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提交 a71a0e3d authored 作者: Andrei Tokar's avatar Andrei Tokar
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replace synchronized(this) in MVStore with ReentrantLock

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h2/src/main/org/h2/mvstore/MVStore.java
浏览文件 @ a71a0e3d
......@@ -25,7 +25,7 @@ import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicLong;
import java.util.concurrent.atomic.AtomicReference;
import java.util.concurrent.locks.ReentrantLock;
import org.h2.compress.CompressDeflate;
import org.h2.compress.CompressLZF;
import org.h2.compress.Compressor;
......@@ -144,6 +144,14 @@ public class MVStore {
*/
private static final int MARKED_FREE = 10_000_000;
/**
* Lock which governs access to major store operations: store(), close(), ...
* It should used in a non-reentrant fashion.
* It serves as a replacement for synchronized(this), except it allows for
* non-blocking lock attempts.
*/
private final ReentrantLock storeLock = new ReentrantLock();
/**
* The background thread, if any.
*/
......@@ -195,8 +203,7 @@ public class MVStore {
private final Map<Integer, Chunk> freedPageSpace = new HashMap<>();
/**
* The metadata map. Write access to this map needs to be synchronized on
* the store.
* The metadata map. Write access to this map needs to be done under storeLock.
*/
private final MVMap<String, String> meta;
......@@ -274,12 +281,6 @@ public class MVStore {
*/
private volatile long currentStoreVersion = -1;
/**
* Holds reference to a thread performing store operation (if any)
* or null if there is none is in progress.
*/
private final AtomicReference<Thread> currentStoreThread = new AtomicReference<>();
private volatile boolean metaChanged;
/**
......@@ -289,7 +290,9 @@ public class MVStore {
private final int autoCompactFillRate;
private long autoCompactLastFileOpCount;
/**
* Simple lock to ensure that no more than one compaction runs at any given time
*/
private final Object compactSync = new Object();
private volatile IllegalStateException panicException;
......@@ -474,8 +477,9 @@ public class MVStore {
* @param builder the map builder
* @return the map
*/
public synchronized <M extends MVMap<K, V>, K, V> M openMap(
String name, MVMap.MapBuilder<M, K, V> builder) {
public <M extends MVMap<K, V>, K, V> M openMap(String name, MVMap.MapBuilder<M, K, V> builder) {
storeLock.lock();
try {
int id = getMapId(name);
M map;
if (id >= 0) {
......@@ -493,16 +497,20 @@ public class MVStore {
map.setRootPos(0, lastStoredVersion);
markMetaChanged();
@SuppressWarnings("unchecked")
M existingMap = (M)maps.putIfAbsent(id, map);
if(existingMap != null) {
M existingMap = (M) maps.putIfAbsent(id, map);
if (existingMap != null) {
map = existingMap;
}
}
return map;
} finally {
storeLock.unlock();
}
}
public synchronized <M extends MVMap<K, V>, K, V> M openMap(int id,
MVMap.MapBuilder<M, K, V> builder) {
public <M extends MVMap<K, V>, K, V> M openMap(int id, MVMap.MapBuilder<M, K, V> builder) {
storeLock.lock();
try {
@SuppressWarnings("unchecked")
M map = (M) getMap(id);
if (map == null) {
......@@ -519,6 +527,9 @@ public class MVStore {
}
}
return map;
} finally {
storeLock.unlock();
}
}
public <K, V> MVMap<K,V> getMap(int id) {
......@@ -954,12 +965,10 @@ public class MVStore {
if (closed) {
return;
}
// can not synchronize on this yet, because
// the thread also synchronized on this, which
// could result in a deadlock
stopBackgroundThread();
closed = true;
synchronized (this) {
storeLock.lock();
try {
if (fileStore != null && shrinkIfPossible) {
shrinkFileIfPossible(0);
}
......@@ -979,6 +988,8 @@ public class MVStore {
if (fileStore != null && !fileStoreIsProvided) {
fileStore.close();
}
} finally {
storeLock.unlock();
}
}
......@@ -1043,11 +1054,15 @@ public class MVStore {
* @return the new version (incremented if there were changes)
*/
public long tryCommit() {
// unlike synchronization, this will also prevent re-entrance,
// which may be possible, if the meta map have changed
if (currentStoreThread.compareAndSet(null, Thread.currentThread())) {
synchronized (this) {
// we need to prevent re-entrance, which may be possible,
// because meta map is modified within storeNow() and that
// causes beforeWrite() call with possibility of going back here
if ((!storeLock.isHeldByCurrentThread() || currentStoreVersion < 0) &&
storeLock.tryLock()) {
try {
store();
} finally {
storeLock.unlock();
}
}
return currentVersion;
......@@ -1069,15 +1084,16 @@ public class MVStore {
*
* @return the new version (incremented if there were changes)
*/
public synchronized long commit() {
Thread currentThread = Thread.currentThread();
Thread storeThread = currentStoreThread.get();
if (currentThread != storeThread) { // to avoid re-entrance
currentStoreThread.set(currentThread);
public long commit() {
// we need to prevent re-entrance, which may be possible,
// because meta map is modified within storeNow() and that
// causes beforeWrite() call with possibility of going back here
if(!storeLock.isHeldByCurrentThread() || currentStoreVersion < 0) {
storeLock.lock();
try {
store();
} finally {
currentStoreThread.set(storeThread);
storeLock.unlock();
}
}
return currentVersion;
......@@ -1111,12 +1127,11 @@ public class MVStore {
// in any case reset the current store version,
// to allow closing the store
currentStoreVersion = -1;
currentStoreThread.set(null);
}
}
private void storeNow() {
assert Thread.holdsLock(this);
assert storeLock.isHeldByCurrentThread();
long time = getTimeSinceCreation();
freeUnusedIfNeeded(time);
int currentUnsavedPageCount = unsavedMemory;
......@@ -1322,7 +1337,8 @@ public class MVStore {
}
}
private synchronized void freeUnusedChunks() {
private void freeUnusedChunks() {
assert storeLock.isHeldByCurrentThread();
if (lastChunk != null && reuseSpace) {
Set<Integer> referenced = collectReferencedChunks();
long time = getTimeSinceCreation();
......@@ -1693,7 +1709,9 @@ public class MVStore {
*
* @return if anything was written
*/
public synchronized boolean compactRewriteFully() {
public boolean compactRewriteFully() {
storeLock.lock();
try {
checkOpen();
if (lastChunk == null) {
// nothing to do
......@@ -1718,6 +1736,10 @@ public class MVStore {
}
commit();
return true;
} finally {
storeLock.unlock();
}
}
/**
......@@ -1737,7 +1759,9 @@ public class MVStore {
* than this
* @param moveSize the number of bytes to move
*/
public synchronized void compactMoveChunks(int targetFillRate, long moveSize) {
public void compactMoveChunks(int targetFillRate, long moveSize) {
storeLock.lock();
try {
checkOpen();
if (lastChunk != null && reuseSpace) {
int oldRetentionTime = retentionTime;
......@@ -1755,6 +1779,9 @@ public class MVStore {
retentionTime = oldRetentionTime;
}
}
} finally {
storeLock.unlock();
}
}
private ArrayList<Chunk> findChunksToMove(long startBlock, long moveSize) {
......@@ -1896,16 +1923,24 @@ public class MVStore {
synchronized (compactSync) {
checkOpen();
ArrayList<Chunk> old;
synchronized (this) {
// We can't wait fo lock here, because if called from the background thread,
// it might go into deadlock with concurrent database closure
// and attempt to stop this thread.
if (storeLock.tryLock()) {
try {
old = findOldChunks(targetFillRate, write);
}
if (old == null || old.isEmpty()) {
return false;
}
compactRewrite(old);
return true;
} finally {
storeLock.unlock();
}
}
}
return false;
}
/**
* Get the current fill rate (percentage of used space in the file). Unlike
......@@ -2336,10 +2371,15 @@ public class MVStore {
*
* @param version the new store version
*/
public synchronized void setStoreVersion(int version) {
public void setStoreVersion(int version) {
storeLock.lock();
try {
checkOpen();
markMetaChanged();
meta.put("setting.storeVersion", Integer.toHexString(version));
} finally {
storeLock.unlock();
}
}
/**
......@@ -2358,7 +2398,9 @@ public class MVStore {
*
* @param version the version to revert to
*/
public synchronized void rollbackTo(long version) {
public void rollbackTo(long version) {
storeLock.lock();
try {
checkOpen();
if (version == 0) {
// special case: remove all data
......@@ -2457,6 +2499,9 @@ public class MVStore {
if (lastStoredVersion == INITIAL_VERSION) {
lastStoredVersion = currentVersion - 1;
}
} finally {
storeLock.unlock();
}
}
private static long getRootPos(MVMap<String, String> map, int mapId) {
......@@ -2544,7 +2589,9 @@ public class MVStore {
removeMap(map, true);
}
public synchronized void removeMap(MVMap<?, ?> map, boolean delayed) {
public void removeMap(MVMap<?, ?> map, boolean delayed) {
storeLock.lock();
try {
checkOpen();
DataUtils.checkArgument(map != meta,
"Removing the meta map is not allowed");
......@@ -2556,6 +2603,9 @@ public class MVStore {
int id = map.getId();
String name = getMapName(id);
removeMap(name, id, delayed);
} finally {
storeLock.unlock();
}
}
private void removeMap(String name, int id, boolean delayed) {
......@@ -2681,11 +2731,7 @@ public class MVStore {
synchronized (t.sync) {
t.sync.notifyAll();
}
if (Thread.holdsLock(this)) {
// called from storeNow: can not join,
// because that could result in a deadlock
return;
}
try {
t.join();
} catch (Exception e) {
......@@ -2855,11 +2901,11 @@ public class MVStore {
public void deregisterVersionUsage(TxCounter txCounter) {
if(txCounter != null) {
if(txCounter.counter.decrementAndGet() <= 0) {
if (currentStoreThread.compareAndSet(null, Thread.currentThread())) {
if (!storeLock.isHeldByCurrentThread() && storeLock.tryLock()) {
try {
dropUnusedVersions();
} finally {
currentStoreThread.set(null);
storeLock.unlock();
}
}
}
......
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