Fix Thread.getStackTrace() right after Thread.start().

zakkak · Oct 17, 2023 · 6ed33b8 · 6ed33b8
1 parent 14ca57e
commit 6ed33b8
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Showing 4 changed files with 14 additions and 9 deletions.
diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StackTraceUtils.java
@@ -63,7 +63,6 @@
 import com.oracle.svm.core.thread.JavaVMOperation;
 import com.oracle.svm.core.thread.LoomSupport;
 import com.oracle.svm.core.thread.PlatformThreads;
-import com.oracle.svm.core.thread.Target_java_lang_Thread;
 import com.oracle.svm.core.thread.Target_jdk_internal_vm_Continuation;
 import com.oracle.svm.core.thread.VMOperation;
 import com.oracle.svm.core.thread.VirtualThreads;
@@ -113,6 +112,9 @@ public static StackTraceElement[] getStackTraceAtSafepoint(Thread thread) {
 
     public static StackTraceElement[] getThreadStackTraceAtSafepoint(IsolateThread isolateThread, Pointer endSP) {
         assert VMOperation.isInProgressAtSafepoint();
+        if (isolateThread.isNull()) { // recently launched thread
+            return NO_ELEMENTS;
+        }
         BuildStackTraceVisitor visitor = new BuildStackTraceVisitor(false, SubstrateOptions.maxJavaStackTraceDepth());
         JavaStackWalker.walkThread(isolateThread, endSP, visitor, null);
         return visitor.trace.toArray(NO_ELEMENTS);
@@ -232,6 +234,10 @@ public static ClassLoader latestUserDefinedClassLoader(Pointer startSP) {
     }
 
     public static StackTraceElement[] asyncGetStackTrace(Thread thread) {
+        if (!thread.isAlive()) {
+            /* Avoid triggering a safepoint operation below if the thread is not even alive. */
+            return NO_ELEMENTS;
+        }
         GetStackTraceOperation vmOp = new GetStackTraceOperation(thread);
         vmOp.enqueue();
         return vmOp.result;
@@ -248,11 +254,7 @@ private static class GetStackTraceOperation extends JavaVMOperation {
 
         @Override
         protected void operate() {
-            if (thread.isAlive()) {
-                result = getStackTraceAtSafepoint(thread);
-            } else {
-                result = Target_java_lang_Thread.EMPTY_STACK_TRACE;
-            }
+            result = getStackTraceAtSafepoint(thread);
         }
     }
 

diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/stack/JavaStackWalker.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/stack/JavaStackWalker.java
@@ -293,6 +293,7 @@ public static boolean walkThread(IsolateThread thread, ParameterizedStackFrameVi
 
     @Uninterruptible(reason = "Prevent deoptimization of stack frames while in this method.")
     public static boolean walkThread(IsolateThread thread, Pointer endSP, ParameterizedStackFrameVisitor visitor, Object data) {
+        assert thread.isNonNull();
         JavaStackWalk walk = StackValue.get(JavaStackWalk.class);
         if (initWalk(walk, thread)) {
             walk.setEndSP(endSP);

diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/thread/PlatformThreads.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/thread/PlatformThreads.java
@@ -297,10 +297,12 @@ public static IsolateThread getIsolateThreadUnsafe(Thread t) {
      * Returns the isolate thread associated with a Java thread. The caller must own the
      * {@linkplain VMThreads#THREAD_MUTEX threads mutex} and release it only after it has finished
      * using the returned {@link IsolateThread} pointer.
+     *
+     * This method can return {@code NULL} if the thread is not alive or if it has been recently
+     * started but has not completed initialization yet.
      */
     public static IsolateThread getIsolateThread(Thread t) {
         VMThreads.guaranteeOwnsThreadMutex("Threads mutex must be locked before accessing/iterating the thread list.");
-        VMError.guarantee(t.isAlive(), "Only running java.lang.Thread objects have a IsolateThread");
         return getIsolateThreadUnsafe(t);
     }
 

diff --git a/...atevm/src/com.oracle.svm.core/src/com/oracle/svm/core/thread/Target_java_lang_Thread.java b/...atevm/src/com.oracle.svm.core/src/com/oracle/svm/core/thread/Target_java_lang_Thread.java
@@ -64,8 +64,8 @@
 public final class Target_java_lang_Thread {
 
     // Checkstyle: stop
-    @Alias //
-    public static StackTraceElement[] EMPTY_STACK_TRACE;
+    @Delete //
+    static StackTraceElement[] EMPTY_STACK_TRACE;
 
     @Alias //
     static int NO_INHERIT_THREAD_LOCALS;