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Fix NPE that was encounter by debugger (will never happen in real code). (#8992) 

Motivation:

We synchronize on the chunk.arena when produce the String returned by PoolSubpage.toString() which may raise a NPE when chunk == null. Chunk == null for the head of the linked-list and so a NPE may raised by a debugger. This NPE can never happen in real code tho as we never access toString() of the head.

Modifications:

Add null checks and so fix the possible NPE

Result:

No NPE when using a debugger and inspect the PooledByteBufAllocator.
This commit is contained in:
Norman Maurer 2019-04-01 19:44:28 +02:00 committed by GitHub
parent f7359aa742
commit a2b85a306d
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1 changed files with 33 additions and 10 deletions
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43
buffer/src/main/java/io/netty/buffer/PoolSubpage.java
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@ -204,16 +204,24 @@ final class PoolSubpage<T> implements PoolSubpageMetric {
final int maxNumElems;
final int numAvail;
final int elemSize;
synchronized (chunk.arena) {
if (!this.doNotDestroy) {
doNotDestroy = false;
// Not used for creating the String.
maxNumElems = numAvail = elemSize = -1;
} else {
doNotDestroy = true;
maxNumElems = this.maxNumElems;
numAvail = this.numAvail;
elemSize = this.elemSize;
if (chunk == null) {
// This is the head so there is no need to synchronize at all as these never change.
doNotDestroy = true;
maxNumElems = 0;
numAvail = 0;
elemSize = -1;
} else {
synchronized (chunk.arena) {
if (!this.doNotDestroy) {
doNotDestroy = false;
// Not used for creating the String.
maxNumElems = numAvail = elemSize = -1;
} else {
doNotDestroy = true;
maxNumElems = this.maxNumElems;
numAvail = this.numAvail;
elemSize = this.elemSize;
}
}
}
@ -227,6 +235,11 @@ final class PoolSubpage<T> implements PoolSubpageMetric {
@Override
public int maxNumElements() {
if (chunk == null) {
// It's the head.
return 0;
}
synchronized (chunk.arena) {
return maxNumElems;
}
@ -234,6 +247,11 @@ final class PoolSubpage<T> implements PoolSubpageMetric {
@Override
public int numAvailable() {
if (chunk == null) {
// It's the head.
return 0;
}
synchronized (chunk.arena) {
return numAvail;
}
@ -241,6 +259,11 @@ final class PoolSubpage<T> implements PoolSubpageMetric {
@Override
public int elementSize() {
if (chunk == null) {
// It's the head.
return -1;
}
synchronized (chunk.arena) {
return elemSize;
}