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Don't try to put back MemoryRegionCache.Entry objects into the Recycler when recycled because of a finalizer. (#8955) 

Motivation:

In MemoryRegionCache.Entry we use the Recycler to reduce GC pressure and churn. The problem is that these will also be recycled when the PoolThreadCache is collected and finalize() is called. This then can have the effect that we try to load class but the WebApp is already stoped.

This will produce an stacktrace like this on Tomcat:

```
19-Mar-2019 15:53:21.351 INFO [Finalizer] org.apache.catalina.loader.WebappClassLoaderBase.checkStateForResourceLoading Illegal access: this web application instance has been stopped already. Could not load [java.util.WeakHashMap]. The following stack trace is thrown for debugging purposes as well as to attempt to terminate the thread which caused the illegal access.
 java.lang.IllegalStateException: Illegal access: this web application instance has been stopped already. Could not load [java.util.WeakHashMap]. The following stack trace is thrown for debugging purposes as well as to attempt to terminate the thread which caused the illegal access.
	at org.apache.catalina.loader.WebappClassLoaderBase.checkStateForResourceLoading(WebappClassLoaderBase.java:1383)
	at org.apache.catalina.loader.WebappClassLoaderBase.checkStateForClassLoading(WebappClassLoaderBase.java:1371)
	at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1224)
	at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1186)
	at io.netty.util.Recycler$3.initialValue(Recycler.java:233)
	at io.netty.util.Recycler$3.initialValue(Recycler.java:230)
	at io.netty.util.concurrent.FastThreadLocal.initialize(FastThreadLocal.java:188)
	at io.netty.util.concurrent.FastThreadLocal.get(FastThreadLocal.java:142)
	at io.netty.util.Recycler$Stack.pushLater(Recycler.java:624)
	at io.netty.util.Recycler$Stack.push(Recycler.java:597)
	at io.netty.util.Recycler$DefaultHandle.recycle(Recycler.java:225)
	at io.netty.buffer.PoolThreadCache$MemoryRegionCache$Entry.recycle(PoolThreadCache.java:478)
	at io.netty.buffer.PoolThreadCache$MemoryRegionCache.freeEntry(PoolThreadCache.java:459)
	at io.netty.buffer.PoolThreadCache$MemoryRegionCache.free(PoolThreadCache.java:430)
	at io.netty.buffer.PoolThreadCache$MemoryRegionCache.free(PoolThreadCache.java:422)
	at io.netty.buffer.PoolThreadCache.free(PoolThreadCache.java:279)
	at io.netty.buffer.PoolThreadCache.free(PoolThreadCache.java:270)
	at io.netty.buffer.PoolThreadCache.free(PoolThreadCache.java:241)
	at io.netty.buffer.PoolThreadCache.finalize(PoolThreadCache.java:230)
	at java.lang.System$2.invokeFinalize(System.java:1270)
	at java.lang.ref.Finalizer.runFinalizer(Finalizer.java:102)
	at java.lang.ref.Finalizer.access$100(Finalizer.java:34)
	at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:217)
```

Beside this we also need to ensure we not try to lazy load SizeClass when the finalizer is used as it may not be present anymore if the ClassLoader is already destroyed.

This would produce an error like:

```
20-Mar-2019 11:26:35.254 INFO [Finalizer] org.apache.catalina.loader.WebappClassLoaderBase.checkStateForResourceLoading Illegal access: this web application instance has been stopped already. Could not load [io.netty.buffer.PoolArena$1]. The following stack trace is thrown for debugging purposes as well as to attempt to terminate the thread which caused the illegal access.
 java.lang.IllegalStateException: Illegal access: this web application instance has been stopped already. Could not load [io.netty.buffer.PoolArena$1]. The following stack trace is thrown for debugging purposes as well as to attempt to terminate the thread which caused the illegal access.
	at org.apache.catalina.loader.WebappClassLoaderBase.checkStateForResourceLoading(WebappClassLoaderBase.java:1383)
	at org.apache.catalina.loader.WebappClassLoaderBase.checkStateForClassLoading(WebappClassLoaderBase.java:1371)
	at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1224)
	at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1186)
	at io.netty.buffer.PoolArena.freeChunk(PoolArena.java:287)
	at io.netty.buffer.PoolThreadCache$MemoryRegionCache.freeEntry(PoolThreadCache.java:464)
	at io.netty.buffer.PoolThreadCache$MemoryRegionCache.free(PoolThreadCache.java:429)
	at io.netty.buffer.PoolThreadCache$MemoryRegionCache.free(PoolThreadCache.java:421)
	at io.netty.buffer.PoolThreadCache.free(PoolThreadCache.java:278)
	at io.netty.buffer.PoolThreadCache.free(PoolThreadCache.java:269)
	at io.netty.buffer.PoolThreadCache.free(PoolThreadCache.java:240)
	at io.netty.buffer.PoolThreadCache.finalize(PoolThreadCache.java:229)
	at java.lang.System$2.invokeFinalize(System.java:1270)
	at java.lang.ref.Finalizer.runFinalizer(Finalizer.java:102)
	at java.lang.ref.Finalizer.access$100(Finalizer.java:34)
	at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:217)
```

Modifications:

- Only try to put the Entry back into the Recycler if the PoolThredCache is not destroyed because of the finalizer.
- Only try to access SizeClass if not triggered by finalizer.

Result:

No IllegalStateException anymoe when a webapp is reloaded in Tomcat that uses netty and uses the PooledByteBufAllocator.
This commit is contained in:
Norman Maurer 2019-03-22 12:16:21 +01:00 committed by GitHub
parent b36f75044f
commit 922e463524
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
3 changed files with 43 additions and 36 deletions
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32
buffer/src/main/java/io/netty/buffer/PoolArena.java
View File

@ -276,7 +276,7 @@ abstract class PoolArena<T> implements PoolArenaMetric {
return;
}
freeChunk(chunk, handle, sizeClass, nioBuffer);
freeChunk(chunk, handle, sizeClass, nioBuffer, false);
}
}
@ -287,21 +287,25 @@ abstract class PoolArena<T> implements PoolArenaMetric {
return isTiny(normCapacity) ? SizeClass.Tiny : SizeClass.Small;
}
void freeChunk(PoolChunk<T> chunk, long handle, SizeClass sizeClass, ByteBuffer nioBuffer) {
void freeChunk(PoolChunk<T> chunk, long handle, SizeClass sizeClass, ByteBuffer nioBuffer, boolean finalizer) {
final boolean destroyChunk;
synchronized (this) {
switch (sizeClass) {
case Normal:
++deallocationsNormal;
break;
case Small:
++deallocationsSmall;
break;
case Tiny:
++deallocationsTiny;
break;
default:
throw new Error();
// We only call this if freeChunk is not called because of the PoolThreadCache finalizer as otherwise this
// may fail due lazy class-loading in for example tomcat.
if (!finalizer) {
switch (sizeClass) {
case Normal:
++deallocationsNormal;
break;
case Small:
++deallocationsSmall;
break;
case Tiny:
++deallocationsTiny;
break;
default:
throw new Error();
}
}
destroyChunk = !chunk.parent.free(chunk, handle, nioBuffer);
}

45
buffer/src/main/java/io/netty/buffer/PoolThreadCache.java
View File

@ -227,23 +227,23 @@ final class PoolThreadCache {
try {
super.finalize();
} finally {
free();
free(true);
}
}
/**
* Should be called if the Thread that uses this cache is about to exist to release resources out of the cache
*/
void free() {
void free(boolean finalizer) {
// As free() may be called either by the finalizer or by FastThreadLocal.onRemoval(...) we need to ensure
// we only call this one time.
if (freed.compareAndSet(false, true)) {
int numFreed = free(tinySubPageDirectCaches) +
free(smallSubPageDirectCaches) +
free(normalDirectCaches) +
free(tinySubPageHeapCaches) +
free(smallSubPageHeapCaches) +
free(normalHeapCaches);
int numFreed = free(tinySubPageDirectCaches, finalizer) +
free(smallSubPageDirectCaches, finalizer) +
free(normalDirectCaches, finalizer) +
free(tinySubPageHeapCaches, finalizer) +
free(smallSubPageHeapCaches, finalizer) +
free(normalHeapCaches, finalizer);
if (numFreed > 0 && logger.isDebugEnabled()) {
logger.debug("Freed {} thread-local buffer(s) from thread: {}", numFreed,
@ -260,23 +260,23 @@ final class PoolThreadCache {
}
}
private static int free(MemoryRegionCache<?>[] caches) {
private static int free(MemoryRegionCache<?>[] caches, boolean finalizer) {
if (caches == null) {
return 0;
}
int numFreed = 0;
for (MemoryRegionCache<?> c: caches) {
numFreed += free(c);
numFreed += free(c, finalizer);
}
return numFreed;
}
private static int free(MemoryRegionCache<?> cache) {
private static int free(MemoryRegionCache<?> cache, boolean finalizer) {
if (cache == null) {
return 0;
}
return cache.free();
return cache.free(finalizer);
}
void trim() {
@ -418,16 +418,16 @@ final class PoolThreadCache {
/**
* Clear out this cache and free up all previous cached {@link PoolChunk}s and {@code handle}s.
*/
public final int free() {
return free(Integer.MAX_VALUE);
public final int free(boolean finalizer) {
return free(Integer.MAX_VALUE, finalizer);
}
private int free(int max) {
private int free(int max, boolean finalizer) {
int numFreed = 0;
for (; numFreed < max; numFreed++) {
Entry<T> entry = queue.poll();
if (entry != null) {
freeEntry(entry);
freeEntry(entry, finalizer);
} else {
// all cleared
return numFreed;
@ -445,20 +445,23 @@ final class PoolThreadCache {
// We not even allocated all the number that are
if (free > 0) {
free(free);
free(free, false);
}
}
@SuppressWarnings({ "unchecked", "rawtypes" })
private void freeEntry(Entry entry) {
private void freeEntry(Entry entry, boolean finalizer) {
PoolChunk chunk = entry.chunk;
long handle = entry.handle;
ByteBuffer nioBuffer = entry.nioBuffer;
// recycle now so PoolChunk can be GC'ed.
entry.recycle();
if (!finalizer) {
// recycle now so PoolChunk can be GC'ed. This will only be done if this is not freed because of
// a finalizer.
entry.recycle();
}
chunk.arena.freeChunk(chunk, handle, sizeClass, nioBuffer);
chunk.arena.freeChunk(chunk, handle, sizeClass, nioBuffer, finalizer);
}
static final class Entry<T> {

2
buffer/src/main/java/io/netty/buffer/PooledByteBufAllocator.java
View File

@ -474,7 +474,7 @@ public class PooledByteBufAllocator extends AbstractByteBufAllocator implements
@Override
protected void onRemoval(PoolThreadCache threadCache) {
threadCache.free();
threadCache.free(false);
}
private <T> PoolArena<T> leastUsedArena(PoolArena<T>[] arenas) {