Undo changes to Monitor.Enter/Exit

Bypass SyncTextWriter on single-threaded wasm to avoid compiling synchronization code during startup when console is touched

Author: kg

src/libraries/System.Console/src/System/Console.cs

@@ -235,16 +235,23 @@ static TextWriter EnsureInitialized()
 
         private static TextWriter CreateOutputWriter(Stream outputStream)
         {
-            return outputStream == Stream.Null ?
-                TextWriter.Null :
-                TextWriter.Synchronized(new StreamWriter(
-                    stream: outputStream,
-                    encoding: OutputEncoding.RemovePreamble(), // This ensures no prefix is written to the stream.
-                    bufferSize: WriteBufferSize,
-                    leaveOpen: true)
-                    {
-                        AutoFlush = true
-                    });
+            if (outputStream == Stream.Null)
+                return TextWriter.Null;
+
+            StreamWriter writer = new StreamWriter(
+                stream: outputStream,
+                encoding: OutputEncoding.RemovePreamble(), // This ensures no prefix is written to the stream.
+                bufferSize: WriteBufferSize,
+                leaveOpen: true
+            ) {
+                AutoFlush = true
+            };
+
+#if TARGET_BROWSER && !FEATURE_WASM_MANAGED_THREADS
+            return writer;
+#else
+            return TextWriter.Synchronized(writer);
+#endif
         }
 
         private static StrongBox<bool>? _isStdInRedirected;
@@ -702,7 +709,10 @@ public static void SetOut(TextWriter newOut)
             // are nops.
             if (newOut != TextWriter.Null)
             {
+#if TARGET_BROWSER && !FEATURE_WASM_MANAGED_THREADS
+#else
                 newOut = TextWriter.Synchronized(newOut);
+#endif
             }
 
             lock (s_syncObject)
@@ -719,7 +729,10 @@ public static void SetError(TextWriter newError)
             // Ensure all access to the writer is synchronized. See comment in SetOut.
             if (newError != TextWriter.Null)
             {
+#if TARGET_BROWSER && !FEATURE_WASM_MANAGED_THREADS
+#else
                 newError = TextWriter.Synchronized(newError);
+#endif
             }
 
             lock (s_syncObject)

src/libraries/System.Console/tests/SyncTextWriter.cs

@@ -13,6 +13,7 @@
 public class SyncTextWriter
 {
     [Fact]
+    [SkipOnPlatform(TestPlatforms.Browser, "Browser bypasses SyncTextWriter for faster startup")]
     public void SyncTextWriterLockedOnThis()
     {
         TextWriter oldWriter = Console.Out;

src/mono/System.Private.CoreLib/src/System/Threading/Monitor.Mono.cs

@@ -30,13 +30,10 @@ public static void Exit(object obj)
         {
             if (obj == null)
                 ArgumentNullException.ThrowIfNull(obj);
-#if TARGET_BROWSER && !FEATURE_WASM_MANAGED_THREADS
-#else
             if (ObjectHeader.TryExitChecked(obj))
                 return;
 
             InternalExit(obj);
-#endif
         }
 
         public static bool TryEnter(object obj)
@@ -160,16 +157,13 @@ private static void ReliableEnterTimeout(object obj, int timeout, ref bool lockT
             if (timeout < 0 && timeout != (int)Timeout.Infinite)
                 throw new ArgumentOutOfRangeException(nameof(timeout));
 
-#if TARGET_BROWSER && !FEATURE_WASM_MANAGED_THREADS
-#else
             // fast path
             if (ObjectHeader.TryEnterFast(obj)) {
                 lockTaken = true;
                 return;
             }
 
             try_enter_with_atomic_var(obj, timeout, true, ref lockTaken);
-#endif
         }
 
         public static long LockContentionCount => Monitor_get_lock_contention_count() + Lock.ContentionCount;