--- a/hotspot/src/share/vm/classfile/loaderConstraints.cpp	Tue Mar 29 09:43:05 2016 +0200
+++ b/hotspot/src/share/vm/classfile/loaderConstraints.cpp	Tue Mar 29 13:02:16 2016 -0400
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003, 2015, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2016, 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
@@ -111,13 +111,14 @@
       if (klass != NULL &&
           klass->class_loader_data()->is_unloading()) {
         probe->set_klass(NULL);
-        if (TraceLoaderConstraints) {
+        if (log_is_enabled(Info, constraints)) {
           ResourceMark rm;
-          tty->print_cr("[Purging class object from constraint for name %s,"
+          outputStream* out = LogHandle(classload, constraints)::info_stream();
+          out->print_cr("purging class object from constraint for name %s,"
                      " loader list:",
                      probe->name()->as_C_string());
           for (int i = 0; i < probe->num_loaders(); i++) {
-            tty->print_cr("[   [%d]: %s", i,
+            out->print_cr("    [%d]: %s", i,
                           probe->loader_data(i)->loader_name());
           }
         }
@@ -126,9 +127,10 @@
       int n = 0;
       while (n < probe->num_loaders()) {
         if (probe->loader_data(n)->is_unloading()) {
-            if (TraceLoaderConstraints) {
+            if (log_is_enabled(Info, classload, constraints)) {
               ResourceMark rm;
-              tty->print_cr("[Purging loader %s from constraint for name %s",
+              outputStream* out = LogHandle(classload, constraints)::info_stream();
+              out->print_cr("purging loader %s from constraint for name %s",
                             probe->loader_data(n)->loader_name(),
                             probe->name()->as_C_string()
                             );
@@ -140,11 +142,12 @@
           probe->set_loader_data(n, probe->loader_data(num));
           probe->set_loader_data(num, NULL);
 
-            if (TraceLoaderConstraints) {
+            if (log_is_enabled(Info, classload, constraints)) {
               ResourceMark rm;
-              tty->print_cr("[New loader list:");
+              outputStream* out = LogHandle(classload, constraints)::info_stream();
+              out->print_cr("new loader list:");
               for (int i = 0; i < probe->num_loaders(); i++) {
-                tty->print_cr("[   [%d]: %s", i,
+                out->print_cr("    [%d]: %s", i,
                               probe->loader_data(i)->loader_name());
               }
             }
@@ -156,9 +159,10 @@
       }
       // Check whether entry should be purged
       if (probe->num_loaders() < 2) {
-            if (TraceLoaderConstraints) {
+            if (log_is_enabled(Info, classload, constraints)) {
               ResourceMark rm;
-              tty->print("[Purging complete constraint for name %s\n",
+              outputStream* out = LogHandle(classload, constraints)::info_stream();
+              out->print_cr("purging complete constraint for name %s",
                          probe->name()->as_C_string());
             }
 
@@ -227,10 +231,11 @@
         p->set_klass(klass);
         p->set_next(bucket(index));
         set_entry(index, p);
-        if (TraceLoaderConstraints) {
+        if (log_is_enabled(Info, classload, constraints)) {
           ResourceMark rm;
-          tty->print("[Adding new constraint for name: %s, loader[0]: %s,"
-                     " loader[1]: %s ]\n",
+          outputStream* out = LogHandle(classload, constraints)::info_stream();
+          out->print_cr("adding new constraint for name: %s, loader[0]: %s,"
+                     " loader[1]: %s",
                      class_name->as_C_string(),
                      SystemDictionary::loader_name(class_loader1()),
                      SystemDictionary::loader_name(class_loader2())
@@ -240,10 +245,11 @@
         /* constraint already imposed */
         if ((*pp1)->klass() == NULL) {
           (*pp1)->set_klass(klass);
-          if (TraceLoaderConstraints) {
+          if (log_is_enabled(Info, classload, constraints)) {
             ResourceMark rm;
-            tty->print("[Setting class object in existing constraint for"
-                       " name: %s and loader %s ]\n",
+            outputStream* out = LogHandle(classload, constraints)::info_stream();
+            out->print_cr("setting class object in existing constraint for"
+                       " name: %s and loader %s",
                        class_name->as_C_string(),
                        SystemDictionary::loader_name(class_loader1())
                        );
@@ -261,8 +267,9 @@
     }
   }
 
-  if (failure_code != 0 && TraceLoaderConstraints) {
+  if (failure_code != 0 && log_is_enabled(Info, classload, constraints)) {
     ResourceMark rm;
+    outputStream* out = LogHandle(classload, constraints)::info_stream();
     const char* reason = "";
     switch(failure_code) {
     case 1: reason = "the class objects presented by loader[0] and loader[1]"
@@ -273,8 +280,8 @@
               " the stored class object in the constraint"; break;
     default: reason = "unknown reason code";
     }
-    tty->print("[Failed to add constraint for name: %s, loader[0]: %s,"
-               " loader[1]: %s, Reason: %s ]\n",
+    out->print_cr("failed to add constraint for name: %s, loader[0]: %s,"
+               " loader[1]: %s, Reason: %s",
                class_name->as_C_string(),
                SystemDictionary::loader_name(class_loader1()),
                SystemDictionary::loader_name(class_loader2()),
@@ -293,10 +300,11 @@
                                                    Symbol* name) {
   LoaderConstraintEntry* p = *(find_loader_constraint(name, loader));
   if (p && p->klass() != NULL && p->klass() != k()) {
-    if (TraceLoaderConstraints) {
+    if (log_is_enabled(Info, classload, constraints)) {
       ResourceMark rm;
-      tty->print("[Constraint check failed for name %s, loader %s: "
-                 "the presented class object differs from that stored ]\n",
+      outputStream* out = LogHandle(classload, constraints)::info_stream();
+      out->print_cr("constraint check failed for name %s, loader %s: "
+                 "the presented class object differs from that stored",
                  name->as_C_string(),
                  SystemDictionary::loader_name(loader()));
     }
@@ -304,10 +312,11 @@
   } else {
     if (p && p->klass() == NULL) {
       p->set_klass(k());
-      if (TraceLoaderConstraints) {
+      if (log_is_enabled(Info, classload, constraints)) {
         ResourceMark rm;
-        tty->print("[Updating constraint for name %s, loader %s, "
-                   "by setting class object ]\n",
+        outputStream* out = LogHandle(classload, constraints)::info_stream();
+        out->print_cr("updating constraint for name %s, loader %s, "
+                   "by setting class object",
                    name->as_C_string(),
                    SystemDictionary::loader_name(loader()));
       }
@@ -353,13 +362,14 @@
   int num = p->num_loaders();
   p->set_loader(num, loader());
   p->set_num_loaders(num + 1);
-  if (TraceLoaderConstraints) {
+  if (log_is_enabled(Info, classload, constraints)) {
     ResourceMark rm;
-    tty->print("[Extending constraint for name %s by adding loader[%d]: %s %s",
+    outputStream* out = LogHandle(classload, constraints)::info_stream();
+    out->print_cr("extending constraint for name %s by adding loader[%d]: %s %s",
                p->name()->as_C_string(),
                num,
                SystemDictionary::loader_name(loader()),
-               (p->klass() == NULL ? " and setting class object ]\n" : " ]\n")
+               (p->klass() == NULL ? " and setting class object" : "")
                );
   }
   if (p->klass() == NULL) {
@@ -392,18 +402,19 @@
     p1->set_num_loaders(num + 1);
   }
 
-  if (TraceLoaderConstraints) {
+  if (log_is_enabled(Info, classload, constraints)) {
     ResourceMark rm;
-    tty->print_cr("[Merged constraints for name %s, new loader list:",
+    outputStream* out = LogHandle(classload, constraints)::info_stream();
+    out->print_cr("merged constraints for name %s, new loader list:",
                   p1->name()->as_C_string()
                   );
 
     for (int i = 0; i < p1->num_loaders(); i++) {
-      tty->print_cr("[   [%d]: %s", i,
+      out->print_cr("    [%d]: %s", i,
                     p1->loader_data(i)->loader_name());
     }
     if (p1->klass() == NULL) {
-      tty->print_cr("[... and setting class object]");
+      out->print_cr("... and setting class object");
     }
   }
 
@@ -473,7 +484,6 @@
 // Called with the system dictionary lock held
 void LoaderConstraintTable::print() {
   ResourceMark rm;
-
   assert_locked_or_safepoint(SystemDictionary_lock);
   tty->print_cr("Java loader constraints (entries=%d)", _loader_constraint_size);
   for (int cindex = 0; cindex < _loader_constraint_size; cindex++) {

--- a/hotspot/src/share/vm/logging/logTag.hpp	Tue Mar 29 09:43:05 2016 +0200
+++ b/hotspot/src/share/vm/logging/logTag.hpp	Tue Mar 29 13:02:16 2016 -0400
@@ -46,6 +46,7 @@
   LOG_TAG(classunload) /* Trace unloading of classes */ \
   LOG_TAG(classpath) \
   LOG_TAG(compaction) \
+  LOG_TAG(constraints) \
   LOG_TAG(cpu) \
   LOG_TAG(cset) \
   LOG_TAG(defaultmethods) \

--- a/hotspot/src/share/vm/runtime/arguments.cpp	Tue Mar 29 09:43:05 2016 +0200
+++ b/hotspot/src/share/vm/runtime/arguments.cpp	Tue Mar 29 13:02:16 2016 -0400
@@ -420,11 +420,12 @@
 static AliasedLoggingFlag const aliased_logging_flags[] = {
   { "TraceBiasedLocking",        LogLevel::Info,  true,  LOG_TAGS(biasedlocking) },
   { "TraceClassLoading",         LogLevel::Info,  true,  LOG_TAGS(classload) },
-  { "TraceClassLoadingPreorder", LogLevel::Debug,  true,  LOG_TAGS(classload, preorder) },
+  { "TraceClassLoadingPreorder", LogLevel::Debug, true,  LOG_TAGS(classload, preorder) },
   { "TraceClassPaths",           LogLevel::Info,  true,  LOG_TAGS(classpath) },
   { "TraceClassResolution",      LogLevel::Debug, true,  LOG_TAGS(classresolve) },
   { "TraceClassUnloading",       LogLevel::Info,  true,  LOG_TAGS(classunload) },
   { "TraceExceptions",           LogLevel::Info,  true,  LOG_TAGS(exceptions) },
+  { "TraceLoaderConstraints",    LogLevel::Info,  true,  LOG_TAGS(classload, constraints) },
   { "TraceMonitorInflation",     LogLevel::Debug, true,  LOG_TAGS(monitorinflation) },
   { "TraceSafepointCleanupTime", LogLevel::Info,  true,  LOG_TAGS(safepointcleanup) },
   { NULL,                        LogLevel::Off,   false, LOG_TAGS(_NO_TAG) }

--- a/hotspot/src/share/vm/runtime/globals.hpp	Tue Mar 29 09:43:05 2016 +0200
+++ b/hotspot/src/share/vm/runtime/globals.hpp	Tue Mar 29 13:02:16 2016 -0400
@@ -2376,9 +2376,6 @@
   product(bool, IgnoreEmptyClassPaths, false,                               \
           "Ignore empty path elements in -classpath")                       \
                                                                             \
-  product_rw(bool, TraceLoaderConstraints, false,                           \
-          "Trace loader constraints")                                       \
-                                                                            \
   product(size_t, InitialBootClassLoaderMetaspaceSize,                      \
           NOT_LP64(2200*K) LP64_ONLY(4*M),                                  \
           "Initial size of the boot class loader data metaspace")           \

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/test/runtime/logging/LoaderConstraintsTest.java	Tue Mar 29 13:02:16 2016 -0400
@@ -0,0 +1,88 @@
+/*
+ * Copyright (c) 2016, 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 LoaderConstraintsTest
+ * @bug 8149996
+ * @library /testlibrary /runtime/testlibrary
+ * @library classes
+ * @build ClassUnloadCommon test.Empty jdk.test.lib.* jdk.test.lib.OutputAnalyzer jdk.test.lib.ProcessTools
+ * @run driver LoaderConstraintsTest
+ */
+
+import jdk.test.lib.*;
+import java.lang.ref.WeakReference;
+import java.lang.reflect.Method;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+public class LoaderConstraintsTest {
+    private static OutputAnalyzer out;
+    private static ProcessBuilder pb;
+    private static class ClassUnloadTestMain {
+        public static void main(String... args) throws Exception {
+            String className = "test.Empty";
+            ClassLoader cl = ClassUnloadCommon.newClassLoader();
+            Class<?> c = cl.loadClass(className);
+            cl = null; c = null;
+            ClassUnloadCommon.triggerUnloading();
+        }
+    }
+
+    // Use the same command-line heap size setting as ../ClassUnload/UnloadTest.java
+    static ProcessBuilder exec(String... args) throws Exception {
+        List<String> argsList = new ArrayList<>();
+        Collections.addAll(argsList, args);
+        Collections.addAll(argsList, "-Xmn8m");
+        Collections.addAll(argsList, "-Dtest.classes=" + System.getProperty("test.classes","."));
+        Collections.addAll(argsList, ClassUnloadTestMain.class.getName());
+        return ProcessTools.createJavaProcessBuilder(argsList.toArray(new String[argsList.size()]));
+    }
+
+    public static void main(String... args) throws Exception {
+
+        // -XX:+TraceLoaderConstraints
+        pb = exec("-XX:+TraceLoaderConstraints");
+        out = new OutputAnalyzer(pb.start());
+        out.getOutput();
+        out.shouldContain("[classload,constraints] adding new constraint for name: java/lang/Class, loader[0]: jdk/internal/loader/ClassLoaders$AppClassLoader, loader[1]: <bootloader>");
+
+        // -Xlog:classload+constraints=info
+        pb = exec("-Xlog:classload+constraints=info");
+        out = new OutputAnalyzer(pb.start());
+        out.shouldContain("[classload,constraints] adding new constraint for name: java/lang/Class, loader[0]: jdk/internal/loader/ClassLoaders$AppClassLoader, loader[1]: <bootloader>");
+
+        // -XX:-TraceLoaderConstraints
+        pb = exec("-XX:-TraceLoaderConstraints");
+        out = new OutputAnalyzer(pb.start());
+        out.shouldNotContain("[classload,constraints]");
+
+        // -Xlog:classload+constraints=off
+        pb = exec("-Xlog:classload+constraints=off");
+        out = new OutputAnalyzer(pb.start());
+        out.shouldNotContain("[classload,constraints]");
+
+    }
+}