| /* |
| * This file is part of the Jikes RVM project (http://jikesrvm.org). |
| * |
| * This file is licensed to You under the Common Public License (CPL); |
| * You may not use this file except in compliance with the License. You |
| * may obtain a copy of the License at |
| * |
| * http://www.opensource.org/licenses/cpl1.0.php |
| * |
| * See the COPYRIGHT.txt file distributed with this work for information |
| * regarding copyright ownership. |
| */ |
| package org.vmmagic.pragma; |
| |
| import java.lang.annotation.Retention; |
| import java.lang.annotation.Target; |
| import java.lang.annotation.RetentionPolicy; |
| import java.lang.annotation.ElementType; |
| import org.vmmagic.Pragma; |
| |
| /** |
| * By default all Java code is interruptible, that is scheduling or garbage |
| * collection may occur at points within the code. Code can be marked as |
| * {@link Unpreemptible} or {@link Uninterruptible}, that instructs the JVM to |
| * avoid garbage collection and thread scheduling. The {@link Uninterruptible} |
| * annotation disallows any operation that may cause garbage collection or |
| * thread scheduling, for example memory allocation. The {@link Unpreemptible} |
| * annotation doesn't disallow operations that can cause garbage collection or |
| * scheduling, but instructs the JVM to avoid inserting such operations during a |
| * block of code. |
| * |
| * In the internals of a VM most code wants to be {@link Uninterruptible}. |
| * However, code involved in scheduling and locking will cause context switches, |
| * and creating exception objects may trigger garbage collection, this code is |
| * therefore {@link Unpreemptible}. |
| * |
| * Any method that is marked as uninterruptible is treated specially by the |
| * machine code compiler: |
| * |
| * (1) the normal thread switch test that would be emitted in the method |
| * prologue is omitted. |
| * |
| * (2) the stack overflow test that would be emitted in the method prologue is |
| * omitted. |
| * |
| * (3) calls to preemptible code causes warnings. |
| * |
| * (4) bytecodes that can cause interruption cause warnings. |
| * |
| * (5) uninterruptible code will be generated assuming no RuntimeExceptions are |
| * raised and without any GC maps (since by definition there can be noGC if |
| * control is not lost). |
| * |
| * This is the inverse of {@link Interruptible}. |
| */ |
| @Retention(RetentionPolicy.RUNTIME) |
| @Target({ElementType.TYPE, ElementType.METHOD}) |
| @Pragma |
| public @interface Uninterruptible { |
| /** |
| * @return Explanation of why code needs to be uninterruptible |
| */ |
| String value() default ""; |
| } |