# HG changeset patch
# User ehelin
# Date 1411568960 -7200
#      Wed Sep 24 16:29:20 2014 +0200
# Node ID d527d89ab0fdebbd905f05e6420e31ac7c3b52aa
# Parent  74305fe8f5099ac8566abec130a1058f019465ee
8049599: MetaspaceGC::_capacity_until_GC can overflow

diff --git a/src/share/vm/memory/metaspace.cpp b/src/share/vm/memory/metaspace.cpp
--- a/src/share/vm/memory/metaspace.cpp
+++ b/src/share/vm/memory/metaspace.cpp
@@ -1413,17 +1413,39 @@ size_t MetaspaceGC::capacity_until_GC() 
   size_t value = (size_t)OrderAccess::load_ptr_acquire(&_capacity_until_GC);
   assert(value >= MetaspaceSize, "Not initialied properly?");
   return value;
 }
 
 size_t MetaspaceGC::inc_capacity_until_GC(size_t v) {
   assert_is_size_aligned(v, Metaspace::commit_alignment());
 
-  return (size_t)Atomic::add_ptr(v, &_capacity_until_GC);
+  size_t capacity_until_GC = (size_t) _capacity_until_GC;
+  size_t new_value = capacity_until_GC + v;
+
+  if (new_value < capacity_until_GC) {
+    // the addition wrapped around, set new_value to max value
+    new_value = max_uintx;
+  }
+
+  bool cas_succeeded = false;
+  size_t num_retries = 5; // just to limit the number of CAS attempts
+  for (size_t i = 0; i < num_retries; i++) {
+    intptr_t cmp = (intptr_t) capacity_until_GC;
+    intptr_t swap = (intptr_t) new_value;
+    intptr_t prev = Atomic::cmpxchg_ptr(swap, &_capacity_until_GC, cmp);
+
+    if (prev == cmp) {
+      cas_succeeded = true;
+      break;
+    }
+  }
+
+  // if the CAS did not succeed, just return the current value
+  return cas_succeeded ? new_value : _capacity_until_GC;
 }
 
 size_t MetaspaceGC::dec_capacity_until_GC(size_t v) {
   assert_is_size_aligned(v, Metaspace::commit_alignment());
 
   return (size_t)Atomic::add_ptr(-(intptr_t)v, &_capacity_until_GC);
 }
 
diff --git a/src/share/vm/prims/whitebox.cpp b/src/share/vm/prims/whitebox.cpp
--- a/src/share/vm/prims/whitebox.cpp
+++ b/src/share/vm/prims/whitebox.cpp
@@ -815,16 +815,35 @@ WB_ENTRY(void, WB_FreeMetaspace(JNIEnv* 
   oop class_loader_oop = JNIHandles::resolve(class_loader);
   ClassLoaderData* cld = class_loader_oop != NULL
       ? java_lang_ClassLoader::loader_data(class_loader_oop)
       : ClassLoaderData::the_null_class_loader_data();
 
   MetadataFactory::free_array(cld, (Array<u1>*)(uintptr_t)addr);
 WB_END
 
+WB_ENTRY(jlong, WB_IncMetaspaceCapacityUntilGC(JNIEnv* env, jobject wb, jlong size))
+  if (size < 0) {
+    THROW_MSG_0(vmSymbols::java_lang_IllegalArgumentException(),
+        err_msg("WB_IncMetaspaceCapacityUntilGC: size is negative: " JLONG_FORMAT, size));
+  }
+
+  if (size > (jlong) ((size_t) -1)) {
+    THROW_MSG_0(vmSymbols::java_lang_IllegalArgumentException(),
+        err_msg("WB_IncMetaspaceCapacityUntilGC: size does not fit in size_t: " JLONG_FORMAT, size));
+  }
+
+  size_t new_val = MetaspaceGC::inc_capacity_until_GC(align_size_down((size_t) size, Metaspace::commit_alignment()));
+  return (jlong) new_val;
+WB_END
+
+WB_ENTRY(jlong, WB_MetaspaceCapacityUntilGC(JNIEnv* env, jobject wb))
+  return (jlong) MetaspaceGC::capacity_until_GC();
+WB_END
+
 //Some convenience methods to deal with objects from java
 int WhiteBox::offset_for_field(const char* field_name, oop object,
     Symbol* signature_symbol) {
   assert(field_name != NULL && strlen(field_name) > 0, "Field name not valid");
   Thread* THREAD = Thread::current();
 
   //Get the class of our object
   Klass* arg_klass = object->klass();
@@ -986,16 +1005,18 @@ static JNINativeMethod methods[] = {
   {CC"isInStringTable",    CC"(Ljava/lang/String;)Z", (void*)&WB_IsInStringTable  },
   {CC"fullGC",   CC"()V",                             (void*)&WB_FullGC },
   {CC"youngGC",  CC"()V",                             (void*)&WB_YoungGC },
   {CC"readReservedMemory", CC"()V",                   (void*)&WB_ReadReservedMemory },
   {CC"allocateMetaspace",
      CC"(Ljava/lang/ClassLoader;J)J",                 (void*)&WB_AllocateMetaspace },
   {CC"freeMetaspace",
      CC"(Ljava/lang/ClassLoader;JJ)V",                (void*)&WB_FreeMetaspace },
+  {CC"incMetaspaceCapacityUntilGC", CC"(J)J",         (void*)&WB_IncMetaspaceCapacityUntilGC },
+  {CC"metaspaceCapacityUntilGC", CC"()J",             (void*)&WB_MetaspaceCapacityUntilGC },
   {CC"getCPUFeatures",     CC"()Ljava/lang/String;",  (void*)&WB_GetCPUFeatures     },
   {CC"getNMethod",         CC"(Ljava/lang/reflect/Executable;Z)[Ljava/lang/Object;",
                                                       (void*)&WB_GetNMethod         },
   {CC"getThreadStackSize", CC"()J",                   (void*)&WB_GetThreadStackSize },
   {CC"getThreadRemainingStackSize", CC"()J",          (void*)&WB_GetThreadRemainingStackSize },
 };
 
 #undef CC
diff --git a/test/gc/metaspace/TestCapacityUntilGCWrapAround.java b/test/gc/metaspace/TestCapacityUntilGCWrapAround.java
new file mode 100644
--- /dev/null
+++ b/test/gc/metaspace/TestCapacityUntilGCWrapAround.java
@@ -0,0 +1,58 @@
+/*
+ * Copyright (c) 2014, 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
+ * @key gc
+ * @bug 8049831
+ * @library /testlibrary /testlibrary/whitebox
+ * @build TestCapacityUntilGCWrapAround
+ * @run main ClassFileInstaller sun.hotspot.WhiteBox
+ *                              sun.hotspot.WhiteBox$WhiteBoxPermission
+ * @run main/othervm -Xbootclasspath/a:. -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI TestCapacityUntilGCWrapAround
+ */
+
+import sun.hotspot.WhiteBox;
+
+import com.oracle.java.testlibrary.Asserts;
+import com.oracle.java.testlibrary.Platform;
+
+public class TestCapacityUntilGCWrapAround {
+    private static long MB = 1024 * 1024;
+    private static long GB = 1024 * MB;
+    private static long MAX_UINT = 4 * GB - 1; // On 32-bit platforms
+
+    public static void main(String[] args) {
+        if (Platform.is32bit()) {
+            WhiteBox wb = WhiteBox.getWhiteBox();
+
+            long before = wb.metaspaceCapacityUntilGC();
+            long after = wb.incMetaspaceCapacityUntilGC(MAX_UINT);
+
+            Asserts.assertGTE(after, before,
+                String.format("Increasing with MAX_UINT should not cause wrap around: %d < %d", after, before));
+            Asserts.assertEQ(after, MAX_UINT,
+                String.format("Increasing with MAX_UINT should set Metaspace::_capacityUntilGC to max_uint, not: %d", after));
+        }
+    }
+}
diff --git a/test/testlibrary/whitebox/sun/hotspot/WhiteBox.java b/test/testlibrary/whitebox/sun/hotspot/WhiteBox.java
--- a/test/testlibrary/whitebox/sun/hotspot/WhiteBox.java
+++ b/test/testlibrary/whitebox/sun/hotspot/WhiteBox.java
@@ -147,16 +147,18 @@ public class WhiteBox {
 
   // Intered strings
   public native boolean isInStringTable(String str);
 
   // Memory
   public native void readReservedMemory();
   public native long allocateMetaspace(ClassLoader classLoader, long size);
   public native void freeMetaspace(ClassLoader classLoader, long addr, long size);
+  public native long incMetaspaceCapacityUntilGC(long increment);
+  public native long metaspaceCapacityUntilGC();
 
   // force Young GC
   public native void youngGC();
 
   // force Full GC
   public native void fullGC();
 
   // Tests on ReservedSpace/VirtualSpace classes
# HG changeset patch
# User ehelin
# Date 1411568964 -7200
#      Wed Sep 24 16:29:24 2014 +0200
# Node ID 39b8dfa5571426df8f8d236e0a2158e0f7472c8f
# Parent  d527d89ab0fdebbd905f05e6420e31ac7c3b52aa
8049599: MetaspaceGC::_capacity_until_GC can overflow (01)

diff --git a/src/share/vm/memory/metaspace.cpp b/src/share/vm/memory/metaspace.cpp
--- a/src/share/vm/memory/metaspace.cpp
+++ b/src/share/vm/memory/metaspace.cpp
@@ -1410,42 +1410,41 @@ size_t MetaspaceGC::delta_capacity_until
 }
 
 size_t MetaspaceGC::capacity_until_GC() {
   size_t value = (size_t)OrderAccess::load_ptr_acquire(&_capacity_until_GC);
   assert(value >= MetaspaceSize, "Not initialied properly?");
   return value;
 }
 
-size_t MetaspaceGC::inc_capacity_until_GC(size_t v) {
+bool MetaspaceGC::inc_capacity_until_GC(size_t v, size_t* new_cap_until_GC, size_t* old_cap_until_GC) {
   assert_is_size_aligned(v, Metaspace::commit_alignment());
 
   size_t capacity_until_GC = (size_t) _capacity_until_GC;
   size_t new_value = capacity_until_GC + v;
 
   if (new_value < capacity_until_GC) {
-    // the addition wrapped around, set new_value to max value
-    new_value = max_uintx;
+    // the addition wrapped around, set new_value to aligned max value
+    new_value = align_size_down(max_uintx, Metaspace::commit_alignment());
   }
 
-  bool cas_succeeded = false;
-  size_t num_retries = 5; // just to limit the number of CAS attempts
-  for (size_t i = 0; i < num_retries; i++) {
-    intptr_t cmp = (intptr_t) capacity_until_GC;
-    intptr_t swap = (intptr_t) new_value;
-    intptr_t prev = Atomic::cmpxchg_ptr(swap, &_capacity_until_GC, cmp);
-
-    if (prev == cmp) {
-      cas_succeeded = true;
-      break;
-    }
+  intptr_t expected = (intptr_t) capacity_until_GC;
+  intptr_t actual = Atomic::cmpxchg((intptr_t) new_value, &_capacity_until_GC, expected);
+
+  if (expected != actual) {
+    return false;
   }
 
-  // if the CAS did not succeed, just return the current value
-  return cas_succeeded ? new_value : _capacity_until_GC;
+  if (new_cap_until_GC != NULL) {
+    *new_cap_until_GC = new_value;
+  }
+  if (old_cap_until_GC != NULL) {
+    *old_cap_until_GC = capacity_until_GC;
+  }
+  return true;
 }
 
 size_t MetaspaceGC::dec_capacity_until_GC(size_t v) {
   assert_is_size_aligned(v, Metaspace::commit_alignment());
 
   return (size_t)Atomic::add_ptr(-(intptr_t)v, &_capacity_until_GC);
 }
 
@@ -1535,17 +1534,20 @@ void MetaspaceGC::compute_new_size() {
   size_t shrink_bytes = 0;
   if (capacity_until_GC < minimum_desired_capacity) {
     // If we have less capacity below the metaspace HWM, then
     // increment the HWM.
     size_t expand_bytes = minimum_desired_capacity - capacity_until_GC;
     expand_bytes = align_size_up(expand_bytes, Metaspace::commit_alignment());
     // Don't expand unless it's significant
     if (expand_bytes >= MinMetaspaceExpansion) {
-      size_t new_capacity_until_GC = MetaspaceGC::inc_capacity_until_GC(expand_bytes);
+      size_t new_capacity_until_GC = 0;
+      bool succeeded = MetaspaceGC::inc_capacity_until_GC(expand_bytes, &new_capacity_until_GC);
+      assert(succeeded, "Should always succesfully increment HWM when at safepoint");
+
       Metaspace::tracer()->report_gc_threshold(capacity_until_GC,
                                                new_capacity_until_GC,
                                                MetaspaceGCThresholdUpdater::ComputeNewSize);
       if (PrintGCDetails && Verbose) {
         gclog_or_tty->print_cr("    expanding:"
                       "  minimum_desired_capacity: %6.1fKB"
                       "  expand_bytes: %6.1fKB"
                       "  MinMetaspaceExpansion: %6.1fKB"
@@ -3338,29 +3340,38 @@ MetaWord* Metaspace::allocate(size_t wor
     return  vsm()->allocate(word_size);
   }
 }
 
 MetaWord* Metaspace::expand_and_allocate(size_t word_size, MetadataType mdtype) {
   size_t delta_bytes = MetaspaceGC::delta_capacity_until_GC(word_size * BytesPerWord);
   assert(delta_bytes > 0, "Must be");
 
-  size_t after_inc = MetaspaceGC::inc_capacity_until_GC(delta_bytes);
-
-  // capacity_until_GC might be updated concurrently, must calculate previous value.
-  size_t before_inc = after_inc - delta_bytes;
-
-  tracer()->report_gc_threshold(before_inc, after_inc,
-                                MetaspaceGCThresholdUpdater::ExpandAndAllocate);
-  if (PrintGCDetails && Verbose) {
-    gclog_or_tty->print_cr("Increase capacity to GC from " SIZE_FORMAT
-        " to " SIZE_FORMAT, before_inc, after_inc);
+  size_t before_inc = 0;
+  size_t after_inc = 0;
+  MetaWord* res = NULL;
+  bool inc_succeeded = false;
+
+  while (!inc_succeeded && res == NULL) {
+    inc_succeeded = MetaspaceGC::inc_capacity_until_GC(delta_bytes,
+                                                       &after_inc,
+                                                       &before_inc);
+    res = allocate(word_size, mdtype);
   }
 
-  return allocate(word_size, mdtype);
+  if (inc_succeeded) {
+    tracer()->report_gc_threshold(before_inc, after_inc,
+                                  MetaspaceGCThresholdUpdater::ExpandAndAllocate);
+    if (PrintGCDetails && Verbose) {
+      gclog_or_tty->print_cr("Increase capacity to GC from " SIZE_FORMAT
+          " to " SIZE_FORMAT, before_inc, after_inc);
+    }
+  }
+
+  return res;
 }
 
 // Space allocated in the Metaspace.  This may
 // be across several metadata virtual spaces.
 char* Metaspace::bottom() const {
   assert(DumpSharedSpaces, "only useful and valid for dumping shared spaces");
   return (char*)vsm()->current_chunk()->bottom();
 }
diff --git a/src/share/vm/memory/metaspace.hpp b/src/share/vm/memory/metaspace.hpp
--- a/src/share/vm/memory/metaspace.hpp
+++ b/src/share/vm/memory/metaspace.hpp
@@ -402,17 +402,19 @@ class MetaspaceGC : AllStatic {
   void set_shrink_factor(uint v) { _shrink_factor = v; }
 
  public:
 
   static void initialize();
   static void post_initialize();
 
   static size_t capacity_until_GC();
-  static size_t inc_capacity_until_GC(size_t v);
+  static bool inc_capacity_until_GC(size_t v,
+                                    size_t* new_cap_until_GC = NULL,
+                                    size_t* old_cap_until_GC = NULL);
   static size_t dec_capacity_until_GC(size_t v);
 
   static bool should_concurrent_collect() { return _should_concurrent_collect; }
   static void set_should_concurrent_collect(bool v) {
     _should_concurrent_collect = v;
   }
 
   // The amount to increase the high-water-mark (_capacity_until_GC)
diff --git a/src/share/vm/prims/whitebox.cpp b/src/share/vm/prims/whitebox.cpp
--- a/src/share/vm/prims/whitebox.cpp
+++ b/src/share/vm/prims/whitebox.cpp
@@ -821,22 +821,30 @@ WB_ENTRY(void, WB_FreeMetaspace(JNIEnv* 
 WB_END
 
 WB_ENTRY(jlong, WB_IncMetaspaceCapacityUntilGC(JNIEnv* env, jobject wb, jlong size))
   if (size < 0) {
     THROW_MSG_0(vmSymbols::java_lang_IllegalArgumentException(),
         err_msg("WB_IncMetaspaceCapacityUntilGC: size is negative: " JLONG_FORMAT, size));
   }
 
-  if (size > (jlong) ((size_t) -1)) {
+  jlong max_size_t = (jlong) ((size_t) -1);
+  if (size > max_size_t) {
     THROW_MSG_0(vmSymbols::java_lang_IllegalArgumentException(),
         err_msg("WB_IncMetaspaceCapacityUntilGC: size does not fit in size_t: " JLONG_FORMAT, size));
   }
 
-  size_t new_val = MetaspaceGC::inc_capacity_until_GC(align_size_down((size_t) size, Metaspace::commit_alignment()));
+  size_t new_val = 0;
+  size_t aligned_increment = align_size_down((size_t) size, Metaspace::commit_alignment());
+  bool success = MetaspaceGC::inc_capacity_until_GC(aligned_increment, &new_val);
+  if (!success) {
+    THROW_MSG_0(vmSymbols::java_lang_IllegalStateException(),
+                "WB_IncMetaspaceCapacityUntilGC: could not increase capacity until GC "
+                "due to contention with another thread");
+  }
   return (jlong) new_val;
 WB_END
 
 WB_ENTRY(jlong, WB_MetaspaceCapacityUntilGC(JNIEnv* env, jobject wb))
   return (jlong) MetaspaceGC::capacity_until_GC();
 WB_END
 
 //Some convenience methods to deal with objects from java
diff --git a/test/gc/metaspace/TestCapacityUntilGCWrapAround.java b/test/gc/metaspace/TestCapacityUntilGCWrapAround.java
--- a/test/gc/metaspace/TestCapacityUntilGCWrapAround.java
+++ b/test/gc/metaspace/TestCapacityUntilGCWrapAround.java
@@ -45,14 +45,12 @@ public class TestCapacityUntilGCWrapArou
     public static void main(String[] args) {
         if (Platform.is32bit()) {
             WhiteBox wb = WhiteBox.getWhiteBox();
 
             long before = wb.metaspaceCapacityUntilGC();
             long after = wb.incMetaspaceCapacityUntilGC(MAX_UINT);
 
             Asserts.assertGTE(after, before,
-                String.format("Increasing with MAX_UINT should not cause wrap around: %d < %d", after, before));
-            Asserts.assertEQ(after, MAX_UINT,
-                String.format("Increasing with MAX_UINT should set Metaspace::_capacityUntilGC to max_uint, not: %d", after));
+                              "Increasing with MAX_UINT should not cause wrap around: " + after + " < " + before);
         }
     }
 }