Fix stack walking of crashed threads.

Author: christianhaeubl

substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/locks/VMMutex.java

@@ -24,7 +24,6 @@
  */
 package com.oracle.svm.core.locks;
 
-import jdk.graal.compiler.word.Word;
 import org.graalvm.nativeimage.CurrentIsolate;
 import org.graalvm.nativeimage.IsolateThread;
 import org.graalvm.nativeimage.Platform;
@@ -35,6 +34,8 @@
 import com.oracle.svm.core.c.CIsolateDataFactory;
 import com.oracle.svm.core.util.VMError;
 
+import jdk.graal.compiler.word.Word;
+
 /**
  * A mutex that has minimal requirements on Java code. The implementation does not perform memory
  * allocation, exception unwinding, or other complicated operations. This allows it to be used in
@@ -56,6 +57,7 @@ public class VMMutex extends VMLockingPrimitive {
     private final String name;
     IsolateThread owner;
 
+    @Deprecated
     @Platforms(Platform.HOSTED_ONLY.class)
     public VMMutex() {
         this.name = CIsolateDataFactory.getUnspecifiedSuffix();

substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/stack/JavaStackWalker.java

@@ -26,8 +26,6 @@
 
 import static com.oracle.svm.core.Uninterruptible.CALLED_FROM_UNINTERRUPTIBLE_CODE;
 
-import com.oracle.svm.core.deopt.DeoptimizationSlotPacking;
-import jdk.graal.compiler.word.Word;
 import org.graalvm.nativeimage.CurrentIsolate;
 import org.graalvm.nativeimage.IsolateThread;
 import org.graalvm.nativeimage.Platform;
@@ -46,6 +44,7 @@
 import com.oracle.svm.core.code.CodeInfoTable;
 import com.oracle.svm.core.code.UntetheredCodeInfo;
 import com.oracle.svm.core.config.ConfigurationValues;
+import com.oracle.svm.core.deopt.DeoptimizationSlotPacking;
 import com.oracle.svm.core.deopt.DeoptimizedFrame;
 import com.oracle.svm.core.deopt.Deoptimizer;
 import com.oracle.svm.core.heap.RestrictHeapAccess;
@@ -61,6 +60,7 @@
 
 import jdk.graal.compiler.api.replacements.Fold;
 import jdk.graal.compiler.core.common.NumUtil;
+import jdk.graal.compiler.word.Word;
 
 /**
  * Provides methods to iterate over the physical Java stack frames of a thread (native stack frames
@@ -203,14 +203,24 @@ public static void initializeForContinuation(JavaStackWalk walk, StoredContinuat
 
     @Uninterruptible(reason = "Prevent deoptimization of stack frames while in this method.", callerMustBe = true)
     private static void initializeFromFrameAnchor(JavaStackWalk walk, IsolateThread thread, Pointer endSP) {
+        assert thread.isNonNull();
         assert thread != CurrentIsolate.getCurrentThread() : "Walking the stack without specifying a start SP is only allowed when walking other threads";
+        assert VMOperation.isInProgressAtSafepoint() : "Walking the stack of another thread is only safe when that thread is stopped at a safepoint";
 
         JavaFrameAnchor frameAnchor = JavaFrameAnchors.getFrameAnchor(thread);
-        if (frameAnchor.isNull()) {
-            /* Threads that do not have a frame anchor at a safepoint are not walkable. */
+        if (frameAnchor.isNull() || SafepointBehavior.isCrashedThread(thread)) {
+            /*
+             * Threads that do not have a frame anchor at a safepoint are not walkable. This can for
+             * example happen for attached threads that do not have any Java frames at the moment.
+             * Threads that are marked as crashed are also not walkable because they may no longer
+             * have a stack. For such threads, we must not access any data in the frame anchor (as
+             * it is a stack allocated struct).
+             */
             markAsNotWalkable(walk);
         } else {
-            initWalk(walk, thread, frameAnchor.getLastJavaSP(), endSP, frameAnchor.getLastJavaIP(), frameAnchor.getPreviousAnchor());
+            Pointer startSP = frameAnchor.getLastJavaSP();
+            assert startSP.isNonNull();
+            initWalk0(walk, startSP, endSP, frameAnchor.getLastJavaIP(), frameAnchor.getPreviousAnchor());
         }
     }