[lldb] Fix data race when interacting with python scripts

This patch should fix some data races when a python script (i.e. a
Scripted Process) has a nested call to another python script (i.e. a
OperatingSystem Plugin), which can cause concurrent writes to the python
lock count.

This patch also fixes a data race happening when resetting the operating
system unique pointer.

To address these issues, both accesses is guarded by a mutex.

rdar://109413039

Differential Revision: https://reviews.llvm.org/D154271

Signed-off-by: Med Ismail Bennani <[email protected]>

Author: medismailben

lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPythonImpl.h

@@ -378,11 +378,18 @@ class ScriptInterpreterPythonImpl : public ScriptInterpreterPython {
 
   void LeaveSession();
 
-  uint32_t IsExecutingPython() const { return m_lock_count > 0; }
+  uint32_t IsExecutingPython() {
+    std::lock_guard<std::mutex> guard(m_mutex);
+    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 +429,7 @@ class ScriptInterpreterPythonImpl : public ScriptInterpreterPython {
   bool m_pty_secondary_is_open;
   bool m_valid_session;
   uint32_t m_lock_count;
+  std::mutex m_mutex;
   PyThreadState *m_command_thread_state;
 };
 

lldb/source/Target/Process.cpp

@@ -2467,6 +2467,7 @@ Process::WaitForProcessStopPrivate(EventSP &event_sp,
 }
 
 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));