[Lldb-commits] [lldb] [lldb] Fixed lldb-server crash (TestLogHandler was not thread safe) (PR #101326)

[Dmitry Vasilyev via lldb-commits]

https://github.com/slydiman created https://github.com/llvm/llvm-project/pull/101326

Host::LaunchProcess() requires to SetMonitorProcessCallback. This callback is called from the child process monitor thread. We cannot control this thread anyway. lldb-server may crash if there is a logging around this callback because TestLogHandler is not thread safe. I faced this issue debugging 100 simultaneous child processes. Note StreamLogHandler::Emit() in lldb/source/Utility/Log.cpp already contains the similar mutex.

>From 113340676cfd90867a272db0ba78f1385f00cb4c Mon Sep 17 00:00:00 2001
From: Dmitry Vasilyev <dvassiliev at accesssoftek.com>
Date: Wed, 31 Jul 2024 16:33:13 +0400
Subject: [PATCH] [lldb] Fixed lldb-server crash (TestLogHandler was not thread
 safe)

Host::LaunchProcess() requires to SetMonitorProcessCallback. This callback is called from the child process monitor thread. We cannot control this thread anyway. lldb-server may crash if there is a logging around this callback because TestLogHandler is not thread safe. I faced this issue debugging 100 simultaneous child processes. Note StreamLogHandler::Emit() in lldb/source/Utility/Log.cpp already contains the similar mutex.
---
 lldb/tools/lldb-server/LLDBServerUtilities.cpp | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lldb/tools/lldb-server/LLDBServerUtilities.cpp b/lldb/tools/lldb-server/LLDBServerUtilities.cpp
index c3a8df19e969e..5facfbf3105e9 100644
--- a/lldb/tools/lldb-server/LLDBServerUtilities.cpp
+++ b/lldb/tools/lldb-server/LLDBServerUtilities.cpp
@@ -27,11 +27,13 @@ class TestLogHandler : public LogHandler {
       : m_stream_sp(stream_sp) {}
 
   void Emit(llvm::StringRef message) override {
+    std::lock_guard<std::mutex> guard(m_mutex);
     (*m_stream_sp) << message;
     m_stream_sp->flush();
   }
 
 private:
+  std::mutex m_mutex;
   std::shared_ptr<raw_ostream> m_stream_sp;
 };