[Lldb-commits] [lldb] [lldb] Synchronize access to m_statusline in the Debugger (PR #134759)

[Jonas Devlieghere via lldb-commits]

https://github.com/JDevlieghere updated 
https://github.com/llvm/llvm-project/pull/134759

>From 9fcc1c89ff0361d9262abefe951b43dd37555fea Mon Sep 17 00:00:00 2001
From: Jonas Devlieghere <jo...@devlieghere.com>
Date: Thu, 10 Apr 2025 11:13:12 -0700
Subject: [PATCH] [lldb] Synchronize access to m_statusline in the Debugger

Eliminate the potential for a race between the main thread, the default
event handler thread and the signal handling thread, when accessing the
m_statusline member.
---
 lldb/include/lldb/Core/Debugger.h |  2 ++
 lldb/source/Core/Debugger.cpp     | 46 +++++++++++++++++++++++--------
 2 files changed, 36 insertions(+), 12 deletions(-)

diff --git a/lldb/include/lldb/Core/Debugger.h 
b/lldb/include/lldb/Core/Debugger.h
index c79a75ab61564..5932454f366b8 100644
--- a/lldb/include/lldb/Core/Debugger.h
+++ b/lldb/include/lldb/Core/Debugger.h
@@ -751,6 +751,8 @@ class Debugger : public 
std::enable_shared_from_this<Debugger>,
   IOHandlerStack m_io_handler_stack;
   std::recursive_mutex m_io_handler_synchronous_mutex;
 
+  /// Mutex protecting the m_statusline member.
+  std::mutex m_statusline_mutex;
   std::optional<Statusline> m_statusline;
 
   llvm::StringMap<std::weak_ptr<LogHandler>> m_stream_handlers;
diff --git a/lldb/source/Core/Debugger.cpp b/lldb/source/Core/Debugger.cpp
index 51029f91eb12d..5e5918a6091d9 100644
--- a/lldb/source/Core/Debugger.cpp
+++ b/lldb/source/Core/Debugger.cpp
@@ -251,6 +251,7 @@ Status Debugger::SetPropertyValue(const ExecutionContext 
*exe_ctx,
                g_debugger_properties[ePropertyShowStatusline].name) {
       // Statusline setting changed. If we have a statusline instance, update 
it
       // now. Otherwise it will get created in the default event handler.
+      std::lock_guard<std::mutex> guard(m_statusline_mutex);
       if (StatuslineSupported())
         m_statusline.emplace(*this);
       else
@@ -391,8 +392,12 @@ bool Debugger::SetTerminalWidth(uint64_t term_width) {
 
   if (auto handler_sp = m_io_handler_stack.Top())
     handler_sp->TerminalSizeChanged();
-  if (m_statusline)
-    m_statusline->TerminalSizeChanged();
+
+  {
+    std::lock_guard<std::mutex> guard(m_statusline_mutex);
+    if (m_statusline)
+      m_statusline->TerminalSizeChanged();
+  }
 
   return success;
 }
@@ -409,8 +414,12 @@ bool Debugger::SetTerminalHeight(uint64_t term_height) {
 
   if (auto handler_sp = m_io_handler_stack.Top())
     handler_sp->TerminalSizeChanged();
-  if (m_statusline)
-    m_statusline->TerminalSizeChanged();
+
+  {
+    std::lock_guard<std::mutex> guard(m_statusline_mutex);
+    if (m_statusline)
+      m_statusline->TerminalSizeChanged();
+  }
 
   return success;
 }
@@ -1141,8 +1150,11 @@ void Debugger::SetErrorFile(FileSP file_sp) {
 }
 
 void Debugger::SaveInputTerminalState() {
-  if (m_statusline)
-    m_statusline->Disable();
+  {
+    std::lock_guard<std::mutex> guard(m_statusline_mutex);
+    if (m_statusline)
+      m_statusline->Disable();
+  }
   int fd = GetInputFile().GetDescriptor();
   if (fd != File::kInvalidDescriptor)
     m_terminal_state.Save(fd, true);
@@ -1150,11 +1162,15 @@ void Debugger::SaveInputTerminalState() {
 
 void Debugger::RestoreInputTerminalState() {
   m_terminal_state.Restore();
-  if (m_statusline)
-    m_statusline->Enable();
+  {
+    std::lock_guard<std::mutex> guard(m_statusline_mutex);
+    if (m_statusline)
+      m_statusline->Enable();
+  }
 }
 
 void Debugger::RedrawStatusline(bool update) {
+  std::lock_guard<std::mutex> guard(m_statusline_mutex);
   if (m_statusline)
     m_statusline->Redraw(update);
 }
@@ -2032,8 +2048,11 @@ lldb::thread_result_t Debugger::DefaultEventHandler() {
   // are now listening to all required events so no events get missed
   m_sync_broadcaster.BroadcastEvent(eBroadcastBitEventThreadIsListening);
 
-  if (!m_statusline && StatuslineSupported())
-    m_statusline.emplace(*this);
+  if (StatuslineSupported()) {
+    std::lock_guard<std::mutex> guard(m_statusline_mutex);
+    if (!m_statusline)
+      m_statusline.emplace(*this);
+  }
 
   bool done = false;
   while (!done) {
@@ -2094,8 +2113,11 @@ lldb::thread_result_t Debugger::DefaultEventHandler() {
     }
   }
 
-  if (m_statusline)
-    m_statusline.reset();
+  {
+    std::lock_guard<std::mutex> guard(m_statusline_mutex);
+    if (m_statusline)
+      m_statusline.reset();
+  }
 
   return {};
 }

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