From 29ea68399db665befa6800794b39eb41b4647799 Mon Sep 17 00:00:00 2001
From: Igor Bagdamyan <37334640+En3Tho@users.noreply.github.com>
Date: Wed, 28 Aug 2024 21:08:52 +0300
Subject: [PATCH] A small fix to preserve thread ids when parallel stack is
 shared (#4893)

Sometimes a stack can be shared in a way where some thread's top frame
is the current frame but there are still frames/threads present in the
stack
In this case print the unique thread ids in the current stack frame.
Otherwise this information is lost:
```
~~ Thread_T1 - unique thread id(s) for the current frame, this thread id is not currently displayed
    ~~ Thread_T2
    1 Next_Stack_Frame
2 Current_Stack_Frame - this is actually a top frame for thread T1
```

Another way would be printing in a slightly different order but it will
chop stack a little:
```
    ~~ Thread_T2
    1 Next_Stack_Frame
~~ Thread_T1
2 Current_Stack_Frame
```
---
 .../ParallelStacks.Runtime/RendererHelpers.cs       | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/src/Microsoft.Diagnostics.ExtensionCommands/ParallelStacks.Runtime/RendererHelpers.cs b/src/Microsoft.Diagnostics.ExtensionCommands/ParallelStacks.Runtime/RendererHelpers.cs
index e3f0cc180..464e0f3ee 100644
--- a/src/Microsoft.Diagnostics.ExtensionCommands/ParallelStacks.Runtime/RendererHelpers.cs
+++ b/src/Microsoft.Diagnostics.ExtensionCommands/ParallelStacks.Runtime/RendererHelpers.cs
@@ -29,6 +29,19 @@ namespace ParallelStacks.Runtime
                 return;
             }
 
+            // Sometimes a stack can be shared in a way where some threads top frame is the current frame but there are still frames/threads present in the stack
+            // In this case print the unique thread ids in the current stack frame e.g.
+            // ~~ Thread_T1 - this one is the unique thread id for the current frame
+            //   ~~ Thread_T2
+            //   1 Next_Stack_Frame
+            // 2 Current_Stack_Frame
+            if (stack.Stacks.Count == 1 && stack.Stacks[0].ThreadIds.Count != stack.ThreadIds.Count)
+            {
+                List<uint> uniqueThreads = stack.ThreadIds.Except(stack.Stacks[0].ThreadIds).ToList();
+                visitor.Write($"{Environment.NewLine}{alignment}");
+                visitor.WriteFrameSeparator($" ~~~~ {FormatThreadIdList(visitor, uniqueThreads)}");
+            }
+
             foreach (ParallelStack nextStackFrame in stack.Stacks.OrderBy(s => s.ThreadIds.Count))
             {
                 RenderStack(nextStackFrame, visitor,
-- 
2.34.1