[Lldb-commits] [PATCH] D62183: [Windows] Fix race condition between state changes

[Martin Andersson via Phabricator via lldb-commits]

martin created this revision.
martin added a reviewer: zturner.
Herald added a project: LLDB.
Herald added a subscriber: lldb-commits.

If the process is resumed before the state is changed to "running" there is a possibility (when single stepping) that the debugger stops and changes the state to "stopped" before it is first changed to "running". This causes the process to ignore the stop event (since the state did not change) which in turn leads the DebuggerThread to wait indefinitely for the exception predicate in HandleExceptionEvent.


Repository:
  rLLDB LLDB

https://reviews.llvm.org/D62183

Files:
  source/Plugins/Process/Windows/Common/ProcessWindows.cpp


Index: source/Plugins/Process/Windows/Common/ProcessWindows.cpp
===================================================================
--- source/Plugins/Process/Windows/Common/ProcessWindows.cpp
+++ source/Plugins/Process/Windows/Common/ProcessWindows.cpp
@@ -359,16 +359,6 @@
              m_session_data->m_debugger->GetProcess().GetProcessId(),
              GetPrivateState());
 
-    ExceptionRecordSP active_exception =
-        m_session_data->m_debugger->GetActiveException().lock();
-    if (active_exception) {
-      // Resume the process and continue processing debug events.  Mask the
-      // exception so that from the process's view, there is no indication that
-      // anything happened.
-      m_session_data->m_debugger->ContinueAsyncException(
-          ExceptionResult::MaskException);
-    }
-
     LLDB_LOG(log, "resuming {0} threads.", m_thread_list.GetSize());
 
     bool failed = false;
@@ -387,10 +377,19 @@
 
     if (failed) {
       error.SetErrorString("ProcessWindows::DoResume failed");
-      return error;
     } else {
       SetPrivateState(eStateRunning);
     }
+
+    ExceptionRecordSP active_exception =
+        m_session_data->m_debugger->GetActiveException().lock();
+    if (active_exception) {
+      // Resume the process and continue processing debug events.  Mask the
+      // exception so that from the process's view, there is no indication that
+      // anything happened.
+      m_session_data->m_debugger->ContinueAsyncException(
+          ExceptionResult::MaskException);
+    }
   } else {
     LLDB_LOG(log, "error: process {0} is in state {1}.  Returning...",
              m_session_data->m_debugger->GetProcess().GetProcessId(),


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