notify Truffle debugger session when a thread is resumed to ensure the stepping strategy is always cleared

Author: javeleon

espresso/src/com.oracle.truffle.espresso.jdwp/src/com/oracle/truffle/espresso/jdwp/api/JDWPContext.java

@@ -502,5 +502,7 @@ public interface JDWPContext {
 
     void steppingInProgress(Thread t, boolean value);
 
+    boolean isSteppingInProgress(Thread t);
+
     void replaceController(DebuggerController newController);
 }

espresso/src/com.oracle.truffle.espresso.jdwp/src/com/oracle/truffle/espresso/jdwp/impl/DebuggerController.java

@@ -510,6 +510,22 @@ public boolean resume(Object thread) {
 
                 fine(() -> "Waking up thread: " + getThreadName(thread));
                 threadSuspension.removeHardSuspendedThread(thread);
+
+                Thread hostThread = context.asHostThread(thread);
+                if (!context.isSteppingInProgress(hostThread)) {
+                    // We need to notify the Truffle debugger session that this thread is resumed.
+                    // Otherwise, we risk losing an update to the stepping strategy, which causes a
+                    // major slowdown due to frame materialization required for e.g. onReturn
+                    // notifications.
+                    fine(() -> "calling underlying resume method for guestThread: " + getThreadName(thread));
+
+                    try {
+                        debuggerSession.resume(hostThread);
+                    } catch (IllegalStateException e) {
+                        // debugger session is closed. Safe to ignore
+                    }
+                }
+
                 lock.release();
                 lock.notifyAll();
                 return true;

espresso/src/com.oracle.truffle.espresso/src/com/oracle/truffle/espresso/runtime/EspressoThreadLocalState.java

@@ -137,6 +137,10 @@ public void setSteppingInProgress(boolean value) {
         stepInProgress = value;
     }
 
+    public boolean isSteppingInProgress() {
+        return stepInProgress;
+    }
+
     public boolean disableSingleStepping(boolean forceDisable) {
         if (forceDisable || stepInProgress) {
             singleSteppingDisabledCounter++;

espresso/src/com.oracle.truffle.espresso/src/com/oracle/truffle/espresso/runtime/JDWPContextImpl.java

@@ -284,6 +284,17 @@ public void steppingInProgress(Thread t, boolean value) {
         }
     }
 
+    @Override
+    public boolean isSteppingInProgress(Thread t) {
+        Object previous = null;
+        try {
+            previous = controller.enterTruffleContext();
+            return context.getLanguage().getThreadLocalStateFor(t).isSteppingInProgress();
+        } finally {
+            controller.leaveTruffleContext(previous);
+        }
+    }
+
     @Override
     public Object[] getAllGuestThreads() {
         StaticObject[] activeThreads = context.getActiveThreads();