1berry/openjdk
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

8017739: ReentrantReadWriteLock is confused by the Threads with reused IDs

Browse Source 
Reviewed-by: chegar
This commit is contained in:
Doug Lea 2013-06-28 12:10:18 +01:00
parent 27da77ce6b
commit 0eb360620b
1 changed files with 37 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

50
jdk/src/share/classes/java/util/concurrent/locks/ReentrantReadWriteLock.java
View File

@ -45,7 +45,7 @@ import java.util.Collection;
* <ul>
* <li><b>Acquisition order</b>
*
* <p> This class does not impose a reader or writer preference
* <p>This class does not impose a reader or writer preference
* ordering for lock access. However, it does support an optional
* <em>fairness</em> policy.
*
@ -59,7 +59,7 @@ import java.util.Collection;
* <p>
*
* <dt><b><i>Fair mode</i></b>
* <dd> When constructed as fair, threads contend for entry using an
* <dd>When constructed as fair, threads contend for entry using an
* approximately arrival-order policy. When the currently held lock
* is released, either the longest-waiting single writer thread will
* be assigned the write lock, or if there is a group of reader threads
@ -277,7 +277,7 @@ public class ReentrantReadWriteLock
static final class HoldCounter {
int count = 0;
// Use id, not reference, to avoid garbage retention
final long tid = Thread.currentThread().getId();
final long tid = getThreadId(Thread.currentThread());
}
/**
@ -420,7 +420,7 @@ public class ReentrantReadWriteLock
firstReaderHoldCount--;
} else {
HoldCounter rh = cachedHoldCounter;
if (rh == null || rh.tid != current.getId())
if (rh == null || rh.tid != getThreadId(current))
rh = readHolds.get();
int count = rh.count;
if (count <= 1) {
@ -478,7 +478,7 @@ public class ReentrantReadWriteLock
firstReaderHoldCount++;
} else {
HoldCounter rh = cachedHoldCounter;
if (rh == null || rh.tid != current.getId())
if (rh == null || rh.tid != getThreadId(current))
cachedHoldCounter = rh = readHolds.get();
else if (rh.count == 0)
readHolds.set(rh);
@ -515,7 +515,7 @@ public class ReentrantReadWriteLock
} else {
if (rh == null) {
rh = cachedHoldCounter;
if (rh == null || rh.tid != current.getId()) {
if (rh == null || rh.tid != getThreadId(current)) {
rh = readHolds.get();
if (rh.count == 0)
readHolds.remove();
@ -536,7 +536,7 @@ public class ReentrantReadWriteLock
} else {
if (rh == null)
rh = cachedHoldCounter;
if (rh == null || rh.tid != current.getId())
if (rh == null || rh.tid != getThreadId(current))
rh = readHolds.get();
else if (rh.count == 0)
readHolds.set(rh);
@ -592,7 +592,7 @@ public class ReentrantReadWriteLock
firstReaderHoldCount++;
} else {
HoldCounter rh = cachedHoldCounter;
if (rh == null || rh.tid != current.getId())
if (rh == null || rh.tid != getThreadId(current))
cachedHoldCounter = rh = readHolds.get();
else if (rh.count == 0)
readHolds.set(rh);
@ -643,7 +643,7 @@ public class ReentrantReadWriteLock
return firstReaderHoldCount;
HoldCounter rh = cachedHoldCounter;
if (rh != null && rh.tid == current.getId())
if (rh != null && rh.tid == getThreadId(current))
return rh.count;
int count = readHolds.get().count;
@ -875,7 +875,7 @@ public class ReentrantReadWriteLock
/**
* Attempts to release this lock.
*
* <p> If the number of readers is now zero then the lock
* <p>If the number of readers is now zero then the lock
* is made available for write lock attempts.
*/
public void unlock() {
@ -1017,7 +1017,7 @@ public class ReentrantReadWriteLock
* #tryLock(long, TimeUnit) tryLock(0, TimeUnit.SECONDS) }
* which is almost equivalent (it also detects interruption).
*
* <p> If the current thread already holds this lock then the
* <p>If the current thread already holds this lock then the
* hold count is incremented by one and the method returns
* {@code true}.
*
@ -1126,7 +1126,7 @@ public class ReentrantReadWriteLock
* IllegalMonitorStateException} is thrown.
*
* @throws IllegalMonitorStateException if the current thread does not
* hold this lock.
* hold this lock
*/
public void unlock() {
sync.release(1);
@ -1254,7 +1254,7 @@ public class ReentrantReadWriteLock
* Queries the number of read locks held for this lock. This
* method is designed for use in monitoring system state, not for
* synchronization control.
* @return the number of read locks held.
* @return the number of read locks held
*/
public int getReadLockCount() {
return sync.getReadLockCount();
@ -1484,4 +1484,28 @@ public class ReentrantReadWriteLock
"[Write locks = " + w + ", Read locks = " + r + "]";
}
/**
* Returns the thread id for the given thread. We must access
* this directly rather than via method Thread.getId() because
* getId() is not final, and has been known to be overridden in
* ways that do not preserve unique mappings.
*/
static final long getThreadId(Thread thread) {
return UNSAFE.getLongVolatile(thread, TID_OFFSET);
}
// Unsafe mechanics
private static final sun.misc.Unsafe UNSAFE;
private static final long TID_OFFSET;
static {
try {
UNSAFE = sun.misc.Unsafe.getUnsafe();
Class<?> tk = Thread.class;
TID_OFFSET = UNSAFE.objectFieldOffset
(tk.getDeclaredField("tid"));
} catch (Exception e) {
throw new Error(e);
}
}
}