[lldb] Make sure the process is stopped when computing the symbol context

[JDevlieghere]

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.

Depends on #135455

[llvmbot]

@llvm/pr-subscribers-lldb

Author: Jonas Devlieghere (JDevlieghere)

Changes

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.

Depends on #135455

---

Full diff: https://github.com/llvm/llvm-project/pull/135458.diff

1 Files Affected:

• (modified) lldb/source/Core/Statusline.cpp (+10-2)

diff --git a/lldb/source/Core/Statusline.cpp b/lldb/source/Core/Statusline.cpp
index ed5308ef53eb0..e14691e2538a2 100644
--- a/lldb/source/Core/Statusline.cpp
+++ b/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"
@@ -134,8 +135,15 @@ void Statusline::Redraw(bool update) {
     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())