/* * Copyright (C) 2016 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ import java.lang.reflect.Field; import java.util.concurrent.atomic.AtomicBoolean; import sun.misc.Unsafe; /** * Checker test on the 1.8 unsafe operations. Note, this is by no means an * exhaustive unit test for these CAS (compare-and-swap) and fence operations. * Instead, this test ensures the methods are recognized as intrinsic and behave * as expected. */ public class Main { private static final Unsafe unsafe = getUnsafe(); private static Thread[] sThreads = new Thread[10]; // // Fields accessed by setters and adders, and by memory fence tests. // public int i = 0; public long l = 0; public Object o = null; public int x_value; public int y_value; public volatile boolean running; // // Setters. // /// CHECK-START: int Main.set32(java.lang.Object, long, int) builder (after) /// CHECK-DAG: <<Result:i\d+>> InvokeVirtual intrinsic:UnsafeGetAndSetInt /// CHECK-DAG: Return [<<Result>>] private static int set32(Object o, long offset, int newValue) { return unsafe.getAndSetInt(o, offset, newValue); } /// CHECK-START: long Main.set64(java.lang.Object, long, long) builder (after) /// CHECK-DAG: <<Result:j\d+>> InvokeVirtual intrinsic:UnsafeGetAndSetLong /// CHECK-DAG: Return [<<Result>>] private static long set64(Object o, long offset, long newValue) { return unsafe.getAndSetLong(o, offset, newValue); } /// CHECK-START: java.lang.Object Main.setObj(java.lang.Object, long, java.lang.Object) builder (after) /// CHECK-DAG: <<Result:l\d+>> InvokeVirtual intrinsic:UnsafeGetAndSetObject /// CHECK-DAG: Return [<<Result>>] private static Object setObj(Object o, long offset, Object newValue) { return unsafe.getAndSetObject(o, offset, newValue); } // // Adders. // /// CHECK-START: int Main.add32(java.lang.Object, long, int) builder (after) /// CHECK-DAG: <<Result:i\d+>> InvokeVirtual intrinsic:UnsafeGetAndAddInt /// CHECK-DAG: Return [<<Result>>] private static int add32(Object o, long offset, int delta) { return unsafe.getAndAddInt(o, offset, delta); } /// CHECK-START: long Main.add64(java.lang.Object, long, long) builder (after) /// CHECK-DAG: <<Result:j\d+>> InvokeVirtual intrinsic:UnsafeGetAndAddLong /// CHECK-DAG: Return [<<Result>>] private static long add64(Object o, long offset, long delta) { return unsafe.getAndAddLong(o, offset, delta); } // // Fences (native). // /// CHECK-START: void Main.load() builder (after) /// CHECK-DAG: InvokeVirtual intrinsic:UnsafeLoadFence // /// CHECK-START: void Main.load() instruction_simplifier (after) /// CHECK-NOT: InvokeVirtual intrinsic:UnsafeLoadFence // /// CHECK-START: void Main.load() instruction_simplifier (after) /// CHECK-DAG: MemoryBarrier kind:LoadAny private static void load() { unsafe.loadFence(); } /// CHECK-START: void Main.store() builder (after) /// CHECK-DAG: InvokeVirtual intrinsic:UnsafeStoreFence // /// CHECK-START: void Main.store() instruction_simplifier (after) /// CHECK-NOT: InvokeVirtual intrinsic:UnsafeStoreFence // /// CHECK-START: void Main.store() instruction_simplifier (after) /// CHECK-DAG: MemoryBarrier kind:AnyStore private static void store() { unsafe.storeFence(); } /// CHECK-START: void Main.full() builder (after) /// CHECK-DAG: InvokeVirtual intrinsic:UnsafeFullFence // /// CHECK-START: void Main.full() instruction_simplifier (after) /// CHECK-NOT: InvokeVirtual intrinsic:UnsafeFullFence // /// CHECK-START: void Main.full() instruction_simplifier (after) /// CHECK-DAG: MemoryBarrier kind:AnyAny private static void full() { unsafe.fullFence(); } // // Thread fork/join. // private static void fork(Runnable r) { for (int i = 0; i < 10; i++) { sThreads[i] = new Thread(r); } // Start the threads only after the full array has been written with new threads, // because one test relies on the contents of this array to be consistent. for (int i = 0; i < 10; i++) { sThreads[i].start(); } } private static void join() { try { for (int i = 0; i < 10; i++) { sThreads[i].join(); } } catch (InterruptedException e) { throw new Error("Failed join: " + e); } } // // Driver. // public static void main(String[] args) { System.out.println("starting"); final Main m = new Main(); // Get the offsets. final long intOffset, longOffset, objOffset; try { Field intField = Main.class.getDeclaredField("i"); Field longField = Main.class.getDeclaredField("l"); Field objField = Main.class.getDeclaredField("o"); intOffset = unsafe.objectFieldOffset(intField); longOffset = unsafe.objectFieldOffset(longField); objOffset = unsafe.objectFieldOffset(objField); } catch (NoSuchFieldException e) { throw new Error("No offset: " + e); } // Some sanity on setters and adders within same thread. set32(m, intOffset, 3); expectEqual32(3, m.i); set64(m, longOffset, 7L); expectEqual64(7L, m.l); setObj(m, objOffset, m); expectEqualObj(m, m.o); add32(m, intOffset, 11); expectEqual32(14, m.i); add64(m, longOffset, 13L); expectEqual64(20L, m.l); // Some sanity on setters within different threads. fork(new Runnable() { public void run() { for (int i = 0; i < 10; i++) set32(m, intOffset, i); } }); join(); expectEqual32(9, m.i); // one thread's last value wins fork(new Runnable() { public void run() { for (int i = 0; i < 10; i++) set64(m, longOffset, (long) (100 + i)); } }); join(); expectEqual64(109L, m.l); // one thread's last value wins fork(new Runnable() { public void run() { for (int i = 0; i < 10; i++) setObj(m, objOffset, sThreads[i]); } }); join(); expectEqualObj(sThreads[9], m.o); // one thread's last value wins // Some sanity on adders within different threads. fork(new Runnable() { public void run() { for (int i = 0; i < 10; i++) add32(m, intOffset, i + 1); } }); join(); expectEqual32(559, m.i); // all values accounted for fork(new Runnable() { public void run() { for (int i = 0; i < 10; i++) add64(m, longOffset, (long) (i + 1)); } }); join(); expectEqual64(659L, m.l); // all values accounted for // Some sanity on fences within same thread. Note that memory fences within one // thread make little sense, but the sanity check ensures nothing bad happens. m.i = -1; m.l = -2L; m.o = null; load(); store(); full(); expectEqual32(-1, m.i); expectEqual64(-2L, m.l); expectEqualObj(null, m.o); // Some sanity on full fence within different threads. We write the non-volatile m.l after // the fork(), which means there is no happens-before relation in the Java memory model // with respect to the read in the threads. This relation is enforced by the memory fences // and the weak-set() -> get() guard. Note that the guard semantics used here are actually // too strong and already enforce total memory visibility, but this test illustrates what // should still happen if Java had a true relaxed memory guard. final AtomicBoolean guard1 = new AtomicBoolean(); m.l = 0L; fork(new Runnable() { public void run() { while (!guard1.get()); // busy-waiting full(); expectEqual64(-123456789L, m.l); } }); m.l = -123456789L; full(); while (!guard1.weakCompareAndSet(false, true)); // relaxed memory order join(); // Some sanity on release/acquire fences within different threads. We write the non-volatile // m.l after the fork(), which means there is no happens-before relation in the Java memory // model with respect to the read in the threads. This relation is enforced by the memory fences // and the weak-set() -> get() guard. Note that the guard semantics used here are actually // too strong and already enforce total memory visibility, but this test illustrates what // should still happen if Java had a true relaxed memory guard. final AtomicBoolean guard2 = new AtomicBoolean(); m.l = 0L; fork(new Runnable() { public void run() { while (!guard2.get()); // busy-waiting load(); expectEqual64(-987654321L, m.l); } }); m.l = -987654321L; store(); while (!guard2.weakCompareAndSet(false, true)); // relaxed memory order join(); // Some sanity on release/acquire fences within different threads using a test suggested by // Hans Boehm. Even this test remains with the realm of sanity only, since having the threads // read the same value consistently would be a valid outcome. m.x_value = -1; m.y_value = -1; m.running = true; fork(new Runnable() { public void run() { while (m.running) { for (int few_times = 0; few_times < 1000; few_times++) { // Read y first, then load fence, then read x. // They should appear in order, if seen at all. int local_y = m.y_value; load(); int local_x = m.x_value; expectLessThanOrEqual32(local_y, local_x); } } } }); for (int many_times = 0; many_times < 100000; many_times++) { m.x_value = many_times; store(); m.y_value = many_times; } m.running = false; join(); // All done! System.out.println("passed"); } // Use reflection to implement "Unsafe.getUnsafe()"; private static Unsafe getUnsafe() { try { Class<?> unsafeClass = Unsafe.class; Field f = unsafeClass.getDeclaredField("theUnsafe"); f.setAccessible(true); return (Unsafe) f.get(null); } catch (Exception e) { throw new Error("Cannot get Unsafe instance"); } } private static void expectEqual32(int expected, int result) { if (expected != result) { throw new Error("Expected: " + expected + ", found: " + result); } } private static void expectLessThanOrEqual32(int val1, int val2) { if (val1 > val2) { throw new Error("Expected: " + val1 + " <= " + val2); } } private static void expectEqual64(long expected, long result) { if (expected != result) { throw new Error("Expected: " + expected + ", found: " + result); } } private static void expectEqualObj(Object expected, Object result) { if (expected != result) { throw new Error("Expected: " + expected + ", found: " + result); } } }