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7080700: numAppContexts is accessed in non-threadsafe way in sun.awt.AppContext

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Replace a volatile integer with an AtomicInteger for numAppContexts

Reviewed-by: anthony, art, dholmes
This commit is contained in:
Anthony Petrov 2012-04-16 18:36:58 +04:00
parent afa494b2a5
commit 975313d5cc
1 changed files with 14 additions and 14 deletions
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28
jdk/src/share/classes/sun/awt/AppContext.java
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@ -46,6 +46,7 @@ import sun.util.logging.PlatformLogger;
import java.util.concurrent.locks.Condition; import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock; import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock; import java.util.concurrent.locks.ReentrantLock;
import java.util.concurrent.atomic.AtomicInteger;
/** /**
* The AppContext is a table referenced by ThreadGroup which stores * The AppContext is a table referenced by ThreadGroup which stores
@ -194,6 +195,15 @@ public final class AppContext {
return isDisposed; return isDisposed;
} }
/*
* The total number of AppContexts, system-wide. This number is
* incremented at the beginning of the constructor, and decremented
* at the end of dispose(). getAppContext() checks to see if this
* number is 1. If so, it returns the sole AppContext without
* checking Thread.currentThread().
*/
private static final AtomicInteger numAppContexts = new AtomicInteger(0);
static { static {
// On the main Thread, we get the ThreadGroup, make a corresponding // On the main Thread, we get the ThreadGroup, make a corresponding
// AppContext, and instantiate the Java EventQueue. This way, legacy // AppContext, and instantiate the Java EventQueue. This way, legacy
@ -209,21 +219,11 @@ public final class AppContext {
parentThreadGroup = currentThreadGroup.getParent(); parentThreadGroup = currentThreadGroup.getParent();
} }
mainAppContext = new AppContext(currentThreadGroup); mainAppContext = new AppContext(currentThreadGroup);
numAppContexts = 1;
return null; return null;
} }
}); });
} }
/*
* The total number of AppContexts, system-wide. This number is
* incremented at the beginning of the constructor, and decremented
* at the end of dispose(). getAppContext() checks to see if this
* number is 1. If so, it returns the sole AppContext without
* checking Thread.currentThread().
*/
private static volatile int numAppContexts;
/* /*
* The context ClassLoader that was used to create this AppContext. * The context ClassLoader that was used to create this AppContext.
*/ */
@ -243,7 +243,7 @@ public final class AppContext {
* @since 1.2 * @since 1.2
*/ */
AppContext(ThreadGroup threadGroup) { AppContext(ThreadGroup threadGroup) {
numAppContexts++; numAppContexts.incrementAndGet();
this.threadGroup = threadGroup; this.threadGroup = threadGroup;
threadGroup2appContext.put(threadGroup, this); threadGroup2appContext.put(threadGroup, this);
@ -278,7 +278,7 @@ public final class AppContext {
* @since 1.2 * @since 1.2
*/ */
public final static AppContext getAppContext() { public final static AppContext getAppContext() {
if (numAppContexts == 1) // If there's only one system-wide, if (numAppContexts.get() == 1) // If there's only one system-wide,
return mainAppContext; // return the main system AppContext. return mainAppContext; // return the main system AppContext.
AppContext appContext = threadAppContext.get(); AppContext appContext = threadAppContext.get();
@ -513,7 +513,7 @@ public final class AppContext {
this.table.clear(); // Clear out the Hashtable to ease garbage collection this.table.clear(); // Clear out the Hashtable to ease garbage collection
} }
numAppContexts--; numAppContexts.decrementAndGet();
mostRecentKeyValue = null; mostRecentKeyValue = null;
} }
@ -804,7 +804,7 @@ public final class AppContext {
return getAppContext().isDisposed(); return getAppContext().isDisposed();
} }
public boolean isMainAppContext() { public boolean isMainAppContext() {
return (numAppContexts == 1); return (numAppContexts.get() == 1);
} }
}); });
} }