From 7a2381dc2f8b40950d5041c9f4c9e04f6926403a Mon Sep 17 00:00:00 2001
From: Kris Borowinski <kris.borowinski@outlook.com>
Date: Fri, 25 Apr 2025 08:34:39 +0200
Subject: [PATCH] Fix the NREs when writing to console from multiple threads

---
 .../host/msh/ConsoleHostUserInterface.cs        | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/src/Microsoft.PowerShell.ConsoleHost/host/msh/ConsoleHostUserInterface.cs b/src/Microsoft.PowerShell.ConsoleHost/host/msh/ConsoleHostUserInterface.cs
index d81a435bd04..9587d6cd553 100644
--- a/src/Microsoft.PowerShell.ConsoleHost/host/msh/ConsoleHostUserInterface.cs
+++ b/src/Microsoft.PowerShell.ConsoleHost/host/msh/ConsoleHostUserInterface.cs
@@ -709,9 +709,14 @@ private void WriteLineToConsole()
         /// </exception>
         public override void Write(string value)
         {
-            WriteImpl(value, newLine: false);
+            lock (_instanceLock)
+            {
+                WriteImpl(value, newLine: false);
+            }
         }
 
+        // The WriteImpl() method should always be called within a lock on _instanceLock
+        // to ensure thread safety and prevent issues in multi-threaded scenarios.
         private void WriteImpl(string value, bool newLine)
         {
             if (string.IsNullOrEmpty(value) && !newLine)
@@ -845,7 +850,10 @@ private void Write(ConsoleColor foregroundColor, ConsoleColor backgroundColor, s
         /// </exception>
         public override void WriteLine(string value)
         {
-            this.WriteImpl(value, newLine: true);
+            lock (_instanceLock)
+            {
+                this.WriteImpl(value, newLine: true);
+            }
         }
 
         /// <summary>
@@ -862,7 +870,10 @@ public override void WriteLine(string value)
         /// </exception>
         public override void WriteLine()
         {
-            this.WriteImpl(Environment.NewLine, newLine: false);
+            lock (_instanceLock)
+            {
+                this.WriteImpl(Environment.NewLine, newLine: false);
+            }
         }
 
         #region Word Wrapping