[Lldb-commits] [PATCH] D154271: [lldb] Fix data race when interacting with python scripts

[Med Ismail Bennani via Phabricator via lldb-commits]

mib updated this revision to Diff 536850.
mib added a comment.

After chatting with Jonas, it turns out that my previous implementation didn't 
actually address the underflow issue using atomics, so we have to revert to 
using a `std::mutex` when incrementing/decrementing the python lock counter.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D154271/new/

https://reviews.llvm.org/D154271

Files:
  lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPythonImpl.h
  lldb/source/Target/Process.cpp


Index: lldb/source/Target/Process.cpp
===================================================================
--- lldb/source/Target/Process.cpp
+++ lldb/source/Target/Process.cpp
@@ -2467,6 +2467,7 @@
 }
 
 void Process::LoadOperatingSystemPlugin(bool flush) {
+  std::lock_guard<std::recursive_mutex> guard(m_thread_mutex);
   if (flush)
     m_thread_list.Clear();
   m_os_up.reset(OperatingSystem::FindPlugin(this, nullptr));
Index: 
lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPythonImpl.h
===================================================================
--- lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPythonImpl.h
+++ lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPythonImpl.h
@@ -380,9 +380,13 @@
 
   uint32_t IsExecutingPython() const { return m_lock_count > 0; }
 
-  uint32_t IncrementLockCount() { return ++m_lock_count; }
+  uint32_t IncrementLockCount() {
+    std::lock_guard<std::mutex> guard(m_mutex);
+    return ++m_lock_count;
+  }
 
   uint32_t DecrementLockCount() {
+    std::lock_guard<std::mutex> guard(m_mutex);
     if (m_lock_count > 0)
       --m_lock_count;
     return m_lock_count;
@@ -422,6 +426,7 @@
   bool m_pty_secondary_is_open;
   bool m_valid_session;
   uint32_t m_lock_count;
+  std::mutex m_mutex;
   PyThreadState *m_command_thread_state;
 };
 



Index: lldb/source/Target/Process.cpp
===================================================================
--- lldb/source/Target/Process.cpp
+++ lldb/source/Target/Process.cpp
@@ -2467,6 +2467,7 @@
 }
 
 void Process::LoadOperatingSystemPlugin(bool flush) {
+  std::lock_guard<std::recursive_mutex> guard(m_thread_mutex);
   if (flush)
     m_thread_list.Clear();
   m_os_up.reset(OperatingSystem::FindPlugin(this, nullptr));
Index: lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPythonImpl.h
===================================================================
--- lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPythonImpl.h
+++ lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPythonImpl.h
@@ -380,9 +380,13 @@
 
   uint32_t IsExecutingPython() const { return m_lock_count > 0; }
 
-  uint32_t IncrementLockCount() { return ++m_lock_count; }
+  uint32_t IncrementLockCount() {
+    std::lock_guard<std::mutex> guard(m_mutex);
+    return ++m_lock_count;
+  }
 
   uint32_t DecrementLockCount() {
+    std::lock_guard<std::mutex> guard(m_mutex);
     if (m_lock_count > 0)
       --m_lock_count;
     return m_lock_count;
@@ -422,6 +426,7 @@
   bool m_pty_secondary_is_open;
   bool m_valid_session;
   uint32_t m_lock_count;
+  std::mutex m_mutex;
   PyThreadState *m_command_thread_state;
 };
 

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