[Lldb-commits] [lldb] f67880a - [lldb-dap] Fix mutex acquisition order for modules event. (#163821)

[via lldb-commits]

Author: Ebuka Ezike
Date: 2025-10-22T17:37:59+01:00
New Revision: f67880ae3d23981c733383126267dd8e841d1ea9

URL: https://github.com/llvm/llvm-project/commit/f67880ae3d23981c733383126267dd8e841d1ea9
DIFF: https://github.com/llvm/llvm-project/commit/f67880ae3d23981c733383126267dd8e841d1ea9.diff

LOG: [lldb-dap] Fix mutex acquisition order for modules event. (#163821)

The modules event requires the `APIMutex` to create the module load
address. this may happen at the same time the `module request` is
handled.

The modules request also requires the `APIMutex` and the `modules_mutex,
set the order to acquire the mutexes.

Added: 
    

Modified: 
    lldb/tools/lldb-dap/DAP.cpp

Removed: 
    


################################################################################
diff  --git a/lldb/tools/lldb-dap/DAP.cpp b/lldb/tools/lldb-dap/DAP.cpp
index 52c8c6b9092b9..3c4f2253d1ad5 100644
--- a/lldb/tools/lldb-dap/DAP.cpp
+++ b/lldb/tools/lldb-dap/DAP.cpp
@@ -26,6 +26,7 @@
 #include "lldb/API/SBEvent.h"
 #include "lldb/API/SBLanguageRuntime.h"
 #include "lldb/API/SBListener.h"
+#include "lldb/API/SBMutex.h"
 #include "lldb/API/SBProcess.h"
 #include "lldb/API/SBStream.h"
 #include "lldb/Host/JSONTransport.h"
@@ -1452,7 +1453,11 @@ void DAP::EventThread() {
           const bool remove_module =
               event_mask & lldb::SBTarget::eBroadcastBitModulesUnloaded;
 
-          std::lock_guard<std::mutex> guard(modules_mutex);
+          // NOTE: Both mutexes must be acquired to prevent deadlock when
+          // handling `modules_request`, which also requires both locks.
+          lldb::SBMutex api_mutex = GetAPIMutex();
+          const std::scoped_lock<lldb::SBMutex, std::mutex> guard(
+              api_mutex, modules_mutex);
           for (uint32_t i = 0; i < num_modules; ++i) {
             lldb::SBModule module =
                 lldb::SBTarget::GetModuleAtIndexFromEvent(i, event);