_13_12_File = mavenCache + "/com/typesafe/sbt/compiler-interface/0.13.12/compiler-interface-0.13.12-sources.jar";
+    scalaCompiler_2_10_6_File = mavenCache + "/org/scala-lang/scala-compiler/2.10.6/scala-compiler-2.10.6.jar";
+    sbtInterface_0_13_12_File = mavenCache + "/com/typesafe/sbt/sbt-interface/0.13.12/sbt-interface-0.13.12.jar";
+    scalaReflect_2_10_6_File = mavenCache + "/org/scala-lang/scala-reflect/2.10.6/scala-reflect-2.10.6.jar";
+    scalaLibrary_2_10_6_File = mavenCache + "/org/scala-lang/scala-library/2.10.6/scala-library-2.10.6.jar";
 
     download(new URL(mavenUrl + "/org/scala-lang/scala-reflect/2.11.8/scala-reflect-2.11.8.jar"), Paths.get(scalaReflect_2_11_8_File), "b74530deeba742ab4f3134de0c2da0edc49ca361");
     download(new URL(mavenUrl + "/org/scala-lang/scala-compiler/2.11.8/scala-compiler-2.11.8.jar"), Paths.get(scalaCompiler_2_11_8_File), "fe1285c9f7b58954c5ef6d80b59063569c065e9a");
 
-    // org.scala-lang:scala-library:2.10.5
-    download(new URL(mavenUrl + "/org/scala-lang/scala-library/2.10.5/scala-library-2.10.5.jar"), Paths.get(scalaLibrary_2_10_5_File), "57ac67a6cf6fd591e235c62f8893438e8d10431d");
-
-    String[] scalaLibrary_2_10_5_ClasspathArray = new String[]{scalaLibrary_2_10_5_File};
-    String scalaLibrary_2_10_5_Classpath = classpath( scalaLibrary_2_10_5_ClasspathArray );
-    ClassLoader scalaLibrary_2_10_5_ =
-      classLoaderCache.contains( scalaLibrary_2_10_5_Classpath )
-      ? classLoaderCache.get( scalaLibrary_2_10_5_Classpath )
-      : classLoaderCache.put( classLoader( scalaLibrary_2_10_5_File, rootClassLoader ), scalaLibrary_2_10_5_Classpath );
-
-    // org.scala-lang:scala-reflect:2.10.5
-    download(new URL(mavenUrl + "/org/scala-lang/scala-reflect/2.10.5/scala-reflect-2.10.5.jar"), Paths.get(scalaReflect_2_10_5_File), "7392facb48876c67a89fcb086112b195f5f6bbc3");
-
-    String[] scalaReflect_2_10_5_ClasspathArray = new String[]{scalaLibrary_2_10_5_File, scalaReflect_2_10_5_File};
-    String scalaReflect_2_10_5_Classpath = classpath( scalaReflect_2_10_5_ClasspathArray );
-    ClassLoader scalaReflect_2_10_5_ =
-      classLoaderCache.contains( scalaReflect_2_10_5_Classpath )
-      ? classLoaderCache.get( scalaReflect_2_10_5_Classpath )
-      : classLoaderCache.put( classLoader( scalaReflect_2_10_5_File, scalaLibrary_2_10_5_ ), scalaReflect_2_10_5_Classpath );
-
-    // com.typesafe.sbt:sbt-interface:0.13.9
-    download(new URL(mavenUrl + "/com/typesafe/sbt/sbt-interface/0.13.9/sbt-interface-0.13.9.jar"), Paths.get(sbtInterface_0_13_9_File), "29848631415402c81b732e919be88f268df37250");
-
-    String[] sbtInterface_0_13_9_ClasspathArray = new String[]{sbtInterface_0_13_9_File, scalaLibrary_2_10_5_File, scalaReflect_2_10_5_File};
-    String sbtInterface_0_13_9_Classpath = classpath( sbtInterface_0_13_9_ClasspathArray );
-    ClassLoader sbtInterface_0_13_9_ =
-      classLoaderCache.contains( sbtInterface_0_13_9_Classpath )
-      ? classLoaderCache.get( sbtInterface_0_13_9_Classpath )
-      : classLoaderCache.put( classLoader( sbtInterface_0_13_9_File, scalaReflect_2_10_5_ ), sbtInterface_0_13_9_Classpath );
-
-    // org.scala-lang:scala-compiler:2.10.5
-    download(new URL(mavenUrl + "/org/scala-lang/scala-compiler/2.10.5/scala-compiler-2.10.5.jar"), Paths.get(scalaCompiler_2_10_5_File), "f0f5bb444ca26a6e489af3dd35e24f7e2d2d118e");
-
-    String[] scalaCompiler_2_10_5_ClasspathArray = new String[]{sbtInterface_0_13_9_File, scalaCompiler_2_10_5_File, scalaLibrary_2_10_5_File, scalaReflect_2_10_5_File};
-    String scalaCompiler_2_10_5_Classpath = classpath( scalaCompiler_2_10_5_ClasspathArray );
-    ClassLoader scalaCompiler_2_10_5_ =
-      classLoaderCache.contains( scalaCompiler_2_10_5_Classpath )
-      ? classLoaderCache.get( scalaCompiler_2_10_5_Classpath )
-      : classLoaderCache.put( classLoader( scalaCompiler_2_10_5_File, sbtInterface_0_13_9_ ), scalaCompiler_2_10_5_Classpath );
-
-    // com.typesafe.sbt:compiler-interface:0.13.9
-    download(new URL(mavenUrl + "/com/typesafe/sbt/compiler-interface/0.13.9/compiler-interface-0.13.9-sources.jar"), Paths.get(compilerInterface_0_13_9_File), "2311addbed1182916ad00f83c57c0eeca1af382b");
-
-    String[] compilerInterface_0_13_9_ClasspathArray = new String[]{compilerInterface_0_13_9_File, sbtInterface_0_13_9_File, scalaCompiler_2_10_5_File, scalaLibrary_2_10_5_File, scalaReflect_2_10_5_File};
-    String compilerInterface_0_13_9_Classpath = classpath( compilerInterface_0_13_9_ClasspathArray );
-    ClassLoader compilerInterface_0_13_9_ =
-      classLoaderCache.contains( compilerInterface_0_13_9_Classpath )
-      ? classLoaderCache.get( compilerInterface_0_13_9_Classpath )
-      : classLoaderCache.put( classLoader( compilerInterface_0_13_9_File, scalaCompiler_2_10_5_ ), compilerInterface_0_13_9_Classpath );
-
-    // com.typesafe.sbt:incremental-compiler:0.13.9
-    download(new URL(mavenUrl + "/com/typesafe/sbt/incremental-compiler/0.13.9/incremental-compiler-0.13.9.jar"), Paths.get(incrementalCompiler_0_13_9_File), "fbbf1cadbed058aa226643e83543c35de43b13f0");
-
-    String[] incrementalCompiler_0_13_9_ClasspathArray = new String[]{compilerInterface_0_13_9_File, incrementalCompiler_0_13_9_File, sbtInterface_0_13_9_File, scalaCompiler_2_10_5_File, scalaLibrary_2_10_5_File, scalaReflect_2_10_5_File};
-    String incrementalCompiler_0_13_9_Classpath = classpath( incrementalCompiler_0_13_9_ClasspathArray );
-    ClassLoader incrementalCompiler_0_13_9_ =
-      classLoaderCache.contains( incrementalCompiler_0_13_9_Classpath )
-      ? classLoaderCache.get( incrementalCompiler_0_13_9_Classpath )
-      : classLoaderCache.put( classLoader( incrementalCompiler_0_13_9_File, compilerInterface_0_13_9_ ), incrementalCompiler_0_13_9_Classpath );
-
-    // com.typesafe.zinc:zinc:0.3.9
-    download(new URL(mavenUrl + "/com/typesafe/zinc/zinc/0.3.9/zinc-0.3.9.jar"), Paths.get(zinc_0_3_9_File), "46a4556d1f36739879f4b2cc19a73d12b3036e9a");
-
-    String[] zinc_0_3_9_ClasspathArray = new String[]{compilerInterface_0_13_9_File, incrementalCompiler_0_13_9_File, sbtInterface_0_13_9_File, zinc_0_3_9_File, scalaCompiler_2_10_5_File, scalaLibrary_2_10_5_File, scalaReflect_2_10_5_File};
-    String zinc_0_3_9_Classpath = classpath( zinc_0_3_9_ClasspathArray );
-    ClassLoader zinc_0_3_9_ =
-      classLoaderCache.contains( zinc_0_3_9_Classpath )
-      ? classLoaderCache.get( zinc_0_3_9_Classpath )
-      : classLoaderCache.put( classLoader( zinc_0_3_9_File, incrementalCompiler_0_13_9_ ), zinc_0_3_9_Classpath );
+    // org.scala-lang:scala-library:2.10.6
+    String[] scalaLibrary_2_10_6_ClasspathArray = new String[]{scalaLibrary_2_10_6_File};
+    ClassLoader scalaLibrary_2_10_6_ = loadDependency(
+      mavenUrl + "/org/scala-lang/scala-library/2.10.6/scala-library-2.10.6.jar",
+      scalaLibrary_2_10_6_File,
+      "421989aa8f95a05a4f894630aad96b8c7b828732",
+      classLoaderCache,
+      rootClassLoader,
+      scalaLibrary_2_10_6_ClasspathArray
+    );
+
+    // org.scala-lang:scala-reflect:2.10.6
+    String[] scalaReflect_2_10_6_ClasspathArray = new String[]{scalaLibrary_2_10_6_File, scalaReflect_2_10_6_File};
+    ClassLoader scalaReflect_2_10_6_ = loadDependency(
+      mavenUrl + "/org/scala-lang/scala-reflect/2.10.6/scala-reflect-2.10.6.jar",
+      scalaReflect_2_10_6_File,
+      "3259f3df0f166f017ef5b2d385445808398c316c",
+      classLoaderCache,
+      scalaLibrary_2_10_6_,
+      scalaReflect_2_10_6_ClasspathArray
+    );
+
+    // com.typesafe.sbt:sbt-interface:0.13.12
+    String[] sbtInterface_0_13_12_ClasspathArray = new String[]{sbtInterface_0_13_12_File, scalaLibrary_2_10_6_File, scalaReflect_2_10_6_File};
+    ClassLoader sbtInterface_0_13_12_ = loadDependency(
+      mavenUrl + "/com/typesafe/sbt/sbt-interface/0.13.12/sbt-interface-0.13.12.jar",
+      sbtInterface_0_13_12_File,
+      "fcc7875c02f0d4641fac0518121bd71475d3909b",
+      classLoaderCache,
+      scalaReflect_2_10_6_,
+      sbtInterface_0_13_12_ClasspathArray
+    );
+
+    // org.scala-lang:scala-compiler:2.10.6
+    String[] scalaCompiler_2_10_6_ClasspathArray = new String[]{sbtInterface_0_13_12_File, scalaCompiler_2_10_6_File, scalaLibrary_2_10_6_File, scalaReflect_2_10_6_File};
+    ClassLoader scalaCompiler_2_10_6_ = loadDependency(
+      mavenUrl + "/org/scala-lang/scala-compiler/2.10.6/scala-compiler-2.10.6.jar",
+      scalaCompiler_2_10_6_File,
+      "9b15174852f5b6bb1edbf303d5722286a0a54011",
+      classLoaderCache,
+      sbtInterface_0_13_12_,
+      scalaCompiler_2_10_6_ClasspathArray
+    );
+
+    // com.typesafe.sbt:compiler-interface:0.13.12
+    String[] compilerInterface_0_13_12_ClasspathArray = new String[]{compilerInterface_0_13_12_File, sbtInterface_0_13_12_File, scalaCompiler_2_10_6_File, scalaLibrary_2_10_6_File, scalaReflect_2_10_6_File};
+    ClassLoader compilerInterface_0_13_12_ = loadDependency(
+      mavenUrl + "/com/typesafe/sbt/compiler-interface/0.13.12/compiler-interface-0.13.12-sources.jar",
+      compilerInterface_0_13_12_File,
+      "d9c3270576e162bf017b146af262364c2db87a32",
+      classLoaderCache,
+      scalaCompiler_2_10_6_,
+      compilerInterface_0_13_12_ClasspathArray
+    );
+
+    // com.typesafe.sbt:incremental-compiler:0.13.12
+    String[] incrementalCompiler_0_13_12_ClasspathArray = new String[]{compilerInterface_0_13_12_File, incrementalCompiler_0_13_12_File, sbtInterface_0_13_12_File, scalaCompiler_2_10_6_File, scalaLibrary_2_10_6_File, scalaReflect_2_10_6_File};
+    ClassLoader incrementalCompiler_0_13_12_ = loadDependency(
+      mavenUrl + "/com/typesafe/sbt/incremental-compiler/0.13.12/incremental-compiler-0.13.12.jar",
+      incrementalCompiler_0_13_12_File,
+      "259f6d24a5a3791bb233787d6a8e639c4ab86fe5",
+      classLoaderCache,
+      compilerInterface_0_13_12_,
+      incrementalCompiler_0_13_12_ClasspathArray
+    );
+
+    // com.typesafe.zinc:zinc:0.3.12
+    String[] zinc_0_3_12_ClasspathArray = new String[]{compilerInterface_0_13_12_File, incrementalCompiler_0_13_12_File, sbtInterface_0_13_12_File, zinc_0_3_12_File, scalaCompiler_2_10_6_File, scalaLibrary_2_10_6_File, scalaReflect_2_10_6_File};
+    ClassLoader zinc_0_3_12_ = loadDependency(
+      mavenUrl + "/com/typesafe/zinc/zinc/0.3.12/zinc-0.3.12.jar",
+      zinc_0_3_12_File,
+      "c4339e93f5b7273f49ad026248f4fdb1d4d6c7c4",
+      classLoaderCache,
+      incrementalCompiler_0_13_12_,
+      zinc_0_3_12_ClasspathArray
+    );
 
     // org.scala-lang:scala-library:2.11.8
-    download(new URL(mavenUrl + "/org/scala-lang/scala-library/2.11.8/scala-library-2.11.8.jar"), Paths.get(scalaLibrary_2_11_8_File), "ddd5a8bced249bedd86fb4578a39b9fb71480573");
-
     String[] scalaLibrary_2_11_8_ClasspathArray = new String[]{scalaLibrary_2_11_8_File};
-    String scalaLibrary_2_11_8_Classpath = classpath( scalaLibrary_2_11_8_ClasspathArray );
-    ClassLoader scalaLibrary_2_11_8_ =
-      classLoaderCache.contains( scalaLibrary_2_11_8_Classpath )
-      ? classLoaderCache.get( scalaLibrary_2_11_8_Classpath )
-      : classLoaderCache.put( classLoader( scalaLibrary_2_11_8_File, rootClassLoader ), scalaLibrary_2_11_8_Classpath );
+    ClassLoader scalaLibrary_2_11_8_ = loadDependency(
+      mavenUrl + "/org/scala-lang/scala-library/2.11.8/scala-library-2.11.8.jar",
+      scalaLibrary_2_11_8_File,
+      "ddd5a8bced249bedd86fb4578a39b9fb71480573",
+      classLoaderCache,
+      rootClassLoader,
+      scalaLibrary_2_11_8_ClasspathArray
+    );
 
     // org.scala-lang.modules:scala-xml_2.11:1.0.5
-    download(new URL(mavenUrl + "/org/scala-lang/modules/scala-xml_2.11/1.0.5/scala-xml_2.11-1.0.5.jar"), Paths.get(scalaXml_1_0_5_File), "77ac9be4033768cf03cc04fbd1fc5e5711de2459");
-
     String[] scalaXml_1_0_5_ClasspathArray = new String[]{scalaXml_1_0_5_File, scalaLibrary_2_11_8_File};
-    String scalaXml_1_0_5_Classpath = classpath( scalaXml_1_0_5_ClasspathArray );
-    ClassLoader scalaXml_1_0_5_ =
-      classLoaderCache.contains( scalaXml_1_0_5_Classpath )
-      ? classLoaderCache.get( scalaXml_1_0_5_Classpath )
-      : classLoaderCache.put( classLoader( scalaXml_1_0_5_File, scalaLibrary_2_11_8_ ), scalaXml_1_0_5_Classpath );
-  
+    ClassLoader scalaXml_1_0_5_ = loadDependency(
+      mavenUrl + "/org/scala-lang/modules/scala-xml_2.11/1.0.5/scala-xml_2.11-1.0.5.jar",
+      scalaXml_1_0_5_File,
+      "77ac9be4033768cf03cc04fbd1fc5e5711de2459",
+      classLoaderCache,
+      scalaLibrary_2_11_8_,
+      scalaXml_1_0_5_ClasspathArray
+    );
+
     classLoader = scalaXml_1_0_5_;
     classpathArray = scalaXml_1_0_5_ClasspathArray;
 
-    zinc = zinc_0_3_9_;
+    zinc = zinc_0_3_12_;
   }
 }
diff --git a/nailgun_launcher/NailgunLauncher.java b/nailgun_launcher/NailgunLauncher.java
index 944daf8..d89c764 100644
--- a/nailgun_launcher/NailgunLauncher.java
+++ b/nailgun_launcher/NailgunLauncher.java
@@ -4,7 +4,6 @@ import java.lang.reflect.*;
 import java.net.*;
 import java.security.*;
 import java.util.*;
-import java.util.concurrent.ConcurrentHashMap;
 import static cbt.Stage0Lib.*;
 import static java.io.File.pathSeparator;
 
@@ -15,10 +14,7 @@ import static java.io.File.pathSeparator;
  */
 public class NailgunLauncher{
   /** Persistent cache for caching classloaders for the JVM life time. */
-  private final static ClassLoaderCache2<ClassLoader> classLoaderCache = new ClassLoaderCache2<ClassLoader>(
-    new ConcurrentHashMap<String,Object>(),
-    new ConcurrentHashMap<Object,ClassLoader>()
-  );
+  private static Map<Object,Object> classLoaderCacheHashMap = new HashMap<Object,Object>();
 
   public final static SecurityManager initialSecurityManager
     = System.getSecurityManager();
@@ -30,14 +26,13 @@ public class NailgunLauncher{
   @SuppressWarnings("unchecked")
   public static Object getBuild( Object context ) throws Throwable{
     BuildStage1Result res = buildStage1(
-      (Boolean) get(context, "cbtHasChangedCompat"),
-      (Long) get(context, "startCompat"),
+      (long) get(context, "cbtLastModified"),
+      (long) get(context, "start"),
       ((File) get(context, "cache")).toString() + "/",
       ((File) get(context, "cbtHome")).toString(),
       ((File) get(context, "compatibilityTarget")).toString() + "/",
-      new ClassLoaderCache2<ClassLoader>(
-        (ConcurrentHashMap<String,Object>) get(context, "permanentKeys"),
-        (ConcurrentHashMap<Object,ClassLoader>) get(context, "permanentClassLoaders")
+      new ClassLoaderCache(
+        (HashMap) get(context, "persistentCache")
       )
     );
     return
@@ -48,8 +43,16 @@ public class NailgunLauncher{
         .invoke(null, context, res);
   }
 
+  public static long nailgunLauncherLastModified = -1; // this initial value should be overwritten, never read
+
+  // wrap for caching
+  public static ClassLoader jdkClassLoader = new CbtURLClassLoader(
+    new URL[]{},
+    ClassLoader.getSystemClassLoader().getParent()
+  );
+
   public static void main( String[] args ) throws Throwable {
-    Long _start = System.currentTimeMillis();
+    long _start = System.currentTimeMillis();
     if(args[0].equals("check-alive")){
       System.exit(33);
       return;
@@ -65,13 +68,13 @@ public class NailgunLauncher{
     // scala.Console, which captured them at startup
     try{
       System.out.getClass().getDeclaredField("streams"); // nailgun ThreadLocalPrintStream
-      assert(System.out.getClass().getName() == "com.martiansoftware.nailgun.ThreadLocalPrintStream");
+      assert(System.out.getClass().getName().equals("com.martiansoftware.nailgun.ThreadLocalPrintStream"));
     } catch( NoSuchFieldException e ){
       System.setOut( new PrintStream(new ThreadLocalOutputStream(System.out), true) );
     }
     try{
       System.err.getClass().getDeclaredField("streams"); // nailgun ThreadLocalPrintStream
-      assert(System.err.getClass().getName() == "com.martiansoftware.nailgun.ThreadLocalPrintStream");
+      assert(System.err.getClass().getName().equals("com.martiansoftware.nailgun.ThreadLocalPrintStream"));
     } catch( NoSuchFieldException e ){
       System.setErr( new PrintStream(new ThreadLocalOutputStream(System.err), true) );
     }
@@ -81,28 +84,38 @@ public class NailgunLauncher{
     String CBT_HOME = System.getenv("CBT_HOME");
     String cache = CBT_HOME + "/cache/";
     String compatibilityTarget = CBT_HOME + "/compatibility/" + TARGET;
+    // copy cache, so that this thread has a consistent view despite other threads
+    // changing their copies
+    // replace again before returning, see below
+    ClassLoaderCache classLoaderCache = new ClassLoaderCache(
+      new HashMap<Object,Object>(classLoaderCacheHashMap)
+    );
+
+    String nailgunTarget = CBT_HOME + "/" + NAILGUN + TARGET;
+    long nailgunLauncherLastModified = new File( nailgunTarget + "../classes.last-success" ).lastModified();
+
     BuildStage1Result res = buildStage1(
-      false, start, cache, CBT_HOME, compatibilityTarget, classLoaderCache
+      nailgunLauncherLastModified, start, cache, CBT_HOME, compatibilityTarget, classLoaderCache
     );
 
     try{
-      System.exit(
-        (Integer) res
-          .classLoader
-          .loadClass("cbt.Stage1")
-          .getMethod(
-            "run",
-            String[].class, File.class, File.class, BuildStage1Result.class,
-            Long.class, ConcurrentHashMap.class, ConcurrentHashMap.class
-          )
-          .invoke(
-            null,
-            (Object) args, new File(cache), new File(CBT_HOME), res,
-            start, classLoaderCache.keys, classLoaderCache.values
-          )
-      );
+      int exitCode = (int) res
+        .classLoader
+        .loadClass("cbt.Stage1")
+        .getMethod(
+          "run", String[].class, File.class, File.class, BuildStage1Result.class, Map.class
+        ).invoke(
+          null, (Object) args, new File(cache), new File(CBT_HOME), res, classLoaderCache.hashMap
+        );
+
+      System.exit( exitCode );
     } catch (java.lang.reflect.InvocationTargetException e) {
       throw unwrapInvocationTargetException(e);
+    } finally {
+      // This replaces the cache and should be thread-safe.
+      // For competing threads the last one wins with a consistent cache.
+      // So worst case, we loose some of the cache that's replaced.
+      classLoaderCacheHashMap = classLoaderCache.hashMap;
     }
   }
 
@@ -115,7 +128,8 @@ public class NailgunLauncher{
   }
 
   public static BuildStage1Result buildStage1(
-    Boolean changed, long start, String cache, String cbtHome, String compatibilityTarget, ClassLoaderCache2<ClassLoader> classLoaderCache
+    final long lastModified, final long start, final String cache, final String cbtHome,
+    final String compatibilityTarget, final ClassLoaderCache classLoaderCache
   ) throws Throwable {
     _assert(TARGET != null, "environment variable TARGET not defined");
     String nailgunTarget = cbtHome + "/" + NAILGUN + TARGET;
@@ -128,30 +142,32 @@ public class NailgunLauncher{
     ClassLoader rootClassLoader = new CbtURLClassLoader( new URL[]{}, ClassLoader.getSystemClassLoader().getParent() ); // wrap for caching
     EarlyDependencies earlyDeps = new EarlyDependencies(mavenCache, mavenUrl, classLoaderCache, rootClassLoader);
 
-    ClassLoader compatibilityClassLoader;
+    long nailgunLauncherLastModified = new File( nailgunTarget + "../classes.last-success" ).lastModified();
+
+    long compatibilityLastModified;
     if(!compatibilityTarget.startsWith(cbtHome)){
-      compatibilityClassLoader = classLoaderCache.get( compatibilityTarget );
+      compatibilityLastModified = new File( compatibilityTarget + "../classes.last-success" ).lastModified();
     } else {
       List<File> compatibilitySourceFiles = new ArrayList<File>();
       for( File f: compatibilitySources.listFiles() ){
-        if( f.isFile() && (f.toString().endsWith(".scala") || f.toString().endsWith(".java")) ){
+        if( f.isFile() && f.toString().endsWith(".java") ){
           compatibilitySourceFiles.add(f);
         }
       }
-      changed = compile(changed, start, "", compatibilityTarget, earlyDeps, compatibilitySourceFiles);
-      
-      if( classLoaderCache.contains( compatibilityTarget ) ){
-        compatibilityClassLoader = classLoaderCache.get( compatibilityTarget );
-      } else {
-        compatibilityClassLoader = classLoaderCache.put( classLoader(compatibilityTarget, rootClassLoader), compatibilityTarget );
+
+      compatibilityLastModified = compile( 0L, "", compatibilityTarget, earlyDeps, compatibilitySourceFiles);
+
+      if( !classLoaderCache.containsKey( compatibilityTarget, compatibilityLastModified ) ){
+        classLoaderCache.put( compatibilityTarget, classLoader(compatibilityTarget, rootClassLoader), compatibilityLastModified );
       }
     }
+    final ClassLoader compatibilityClassLoader = classLoaderCache.get( compatibilityTarget, compatibilityLastModified );
 
     String[] nailgunClasspathArray = append( earlyDeps.classpathArray, nailgunTarget );
     String nailgunClasspath = classpath( nailgunClasspathArray );
-    ClassLoader nailgunClassLoader = new CbtURLClassLoader( new URL[]{}, NailgunLauncher.class.getClassLoader() ); // wrap for caching
-    if( !classLoaderCache.contains( nailgunClasspath ) ){
-      nailgunClassLoader = classLoaderCache.put( nailgunClassLoader, nailgunClasspath );
+    final ClassLoader nailgunClassLoader = new CbtURLClassLoader( new URL[]{}, NailgunLauncher.class.getClassLoader() ); // wrap for caching
+    if( !classLoaderCache.containsKey( nailgunClasspath, nailgunLauncherLastModified ) ){
+      classLoaderCache.put( nailgunClasspath, nailgunClassLoader, nailgunLauncherLastModified );
     }
 
     String[] stage1ClasspathArray =
@@ -164,14 +180,24 @@ public class NailgunLauncher{
         stage1SourceFiles.add(f);
       }
     }
-    changed = compile(changed, start, stage1Classpath, stage1Target, earlyDeps, stage1SourceFiles);
 
-    ClassLoader stage1classLoader;
-    if( !changed && classLoaderCache.contains( stage1Classpath ) ){
-      stage1classLoader = classLoaderCache.get( stage1Classpath );
-    } else {
-      stage1classLoader =
+    final long stage1BeforeCompiled = System.currentTimeMillis();
+    final long stage0LastModified = Math.max(
+      lastModified,
+      Math.max( lastModified, compatibilityLastModified )
+    );
+    final long stage1LastModified = compile(
+      stage0LastModified, stage1Classpath, stage1Target, earlyDeps, stage1SourceFiles
+    );
+
+    if( stage1LastModified < compatibilityLastModified )
+      throw new AssertionError(
+        "Cache invalidation bug: cbt compatibility layer recompiled, but cbt stage1 did not."
+      );
+
+    if( !classLoaderCache.containsKey( stage1Classpath, stage1LastModified ) ){
       classLoaderCache.put(
+        stage1Classpath,
         classLoader(
           stage1Target,
           new MultiClassLoader2(
@@ -180,12 +206,14 @@ public class NailgunLauncher{
             earlyDeps.classLoader
           )
         ),
-        stage1Classpath
+        stage1LastModified
       );
     }
+    final ClassLoader stage1classLoader = classLoaderCache.get( stage1Classpath, stage1LastModified );
 
     return new BuildStage1Result(
-      changed,
+      start,
+      stage1LastModified,
       stage1classLoader,
       stage1Classpath,
       nailgunClasspath,
diff --git a/nailgun_launcher/Stage0Lib.java b/nailgun_launcher/Stage0Lib.java
index 452bdae..8237c3c 100644
--- a/nailgun_launcher/Stage0Lib.java
+++ b/nailgun_launcher/Stage0Lib.java
@@ -11,16 +11,17 @@ import static java.io.File.pathSeparator;
 import static cbt.NailgunLauncher.*;
 import java.nio.file.*;
 import java.nio.file.attribute.FileTime;
+import static java.lang.Math.min;
 
 public class Stage0Lib{
-  public static void _assert(Boolean condition, Object msg){
+  public static void _assert(boolean condition, Object msg){
     if(!condition){
       throw new AssertionError("Assertion failed: "+msg);
     }
   }
 
   public static int runMain(String cls, String[] args, ClassLoader cl) throws Throwable{
-    Boolean trapExitCodeBefore = TrapSecurityManager.trapExitCode().get();
+    boolean trapExitCodeBefore = TrapSecurityManager.trapExitCode().get();
     try{
       TrapSecurityManager.trapExitCode().set(true);
       cl.loadClass(cls)
@@ -47,33 +48,65 @@ public class Stage0Lib{
     return join( pathSeparator, files );
   }
 
+  public static long lastModified( String... files ){
+    List<Long> lastModified = new ArrayList<Long>();
+    for( String file: files ){
+      lastModified.add( new File(file).lastModified() );
+    }
+    return Collections.max( lastModified );
+  }
+
+  public static ClassLoader loadDependency(
+    String url,
+    String file,
+    String hash,
+    ClassLoaderCache classLoaderCache,
+    ClassLoader parent,
+    String... classpathArray
+  ) throws Throwable {
+    download(new URL(url), Paths.get(file), hash);
+
+    final long lastModified = lastModified( classpathArray );
+    final String classpath = classpath( classpathArray );
+
+    if( !classLoaderCache.containsKey( classpath, lastModified ) )
+      classLoaderCache.put( classpath, classLoader( file, parent ), lastModified );
+
+    return classLoaderCache.get( classpath, lastModified );
+  }
+
   public static File write(File file, String content, OpenOption... options) throws Throwable{
     file.getParentFile().mkdirs();
     Files.write(file.toPath(), content.getBytes(), options);
     return file;
   }
 
-  public static Boolean compile(
-    Boolean changed, Long start, String classpath, String target,
+  public static long compile(
+    long lastModified, String classpath, String target,
     EarlyDependencies earlyDeps, List<File> sourceFiles
   ) throws Throwable{
     File statusFile = new File( new File(target) + ".last-success" );
-    Long lastSuccessfullCompile = statusFile.lastModified();
+    long lastCompiled = statusFile.lastModified();
+
+    long maxLastModified = lastModified;
+    final long start = System.currentTimeMillis(); // <- before recursing, so we catch them all
+
     for( File file: sourceFiles ){
-      if( file.lastModified() > lastSuccessfullCompile ){
-        changed = true;
-        break;
-      }
+      long l = file.lastModified();
+      if( l > maxLastModified ) maxLastModified = l;
+      // performance optimization because we'll recompile and don't need to check other files
+      if( l > lastCompiled ) break;
     }
-    if(changed){
+
+    if( maxLastModified > lastCompiled ){
       List<String> zincArgs = new ArrayList<String>(
         Arrays.asList(
           new String[]{
             "-scala-compiler", earlyDeps.scalaCompiler_2_11_8_File,
             "-scala-library", earlyDeps.scalaLibrary_2_11_8_File,
             "-scala-extra", earlyDeps.scalaReflect_2_11_8_File,
-            "-sbt-interface", earlyDeps.sbtInterface_0_13_9_File,
-            "-compiler-interface", earlyDeps.compilerInterface_0_13_9_File,
+            "-sbt-interface", earlyDeps.sbtInterface_0_13_12_File,
+            "-compiler-interface", earlyDeps.compilerInterface_0_13_12_File,
             "-cp", classpath,
             "-d", target,
             "-S-deprecation",
@@ -100,8 +133,10 @@ public class Stage0Lib{
       } finally {
         System.setOut(oldOut);
       }
+      return statusFile.lastModified(); // can't just use `start` here as system time precision is less than milliseconds on OSX
+    } else {
+      return lastCompiled;
     }
-    return changed;
   }
 
   public static ClassLoader classLoader( String file ) throws Throwable{
@@ -117,7 +152,7 @@ public class Stage0Lib{
 
   private static String getVarFromEnv(String envKey) {
     String value = System.getenv(envKey);
-    if(value==null || value.isEmpty()) {
+    if(value == null || value.isEmpty()) {
       value = System.getenv(envKey.toUpperCase());
     }
     return value;
@@ -126,7 +161,7 @@ public class Stage0Lib{
   private static void setProxyfromPropOrEnv(String envKey, String propKeyH, String propKeyP) {
     String proxyHost = System.getProperty(propKeyH);
     String proxyPort = System.getProperty(propKeyP);
-    if((proxyHost==null || proxyHost.isEmpty()) && (proxyPort==null || proxyPort.isEmpty())) {
+    if((proxyHost == null || proxyHost.isEmpty()) && (proxyPort == null || proxyPort.isEmpty())) {
       String envVar = getVarFromEnv(envKey);
       if(envVar != null && !envVar.isEmpty()) {
         String[] proxy = envVar.replaceFirst("^https?://", "").split(":", 2);
@@ -140,7 +175,7 @@ public class Stage0Lib{
     setProxyfromPropOrEnv("http_proxy", "http.proxyHost", "http.proxyPort");
     setProxyfromPropOrEnv("https_proxy", "https.proxyHost", "https.proxyPort");
     String nonHosts = System.getProperty("http.nonProxyHosts");
-    if(nonHosts==null || nonHosts.isEmpty()) {
+    if(nonHosts == null || nonHosts.isEmpty()) {
       String envVar = getVarFromEnv("no_proxy");
       if(envVar != null && !envVar.isEmpty()) {
         System.setProperty("http.nonProxyHosts", envVar.replaceAll(",","|"));
diff --git a/nailgun_launcher/TrapSecurityManager.java b/nailgun_launcher/TrapSecurityManager.java
index 48e152b..be59671 100644
--- a/nailgun_launcher/TrapSecurityManager.java
+++ b/nailgun_launcher/TrapSecurityManager.java
@@ -39,7 +39,7 @@ public class TrapSecurityManager extends ProxySecurityManager{
   public TrapSecurityManager(){
     super(NailgunLauncher.initialSecurityManager);
   }
-  
+
   public void checkPermission( Permission permission ){
     /*
     NOTE: is it actually ok, to just make these empty?