[GR-18163] Share a Fiber as soon as it's created and sharing is enabled

PullRequest: truffleruby/4379

spec/truffle/thread_safe_objects_spec.rb

@@ -463,6 +463,18 @@ def wb; @wb; end
     end.join
   end
 
+  it "Fiber which refers to an Array via instance variables" do
+    a = [Object.new]
+    f = Fiber.new { 42 }
+    shared?(f).should == true
+
+    f.instance_variable_set(:@a, a)
+    shared?(a).should == true
+    shared?(a[0]).should == true
+
+    f.resume.should == 42
+  end
+
   it "Thread local variables which share the value (probably they should not)" do
     thread = Thread.current
     shared?(thread).should == true

src/main/java/org/truffleruby/core/fiber/FiberManager.java

@@ -41,7 +41,6 @@
 import com.oracle.truffle.api.CompilerDirectives;
 import com.oracle.truffle.api.CompilerDirectives.TruffleBoundary;
 import com.oracle.truffle.api.nodes.Node;
-import com.oracle.truffle.api.source.SourceSection;
 import org.truffleruby.language.objects.shared.SharedObjects;
 
 /** Helps managing Ruby {@code Fiber} objects. Only one per {@link RubyContext}. */
@@ -58,14 +57,6 @@ public FiberManager(RubyLanguage language, RubyContext context) {
         this.context = context;
     }
 
-    public void initialize(RubyFiber fiber, boolean blocking, RubyProc block, Node currentNode) {
-        final SourceSection sourceSection = block.getSharedMethodInfo().getSourceSection();
-        fiber.sourceLocation = context.fileLine(sourceSection);
-        fiber.body = block;
-        fiber.initializeNode = currentNode;
-        fiber.blocking = blocking;
-    }
-
     private void createThreadToReceiveFirstMessage(RubyFiber fiber, Node currentNode) {
         assert fiber.thread == null;
         RubyProc block = Objects.requireNonNull(fiber.body);
@@ -347,8 +338,10 @@ public void start(RubyFiber fiber, Thread javaThread) {
 
         final RubyThread rubyThread = fiber.rubyThread;
 
-        // share RubyFiber as its fiberLocals might be accessed by other threads with Thread#[]
-        SharedObjects.propagate(language, rubyThread, fiber);
+        // The RubyFiber has been shared in RubyFiber#initialize,
+        // or by ThreadManager#startSharing for the root Fiber of a RubyThread.
+        assert !SharedObjects.isShared(rubyThread) || SharedObjects.isShared(fiber);
+
         rubyThread.runningFibers.add(fiber);
     }
 

src/main/java/org/truffleruby/core/fiber/FiberNodes.java

@@ -121,7 +121,7 @@ Object initialize(RubyFiber fiber, boolean blocking, RubyProc block) {
                         coreExceptions().securityError("fibers not allowed with allowCreateThread(false)", this));
             }
 
-            getContext().fiberManager.initialize(fiber, blocking, block, this);
+            fiber.initialize(getLanguage(), getContext(), blocking, block, this);
             return nil;
         }
 

src/main/java/org/truffleruby/core/fiber/RubyFiber.java

@@ -17,6 +17,7 @@
 import com.oracle.truffle.api.CompilerAsserts;
 import com.oracle.truffle.api.exception.AbstractTruffleException;
 import com.oracle.truffle.api.nodes.Node;
+import com.oracle.truffle.api.source.SourceSection;
 import org.truffleruby.RubyContext;
 import org.truffleruby.RubyLanguage;
 import org.truffleruby.cext.ValueWrapperManager;
@@ -36,6 +37,7 @@
 
 import com.oracle.truffle.api.CompilerDirectives.TruffleBoundary;
 import com.oracle.truffle.api.object.Shape;
+import org.truffleruby.language.objects.shared.SharedObjects;
 
 import static org.truffleruby.language.RubyBaseNode.nil;
 
@@ -131,6 +133,18 @@ public RubyFiber(
         handleData = new ValueWrapperManager.HandleBlockHolder();
     }
 
+    public void initialize(RubyLanguage language, RubyContext context, boolean blocking, RubyProc block,
+            Node currentNode) {
+        final SourceSection sourceSection = block.getSharedMethodInfo().getSourceSection();
+        this.sourceLocation = context.fileLine(sourceSection);
+        this.body = block;
+        this.initializeNode = currentNode;
+        this.blocking = blocking;
+
+        // share RubyFiber as its fiberLocals might be accessed by other threads with Thread#[]
+        SharedObjects.propagate(language, this.rubyThread, this);
+    }
+
     public boolean isRootFiber() {
         return rubyThread.getRootFiber() == this;
     }

src/main/java/org/truffleruby/core/thread/RubyThread.java

@@ -147,6 +147,7 @@ public void getAdjacentObjects(Set<Object> reachable) {
         ObjectGraph.addProperty(reachable, threadLocalVariables);
         ObjectGraph.addProperty(reachable, name);
         // share fibers of a thread as its fiberLocals might be accessed by other threads with Thread#[]
+        reachable.add(rootFiber);
         reachable.addAll(runningFibers);
     }