Summary

Deprecate for removal the sun.misc.Unsafe park, unpark, getLoadAverage, loadFence, storeFence, and fullFence methods. These methods have standard API equivalents for many years and releases.

Problem

sun.misc.Unsafe is an undocumented/unsupported critical internal API. We need to encourage libraries that use this API directly to move to using standard APIs where possible.

Solution

Deprecate the 6 methods for removal. The @deprecation text will link to the standard APIs to use.

Add a release note.

Specification

+++ b/src/jdk.unsupported/share/classes/sun/misc/Unsafe.java
@@ -1089,7 +1089,10 @@ public void putOrderedLong(Object o, long offset, long x) {
      * so when calling from native code.
      *
      * @param thread the thread to unpark.
+     *
+     * @deprecated Use {@link java.util.concurrent.locks.LockSupport#unpark(Thread)} instead.
      */
+    @Deprecated(since="22", forRemoval=true)
     @ForceInline
     public void unpark(Object thread) {
         theInternalUnsafe.unpark(thread);
@@ -1105,7 +1108,11 @@ public void unpark(Object thread) {
      * "reason"). Note: This operation is in the Unsafe class only
      * because {@code unpark} is, so it would be strange to place it
      * elsewhere.
+     *
+     * @deprecated Use {@link java.util.concurrent.locks.LockSupport#parkNanos(long)} or
+     * {@link java.util.concurrent.locks.LockSupport#parkUntil(long)} instead.
      */
+    @Deprecated(since="22", forRemoval=true)
     @ForceInline
     public void park(boolean isAbsolute, long time) {
         theInternalUnsafe.park(isAbsolute, time);
@@ -1125,7 +1132,11 @@ public void park(boolean isAbsolute, long time) {
      *
      * @return the number of samples actually retrieved; or -1
      *         if the load average is unobtainable.
+     *
+     * @deprecated Use {@link java.lang.management.OperatingSystemMXBean#getSystemLoadAverage()}
+     * instead.
      */
+    @Deprecated(since="22", forRemoval=true)
     @ForceInline
     public int getLoadAverage(double[] loadavg, int nelems) {
         return theInternalUnsafe.getLoadAverage(loadavg, nelems);
@@ -1225,8 +1235,11 @@ public final Object getAndSetObject(Object o, long offset, Object newValue) {
      * A pure LoadLoad fence is not provided, since the addition of LoadStore
      * is almost always desired, and most current hardware instructions that
      * provide a LoadLoad barrier also provide a LoadStore barrier for free.
+     *
+     * @deprecated Use {@link java.lang.invoke.VarHandle#acquireFence()} instead.
      * @since 1.8
      */
+    @Deprecated(since="22", forRemoval=true)
     @ForceInline
     public void loadFence() {
         theInternalUnsafe.loadFence();
@@ -1242,8 +1255,11 @@ public void loadFence() {
      * A pure StoreStore fence is not provided, since the addition of LoadStore
      * is almost always desired, and most current hardware instructions that
      * provide a StoreStore barrier also provide a LoadStore barrier for free.
+     *
+     * @deprecated Use {@link java.lang.invoke.VarHandle#releaseFence()} instead.
      * @since 1.8
      */
+    @Deprecated(since="22", forRemoval=true)
     @ForceInline
     public void storeFence() {
         theInternalUnsafe.storeFence();
@@ -1256,8 +1272,11 @@ public void storeFence() {
      * barrier.
      *
      * Corresponds to C11 atomic_thread_fence(memory_order_seq_cst).
+     *
+     * @deprecated Use {@link java.lang.invoke.VarHandle#fullFence()} instead.
      * @since 1.8
      */
+    @Deprecated(since="22", forRemoval=true)
     @ForceInline
     public void fullFence() {
         theInternalUnsafe.fullFence();