PaperMC/patches/unapplied/server/0752-Separate-lookup-locking-from-state-access-in-UserCac.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Spottedleaf <spottedleaf@spottedleaf.dev>
Date: Sat, 11 Jul 2020 05:09:28 -0700
Subject: [PATCH] Separate lookup locking from state access in UserCache

Prevent lookups from stalling simple state access/write calls

diff --git a/src/main/java/net/minecraft/server/players/GameProfileCache.java b/src/main/java/net/minecraft/server/players/GameProfileCache.java
index 61405c2b53e03a4b83e2c70c6e4d3739ca9676cb..66dfa8c844963091b63e1f2f85d0da6dd2cd083c 100644
--- a/src/main/java/net/minecraft/server/players/GameProfileCache.java
+++ b/src/main/java/net/minecraft/server/players/GameProfileCache.java
@@ -62,6 +62,11 @@ public class GameProfileCache {
     @Nullable
     private Executor executor;
 
+    // Paper start
+    protected final java.util.concurrent.locks.ReentrantLock stateLock = new java.util.concurrent.locks.ReentrantLock();
+    protected final java.util.concurrent.locks.ReentrantLock lookupLock = new java.util.concurrent.locks.ReentrantLock();
+    // Paper end
+
     public GameProfileCache(GameProfileRepository profileRepository, File cacheFile) {
         this.profileRepository = profileRepository;
         this.file = cacheFile;
@@ -69,6 +74,7 @@ public class GameProfileCache {
     }
 
     private void safeAdd(GameProfileCache.GameProfileInfo entry) {
+        try { this.stateLock.lock(); // Paper - allow better concurrency
         GameProfile gameprofile = entry.getProfile();
 
         entry.setLastAccess(this.getNextOperation());
@@ -83,6 +89,7 @@ public class GameProfileCache {
         if (uuid != null) {
             this.profilesByUUID.put(uuid, entry);
         }
+        } finally { this.stateLock.unlock(); } // Paper - allow better concurrency
 
     }
 
@@ -119,7 +126,7 @@ public class GameProfileCache {
         return com.destroystokyo.paper.PaperConfig.isProxyOnlineMode(); // Paper
     }
 
-    public synchronized void add(GameProfile profile) { // Paper - synchronize
+    public void add(GameProfile profile) { // Paper - synchronize // Paper - allow better concurrency
         Calendar calendar = Calendar.getInstance();
 
         calendar.setTime(new Date());
@@ -142,8 +149,9 @@ public class GameProfileCache {
     }
     // Paper end
 
-    public synchronized Optional<GameProfile> get(String name) { // Paper - synchronize
+    public Optional<GameProfile> get(String name) { // Paper - synchronize // Paper start - allow better concurrency
         String s1 = name.toLowerCase(Locale.ROOT);
+        boolean stateLocked = true; try { this.stateLock.lock(); // Paper - allow better concurrency
         GameProfileCache.GameProfileInfo usercache_usercacheentry = (GameProfileCache.GameProfileInfo) this.profilesByName.get(s1);
         boolean flag = false;
 
@@ -159,8 +167,12 @@ public class GameProfileCache {
         if (usercache_usercacheentry != null) {
             usercache_usercacheentry.setLastAccess(this.getNextOperation());
             optional = Optional.of(usercache_usercacheentry.getProfile());
+            stateLocked = false; this.stateLock.unlock(); // Paper - allow better concurrency
         } else {
+            stateLocked = false; this.stateLock.unlock(); // Paper - allow better concurrency
+            try { this.lookupLock.lock(); // Paper - allow better concurrency
             optional = GameProfileCache.lookupGameProfile(this.profileRepository, name); // Spigot - use correct case for offline players
+            } finally { this.lookupLock.unlock(); } // Paper - allow better concurrency
             if (optional.isPresent()) {
                 this.add((GameProfile) optional.get());
                 flag = false;
@@ -172,6 +184,7 @@ public class GameProfileCache {
         }
 
         return optional;
+        } finally { if (stateLocked) {  this.stateLock.unlock(); } } // Paper - allow better concurrency
     }
 
     public void getAsync(String username, Consumer<Optional<GameProfile>> consumer) {
@@ -198,6 +211,7 @@ public class GameProfileCache {
     }
 
     public Optional<GameProfile> get(UUID uuid) {
+        try { this.stateLock.lock(); // Paper - allow better concurrency
         GameProfileCache.GameProfileInfo usercache_usercacheentry = (GameProfileCache.GameProfileInfo) this.profilesByUUID.get(uuid);
 
         if (usercache_usercacheentry == null) {
@@ -206,6 +220,7 @@ public class GameProfileCache {
             usercache_usercacheentry.setLastAccess(this.getNextOperation());
             return Optional.of(usercache_usercacheentry.getProfile());
         }
+        } finally { this.stateLock.unlock(); } // Paper - allow better concurrency
     }
 
     public void setExecutor(Executor executor) {
@@ -322,7 +337,9 @@ public class GameProfileCache {
     }
 
     private Stream<GameProfileCache.GameProfileInfo> getTopMRUProfiles(int limit) {
+        try { this.stateLock.lock(); // Paper - allow better concurrency
         return ImmutableList.copyOf(this.profilesByUUID.values()).stream().sorted(Comparator.comparing(GameProfileCache.GameProfileInfo::getLastAccess).reversed()).limit((long) limit);
+        } finally { this.stateLock.unlock(); } // Paper - allow better concurrency
     }
 
     private static JsonElement writeGameProfile(GameProfileCache.GameProfileInfo entry, DateFormat dateFormat) {