Make hasUnsafe() return true only when all necessary low level operations are available for reliable direct buffer access

buffer/src/main/java/io/netty/buffer/PoolArena.java

@@ -354,7 +354,7 @@ abstract class PoolArena<T> {
 
     static final class DirectArena extends PoolArena<ByteBuffer> {
 
-        private static final boolean USE_UNSAFE_DIRECTBUF = PlatformDependent.unsafeHasCopyMethods();
+        private static final boolean HAS_UNSAFE = PlatformDependent.hasUnsafe();
 
         DirectArena(PooledByteBufAllocator parent, int pageSize, int maxOrder, int pageShifts, int chunkSize) {
             super(parent, pageSize, maxOrder, pageShifts, chunkSize);
@@ -378,7 +378,7 @@ abstract class PoolArena<T> {
 
         @Override
         protected PooledByteBuf<ByteBuffer> newByteBuf(int maxCapacity) {
-            if (USE_UNSAFE_DIRECTBUF) {
+            if (HAS_UNSAFE) {
                 return new PooledUnsafeDirectByteBuf(maxCapacity);
             } else {
                 return new PooledDirectByteBuf(maxCapacity);
@@ -391,7 +391,7 @@ abstract class PoolArena<T> {
                 return;
             }
 
-            if (USE_UNSAFE_DIRECTBUF) {
+            if (HAS_UNSAFE) {
                 PlatformDependent.copyMemory(
                         PlatformDependent.directBufferAddress(src) + srcOffset,
                         PlatformDependent.directBufferAddress(dst) + dstOffset, length);

buffer/src/main/java/io/netty/buffer/UnpooledByteBufAllocator.java

@@ -41,10 +41,9 @@ public final class UnpooledByteBufAllocator extends AbstractByteBufAllocator {
 
     @Override
     public ByteBuf ioBuffer() {
-        if (PlatformDependent.canFreeDirectBuffer()) {
+        if (PlatformDependent.hasUnsafe()) {
             return directBuffer(0);
         }
-
         return heapBuffer(0);
     }
 }

common/src/main/java/io/netty/util/internal/PlatformDependent.java

@@ -39,8 +39,6 @@ import java.util.regex.Pattern;
  */
 public final class PlatformDependent {
 
-    private static final ClassLoader LOADER = ClassLoader.getSystemClassLoader();
-
     private static final boolean IS_ANDROID = isAndroid0();
     private static final boolean IS_WINDOWS = isWindows0();
     private static final boolean IS_ROOT = isRoot0();
@@ -51,8 +49,6 @@ public final class PlatformDependent {
 
     private static final boolean HAS_UNSAFE = hasUnsafe0();
     private static final boolean CAN_USE_CHM_V8 = HAS_UNSAFE && JAVA_VERSION < 8;
-    private static final boolean CAN_FREE_DIRECT_BUFFER = canFreeDirectBuffer0();
-    private static final boolean UNSAFE_HASE_COPY_METHODS = unsafeHasCopyMethods0();
     private static final long ARRAY_BASE_OFFSET = arrayBaseOffset0();
 
     private static final boolean HAS_JAVASSIST = hasJavassist0();
@@ -94,27 +90,13 @@ public final class PlatformDependent {
     }
 
     /**
-     * Return {@code true} if {@code sun.misc.Unsafe} was found on the classpath and can be used.
+     * Return {@code true} if {@code sun.misc.Unsafe} was found on the classpath and can be used for acclerated
+     * direct memory access.
      */
     public static boolean hasUnsafe() {
         return HAS_UNSAFE;
     }
 
-    /**
-     * Return {@code true} if direct buffers can be freed using an optimized way and so memory footprint will be very
-     * small.
-     */
-    public static boolean canFreeDirectBuffer() {
-        return CAN_FREE_DIRECT_BUFFER;
-    }
-
-    /**
-     * Returns {@code true} if unsafe has all needed copy methods which is not the case on latest openjdk6 atm.
-     */
-    public static boolean unsafeHasCopyMethods() {
-        return UNSAFE_HASE_COPY_METHODS;
-    }
-
     /**
      * Returns {@code true} if and only if Javassist is available.
      */
@@ -178,8 +160,11 @@ public final class PlatformDependent {
         }
     }
 
-    public static long directBufferAddress(ByteBuffer buffer) {
+    /**
-        return PlatformDependent0.directBufferAddress(buffer);
+     * Try to allocate a new direct {@link ByteBuffer} using the best available allocator.
+     */
+    public static ByteBuffer newDirectBuffer(int capacity) {
+        return PlatformDependent0.newDirectBuffer(capacity);
     }
 
     /**
@@ -187,11 +172,15 @@ public final class PlatformDependent {
      * the current platform does not support this operation or the specified buffer is not a direct buffer.
      */
     public static void freeDirectBuffer(ByteBuffer buffer) {
-        if (canFreeDirectBuffer() && buffer.isDirect()) {
+        if (buffer.isDirect()) {
             PlatformDependent0.freeDirectBuffer(buffer);
         }
     }
 
+    public static long directBufferAddress(ByteBuffer buffer) {
+        return PlatformDependent0.directBufferAddress(buffer);
+    }
+
     public static Object getObject(Object object, long fieldOffset) {
         return PlatformDependent0.getObject(object, fieldOffset);
     }
@@ -247,7 +236,7 @@ public final class PlatformDependent {
     private static boolean isAndroid0() {
         boolean android;
         try {
-            Class.forName("android.app.Application", false, LOADER);
+            Class.forName("android.app.Application", false, ClassLoader.getSystemClassLoader());
             android = true;
         } catch (Exception e) {
             android = false;
@@ -341,24 +330,13 @@ public final class PlatformDependent {
             return false;
         }
 
+        try {
             return PlatformDependent0.hasUnsafe();
-    }
+        } catch (Throwable t) {
-
-    private static boolean canFreeDirectBuffer0() {
-        if (isAndroid()) {
             return false;
         }
-
-        return PlatformDependent0.canFreeDirectBuffer();
     }
 
-    private static boolean unsafeHasCopyMethods0() {
-        if (!hasUnsafe()) {
-            return false;
-        }
-
-        return PlatformDependent0.hasCopyMethods();
-    }
     private static long arrayBaseOffset0() {
         if (!hasUnsafe()) {
             return -1;

common/src/main/java/io/netty/util/internal/PlatformDependent0.java

@@ -31,31 +31,15 @@ final class PlatformDependent0 {
     private static final Unsafe UNSAFE;
     private static final long CLEANER_FIELD_OFFSET;
     private static final long ADDRESS_FIELD_OFFSET;
+
     /**
      * {@code true} if and only if the platform supports unaligned access.
      *
      * @see <a href="http://en.wikipedia.org/wiki/Segmentation_fault#Bus_error">Wikipedia on segfault</a>
      */
     private static final boolean UNALIGNED;
-    private static final boolean HAS_COPY_METHODS;
 
     static {
-        Unsafe unsafe;
-        try {
-            Field singleoneInstanceField = Unsafe.class.getDeclaredField("theUnsafe");
-            singleoneInstanceField.setAccessible(true);
-            unsafe = (Unsafe) singleoneInstanceField.get(null);
-        } catch (Throwable cause) {
-            unsafe = null;
-        }
-        UNSAFE = unsafe;
-
-        if (unsafe == null) {
-            CLEANER_FIELD_OFFSET = -1;
-            ADDRESS_FIELD_OFFSET = -1;
-            UNALIGNED = false;
-            HAS_COPY_METHODS = false;
-        } else {
         ByteBuffer direct = ByteBuffer.allocateDirect(1);
         Field cleanerField;
         try {
@@ -66,7 +50,54 @@ final class PlatformDependent0 {
         } catch (Throwable t) {
             cleanerField = null;
         }
-            CLEANER_FIELD_OFFSET = cleanerField != null? objectFieldOffset(cleanerField) : -1;
+
+        Field addressField;
+        try {
+            addressField = Buffer.class.getDeclaredField("address");
+            addressField.setAccessible(true);
+            if (addressField.getLong(ByteBuffer.allocate(1)) != 0) {
+                addressField = null;
+            } else {
+                direct = ByteBuffer.allocateDirect(1);
+                if (addressField.getLong(direct) == 0) {
+                    addressField = null;
+                }
+                Cleaner cleaner = (Cleaner) cleanerField.get(direct);
+                cleaner.clean();
+            }
+        } catch (Throwable t) {
+            addressField = null;
+        }
+
+        Unsafe unsafe;
+        if (addressField != null && cleanerField != null) {
+            try {
+                Field unsafeField = Unsafe.class.getDeclaredField("theUnsafe");
+                unsafeField.setAccessible(true);
+                unsafe = (Unsafe) unsafeField.get(null);
+
+                // Ensure the unsafe supports all necessary methods to work around the mistake in the latest OpenJDK.
+                // https://github.com/netty/netty/issues/1061
+                // http://www.mail-archive.com/jdk6-dev@openjdk.java.net/msg00698.html
+                unsafe.getClass().getDeclaredMethod(
+                        "copyMemory", new Class[] { Object.class, long.class, Object.class, long.class, long.class });
+            } catch (Throwable cause) {
+                unsafe = null;
+            }
+        } else {
+            // If we cannot access the address of a direct buffer, there's no point of using unsafe.
+            // Let's just pretend unsafe is unavailable for overall simplicity.
+            unsafe = null;
+        }
+        UNSAFE = unsafe;
+
+        if (unsafe == null) {
+            CLEANER_FIELD_OFFSET = -1;
+            ADDRESS_FIELD_OFFSET = -1;
+            UNALIGNED = false;
+        } else {
+            ADDRESS_FIELD_OFFSET = objectFieldOffset(addressField);
+            CLEANER_FIELD_OFFSET = objectFieldOffset(cleanerField);
 
             boolean unaligned;
             try {
@@ -75,44 +106,12 @@ final class PlatformDependent0 {
                 unalignedMethod.setAccessible(true);
                 unaligned = Boolean.TRUE.equals(unalignedMethod.invoke(null));
             } catch (Throwable t) {
-                unaligned = false;
+                // We at least know x86 and x64 support unaligned access.
+                String arch = SystemPropertyUtil.get("os.arch", "");
+                //noinspection DynamicRegexReplaceableByCompiledPattern
+                unaligned = arch.matches("^(i[3-6]86|x86(_64)?|x64|amd64)$");
             }
-
-            if (unaligned) {
-                Field addressField = null;
-                try {
-                    addressField = Buffer.class.getDeclaredField("address");
-                    addressField.setAccessible(true);
-                    if (addressField.getLong(ByteBuffer.allocate(1)) != 0) {
-                        unaligned = false;
-                    } else {
-                        ByteBuffer directBuf = ByteBuffer.allocateDirect(1);
-                        if (addressField.getLong(directBuf) == 0) {
-                            unaligned = false;
-                        }
-                        freeDirectBuffer(directBuf);
-                    }
-                } catch (Throwable t) {
-                    unaligned = false;
-                }
-                ADDRESS_FIELD_OFFSET = addressField != null? objectFieldOffset(addressField) : -1;
-            } else {
-                ADDRESS_FIELD_OFFSET = -1;
-            }
-
             UNALIGNED = unaligned;
-            boolean hasCopyMethods;
-            try {
-                // Unsafe does not shop all copy methods in latest openjdk update..
-                // https://github.com/netty/netty/issues/1061
-                // http://www.mail-archive.com/jdk6-dev@openjdk.java.net/msg00698.html
-                UNSAFE.getClass().getDeclaredMethod("copyMemory",
-                        new Class[] { Object.class, long.class, Object.class, long.class, long.class });
-                hasCopyMethods = true;
-            } catch (Throwable ignore) {
-                hasCopyMethods = false;
-            }
-            HAS_COPY_METHODS = hasCopyMethods;
         }
     }
 
@@ -120,26 +119,30 @@ final class PlatformDependent0 {
         return UNSAFE != null;
     }
 
-    static boolean canFreeDirectBuffer() {
+    static ByteBuffer newDirectBuffer(int capacity) {
-        return ADDRESS_FIELD_OFFSET >= 0;
+        if (hasUnsafe()) {
+            return ByteBuffer.allocateDirect(capacity);
+        } else {
+            throw new Error("refusing to create a direct buffer without proper access to the low-level API");
         }
-
-    static long directBufferAddress(ByteBuffer buffer) {
-        return getLong(buffer, ADDRESS_FIELD_OFFSET);
     }
 
     static void freeDirectBuffer(ByteBuffer buffer) {
         Cleaner cleaner;
         try {
             cleaner = (Cleaner) getObject(buffer, CLEANER_FIELD_OFFSET);
+            if (cleaner == null) {
+                throw new IllegalArgumentException(
+                        "attempted to deallocate the buffer which was allocated via JNIEnv->NewDirectByteBuffer()");
+            }
             cleaner.clean();
         } catch (Throwable t) {
             // Nothing we can do here.
         }
     }
 
-    static boolean hasCopyMethods() {
+    static long directBufferAddress(ByteBuffer buffer) {
-        return HAS_COPY_METHODS;
+        return getLong(buffer, ADDRESS_FIELD_OFFSET);
     }
 
     static long arrayBaseOffset() {