[lldb] Make sure the process is stopped when computing the symbol context (#134757)

Make sure the process is stopped when computing the symbol context. Both
Adrian and Felipe reported a handful of crashes in GetSymbolContext
called from Statusline::Redraw on the default event thread.

Given that we're handling a StackFrameSP, it's not clear to me how that
could have gotten invalidated, but Jim points out that it doesn't make
sense to compute the symbol context for the frame when the process isn't
stopped.

Author: JDevlieghere

lldb/source/Core/Statusline.cpp

@@ -12,6 +12,7 @@
 #include "lldb/Host/StreamFile.h"
 #include "lldb/Interpreter/CommandInterpreter.h"
 #include "lldb/Symbol/SymbolContext.h"
+#include "lldb/Target/Process.h"
 #include "lldb/Target/StackFrame.h"
 #include "lldb/Utility/AnsiTerminal.h"
 #include "lldb/Utility/StreamString.h"
@@ -126,19 +127,25 @@ void Statusline::Redraw(bool update) {
     return;
   }
 
-  StreamString stream;
-  ExecutionContext exe_ctx =
-      m_debugger.GetCommandInterpreter().GetExecutionContext();
+  ExecutionContext exe_ctx = m_debugger.GetSelectedExecutionContext();
 
   // For colors and progress events, the format entity needs access to the
   // debugger, which requires a target in the execution context.
   if (!exe_ctx.HasTargetScope())
     exe_ctx.SetTargetPtr(&m_debugger.GetSelectedOrDummyTarget());
 
   SymbolContext symbol_ctx;
-  if (auto frame_sp = exe_ctx.GetFrameSP())
-    symbol_ctx = frame_sp->GetSymbolContext(eSymbolContextEverything);
+  if (ProcessSP process_sp = exe_ctx.GetProcessSP()) {
+    // Check if the process is stopped, and if it is, make sure it remains
+    // stopped until we've computed the symbol context.
+    Process::StopLocker stop_locker;
+    if (stop_locker.TryLock(&process_sp->GetRunLock())) {
+      if (auto frame_sp = exe_ctx.GetFrameSP())
+        symbol_ctx = frame_sp->GetSymbolContext(eSymbolContextEverything);
+    }
+  }
 
+  StreamString stream;
   if (auto *format = m_debugger.GetStatuslineFormat())
     FormatEntity::Format(*format, stream, &symbol_ctx, &exe_ctx, nullptr,
                          nullptr, false, false);