8335269: [Graal] occasional timeout in java/lang/StringBuffer/TestSynchronization.java with loom

Reviewed-by: dholmes, alanb

src/hotspot/share/runtime/continuationFreezeThaw.cpp

@@ -1579,6 +1579,11 @@ static inline int freeze_internal(JavaThread* current, intptr_t* const sp) {
     verify_continuation(cont.continuation());
     freeze_result res = entry->is_pinned() ? freeze_pinned_cs : freeze_pinned_monitor;
     log_develop_trace(continuations)("=== end of freeze (fail %d)", res);
+    // Avoid Thread.yield() loops without safepoint polls.
+    if (SafepointMechanism::should_process(current)) {
+      cont.done(); // allow safepoint
+      ThreadInVMfromJava tivmfj(current);
+    }
     return res;
   }
 

test/jdk/java/lang/Thread/virtual/ThreadPollOnYield.java

@@ -0,0 +1,79 @@
+/*
+ * Copyright (c) 2024, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test id=default
+ * @bug 8335269
+ * @summary Test that Thread.yield loop polls for safepoints
+ * @requires vm.continuations
+ * @library /test/lib
+ * @run junit/othervm ThreadPollOnYield
+ */
+
+/*
+ * @test id=c2
+ * @bug 8335269
+ * @summary Test that Thread.yield loop polls for safepoints
+ * @requires vm.continuations & vm.compMode != "Xcomp"
+ * @library /test/lib
+ * @run junit/othervm -Xcomp -XX:-TieredCompilation -XX:CompileCommand=inline,*::yield* -XX:CompileCommand=inline,*::*Yield ThreadPollOnYield
+ */
+
+import java.util.concurrent.atomic.AtomicBoolean;
+
+import jdk.test.lib.thread.VThreadPinner;
+import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.*;
+
+class ThreadPollOnYield {
+    static void foo(AtomicBoolean done) {
+        while (!done.get()) {
+            Thread.yield();
+        }
+    }
+
+    @Test
+    void testThreadYieldPolls() throws Exception {
+        AtomicBoolean done = new AtomicBoolean();
+        var vthread = Thread.ofVirtual().start(() -> {
+            VThreadPinner.runPinned(() -> foo(done));
+        });
+        Thread.sleep(5000);
+        done.set(true);
+        vthread.join();
+
+        System.out.println("First vthread done");
+
+        AtomicBoolean done2 = new AtomicBoolean();
+        vthread = Thread.ofVirtual().start(() -> {
+            VThreadPinner.runPinned(() -> foo(done2));
+        });
+        long start = System.currentTimeMillis();
+        while (System.currentTimeMillis() - start < 5000) {
+            Thread.sleep(250);
+            System.gc();
+        }
+        done2.set(true);
+        vthread.join();
+    }
+}