Fix the NREs when writing to console from multiple threads (#25440)

kborowinski · web-flow · commit 658a8e45043f · 2025-04-25T13:34:13.000+05:00
The WriteImpl() method should always be called within a lock on _instanceLock to ensure thread safety.
diff --git 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

Original file line number	Diff line number	Diff line change
`@@ -709,9 +709,14 @@ private void WriteLineToConsole()`
`709`	`709`	`/// </exception>`
`710`	`710`	`public override void Write(string value)`
`711`	`711`	`{`
`712`		`- WriteImpl(value, newLine: false);`
	`712`	`+ lock (_instanceLock)`
	`713`	`+ {`
	`714`	`+ WriteImpl(value, newLine: false);`
	`715`	`+ }`
`713`	`716`	`}`
`714`	`717`
	`718`	`+ // The WriteImpl() method should always be called within a lock on _instanceLock`
	`719`	`+ // to ensure thread safety and prevent issues in multi-threaded scenarios.`
`715`	`720`	`private void WriteImpl(string value, bool newLine)`
`716`	`721`	`{`
`717`	`722`	`if (string.IsNullOrEmpty(value) && !newLine)`
`@@ -845,7 +850,10 @@ private void Write(ConsoleColor foregroundColor, ConsoleColor backgroundColor, s`
`845`	`850`	`/// </exception>`
`846`	`851`	`public override void WriteLine(string value)`
`847`	`852`	`{`
`848`		`- this.WriteImpl(value, newLine: true);`
	`853`	`+ lock (_instanceLock)`
	`854`	`+ {`
	`855`	`+ this.WriteImpl(value, newLine: true);`
	`856`	`+ }`
`849`	`857`	`}`
`850`	`858`
`851`	`859`	`/// <summary>`
`@@ -862,7 +870,10 @@ public override void WriteLine(string value)`
`862`	`870`	`/// </exception>`
`863`	`871`	`public override void WriteLine()`
`864`	`872`	`{`
`865`		`- this.WriteImpl(Environment.NewLine, newLine: false);`
	`873`	`+ lock (_instanceLock)`
	`874`	`+ {`
	`875`	`+ this.WriteImpl(Environment.NewLine, newLine: false);`
	`876`	`+ }`
`866`	`877`	`}`
`867`	`878`
`868`	`879`	`#region Word Wrapping`