From 3f06210295051a413473e8f7d2b4a299c1f04635 Mon Sep 17 00:00:00 2001
From: Adrian McCarthy <amccarth@google.com>
Date: Mon, 22 Jul 2019 17:03:20 +0000
Subject: [PATCH] [Windows] Fix race condition between state changes

Patch by Martin Andersson (martin.andersson@evoma.se)

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.

Differential Revision: https://reviews.llvm.org/D62183

llvm-svn: 366703
---
 .../Process/Windows/Common/ProcessWindows.cpp | 21 +++++++++----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/lldb/source/Plugins/Process/Windows/Common/ProcessWindows.cpp b/lldb/source/Plugins/Process/Windows/Common/ProcessWindows.cpp
index 49801fecdb2c..7303e177b46c 100644
--- a/lldb/source/Plugins/Process/Windows/Common/ProcessWindows.cpp
+++ b/lldb/source/Plugins/Process/Windows/Common/ProcessWindows.cpp
@@ -205,16 +205,6 @@ Status ProcessWindows::DoResume() {
              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;
@@ -233,10 +223,19 @@ Status ProcessWindows::DoResume() {
 
     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(),