Paper/Spigot-Server-Patches/0390-Elide-lock-in-DataWatcher.patch
Spottedleaf 2f782a6652 Updated Upstream (CraftBukkit)
Upstream has released updates that appears to apply and compile correctly.
This update has not been tested by PaperMC and as with ANY update, please do your own testing

CraftBukkit Changes:
17543ecf SPIGOT-5035: Error Using Virtual Merchant GUI
0fc6922b SPIGOT-5028: Villager#setVillagerExperience() doesn't work
bdbdbe44 SPIGOT-5024: Fox error - Unknown target reason
2019-06-06 16:56:51 +01:00

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5.0 KiB
Diff

From 768c42f5349250c4aff1ecf2acab4f334e0a169b Mon Sep 17 00:00:00 2001
From: Spottedleaf <Spottedleaf@users.noreply.github.com>
Date: Sat, 11 May 2019 08:19:27 -0700
Subject: [PATCH] Elide lock in DataWatcher
The lock in DataWatcher is used to prevent concurrent modifications
to the 'd' field (entries in MCP). However any modifications to
this map only occur on initialization of an Entity in its
constructor. This modification is write-locked.
Every other access is through a readlock, which allows
the threads to pass if there is no thread holding the
writelock.
Since the writelock is only obtained in the constructor
of the Entity, the further readlocks are actually
useless (which get obtained on set, get, etc calls).
diff --git a/src/main/java/net/minecraft/server/DataWatcher.java b/src/main/java/net/minecraft/server/DataWatcher.java
index f224043d8e..bbea8ef726 100644
--- a/src/main/java/net/minecraft/server/DataWatcher.java
+++ b/src/main/java/net/minecraft/server/DataWatcher.java
@@ -23,7 +23,7 @@ public class DataWatcher {
private static final Map<Class<? extends Entity>, Integer> b = Maps.newHashMap();
private final Entity c;
private final Int2ObjectOpenHashMap<DataWatcher.Item<?>> d = new Int2ObjectOpenHashMap<>(); // Paper
- private final ReadWriteLock e = new ReentrantReadWriteLock();
+ //private final ReadWriteLock e = new ReentrantReadWriteLock(); // Paper - not required
private boolean f = true;
private boolean g;
@@ -88,30 +88,14 @@ public class DataWatcher {
private <T> void registerObject(DataWatcherObject<T> datawatcherobject, T t0) {
DataWatcher.Item<T> datawatcher_item = new DataWatcher.Item<>(datawatcherobject, t0);
- this.e.writeLock().lock();
+ //this.e.writeLock().lock(); // Paper - not required
this.d.put(datawatcherobject.a(), datawatcher_item);
this.f = false;
- this.e.writeLock().unlock();
+ //this.e.writeLock().unlock(); // Paper - not required
}
private <T> DataWatcher.Item<T> b(DataWatcherObject<T> datawatcherobject) {
- this.e.readLock().lock();
-
- DataWatcher.Item datawatcher_item;
-
- try {
- datawatcher_item = (DataWatcher.Item) this.d.get(datawatcherobject.a());
- } catch (Throwable throwable) {
- CrashReport crashreport = CrashReport.a(throwable, "Getting synched entity data");
- CrashReportSystemDetails crashreportsystemdetails = crashreport.a("Synched entity data");
-
- crashreportsystemdetails.a("Data ID", (Object) datawatcherobject);
- throw new ReportedException(crashreport);
- } finally {
- this.e.readLock().unlock();
- }
-
- return datawatcher_item;
+ return (DataWatcher.Item<T>)this.d.get(datawatcherobject.a()); // Paper - avoid lock and try catch, get() does not fail
}
public <T> T get(DataWatcherObject<T> datawatcherobject) {
@@ -158,7 +142,7 @@ public class DataWatcher {
List<DataWatcher.Item<?>> list = null;
if (this.g) {
- this.e.readLock().lock();
+ //this.e.readLock().lock(); // Paper - not required
Iterator iterator = this.d.values().iterator();
while (iterator.hasNext()) {
@@ -174,7 +158,7 @@ public class DataWatcher {
}
}
- this.e.readLock().unlock();
+ //this.e.readLock().unlock(); // Paper - not required
}
this.g = false;
@@ -182,7 +166,7 @@ public class DataWatcher {
}
public void a(PacketDataSerializer packetdataserializer) throws IOException {
- this.e.readLock().lock();
+ //this.e.readLock().lock(); // Paper - not required
Iterator iterator = this.d.values().iterator();
while (iterator.hasNext()) {
@@ -191,7 +175,7 @@ public class DataWatcher {
a(packetdataserializer, datawatcher_item);
}
- this.e.readLock().unlock();
+ //this.e.readLock().unlock(); // Paper - not required
packetdataserializer.writeByte(255);
}
@@ -199,7 +183,7 @@ public class DataWatcher {
public List<DataWatcher.Item<?>> c() {
List<DataWatcher.Item<?>> list = null;
- this.e.readLock().lock();
+ //this.e.readLock().lock(); // Paper - not required
DataWatcher.Item datawatcher_item;
@@ -210,7 +194,7 @@ public class DataWatcher {
}
}
- this.e.readLock().unlock();
+ //this.e.readLock().unlock(); // Paper - not required
return list;
}
@@ -261,7 +245,7 @@ public class DataWatcher {
public void e() {
this.g = false;
- this.e.readLock().lock();
+ //this.e.readLock().lock(); // Paper - not required
Iterator iterator = this.d.values().iterator();
while (iterator.hasNext()) {
@@ -270,7 +254,7 @@ public class DataWatcher {
datawatcher_item.a(false);
}
- this.e.readLock().unlock();
+ //this.e.readLock().unlock(); // Paper - not required
}
public static class Item<T> {
--
2.21.0