[Lldb-commits] [lldb] [vscode-lldb] Fix race condition when changing lldb-dap arguments (PR #151828)

[via lldb-commits]

https://github.com/royitaqi created https://github.com/llvm/llvm-project/pull/151828

# Problem

When the user changes lldb-dap's arguments (e.g. path), there is a race condition, where the new lldb-dap process could be started first and have set the extension's `serverProcess` and `serverInfo` according to the new process, while the old lldb-dap process exits later and wipes out these two fields.

Consequences:
1. This causes `getServerProcess()` to return `undefined` when it should return the new process.
2. This also causes wrong behavior in the next debug session that a new lldb-dap process will be started and the old not reused nor killed.

# Fix

When wiping the two fields, check if `serverProcess` equals to the process captured by the handler. If they equal, wipe the fields. If not, then the fields have already been updated (either new process has started, or the fields were already wiped out by another handler), and so the wiping should be skipped.

>From b58e5d4fe42a499dc7b9d903f56d62fc993f67a2 Mon Sep 17 00:00:00 2001
From: Roy Shi <royshi at meta.com>
Date: Sat, 2 Aug 2025 09:30:25 -0700
Subject: [PATCH] [vscode-lldb] Fix race condition when changing lldb-dap
 arguments

---
 lldb/tools/lldb-dap/src-ts/lldb-dap-server.ts | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/lldb/tools/lldb-dap/src-ts/lldb-dap-server.ts b/lldb/tools/lldb-dap/src-ts/lldb-dap-server.ts
index 79573ec7342b1..c4e99a3178e8c 100644
--- a/lldb/tools/lldb-dap/src-ts/lldb-dap-server.ts
+++ b/lldb/tools/lldb-dap/src-ts/lldb-dap-server.ts
@@ -39,8 +39,10 @@ export class LLDBDapServer implements vscode.Disposable {
       const process = child_process.spawn(dapPath, dapArgs, options);
       process.on("error", (error) => {
         reject(error);
-        this.serverProcess = undefined;
-        this.serverInfo = undefined;
+        if (this.serverProcess === process) {
+          this.serverProcess = undefined;
+          this.serverInfo = undefined;
+        }
       });
       process.on("exit", (code, signal) => {
         let errorMessage = "Server process exited early";
@@ -50,8 +52,10 @@ export class LLDBDapServer implements vscode.Disposable {
           errorMessage += ` due to signal ${signal}`;
         }
         reject(new Error(errorMessage));
-        this.serverProcess = undefined;
-        this.serverInfo = undefined;
+        if (this.serverProcess === process) {
+          this.serverProcess = undefined;
+          this.serverInfo = undefined;
+        }
       });
       process.stdout.setEncoding("utf8").on("data", (data) => {
         const connection = /connection:\/\/\[([^\]]+)\]:(\d+)/.exec(