[lldb] Fix data race when interacting with python scripts

medismailben · medismailben · commit f0cbf4d16a93 · 2023-07-03T11:51:34.000-07:00
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 <ismail@bennani.ma>
diff --git a/lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPythonImpl.h b/lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPythonImpl.h
@@ -375,11 +375,18 @@ 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;
@@ -419,6 +426,7 @@ 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;
 };
 
diff --git a/lldb/source/Target/Process.cpp b/lldb/source/Target/Process.cpp
@@ -2609,6 +2609,7 @@ 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));

Original file line number	Diff line number	Diff line change
`@@ -2609,6 +2609,7 @@ Process::WaitForProcessStopPrivate(EventSP &event_sp,`
`2609`	`2609`	`}`
`2610`	`2610`
`2611`	`2611`	`void Process::LoadOperatingSystemPlugin(bool flush) {`
	`2612`	`+ std::lock_guard<std::recursive_mutex> guard(m_thread_mutex);`
`2612`	`2613`	`if (flush)`
`2613`	`2614`	`m_thread_list.Clear();`
`2614`	`2615`	`m_os_up.reset(OperatingSystem::FindPlugin(this, nullptr));`