[lldb] [Process/FreeBSDRemote] Remove thread name caching

[mgorny]

Summary

Remove the thread name caching code. It does not handle the possibility
of thread name changing between requests, therefore breaking
TestGdbRemoteThreadName. While technically we could cache the results
and reset the cache on resuming process, the gain from doing that
does not seem worth the effort.

[emaste]

Does Linux fetch each time also?
I agree it's probably not worth the effort.

[mgorny]

In D90863#2376742, @emaste wrote:

Does Linux fetch each time also?
I agree it's probably not worth the effort.

Yes. However, their logic is simpler (it boils down to opening a dedicated file in procfs (i.e. they don't have to iterate over all threads). Nevertheless, I don't think this is called frequently enough to justify optimization at this point.

lldb/source/Plugins/Process/FreeBSDRemote/NativeThreadFreeBSD.h

private:
   // Member Variables
   lldb::StateType m_state;
   ThreadStopInfo m_stop_info;
   std::unique_ptr<NativeRegisterContextFreeBSD> m_reg_context_up;
   std::string m_stop_description;
   using WatchpointIndexMap = std::map<lldb::addr_t, uint32_t>;
   WatchpointIndexMap m_watchpoint_index_map;
   WatchpointIndexMap m_hw_break_index_map;
-  llvm::Optional<std::string> m_thread_name;
 };
 
 typedef std::shared_ptr<NativeThreadFreeBSD> NativeThreadFreeBSDSP;
 } // namespace process_freebsd
 } // namespace lldb_private
 
 #endif // #ifndef liblldb_NativeThreadFreeBSD_H_

lldb/source/Plugins/Process/FreeBSDRemote/NativeThreadFreeBSD.cpp

 }
 
 void NativeThreadFreeBSD::SetStepping() {
   m_state = StateType::eStateStepping;
   m_stop_info.reason = StopReason::eStopReasonNone;
 }
 
 std::string NativeThreadFreeBSD::GetName() {
-  if (!m_thread_name) {
-    Log *log(ProcessPOSIXLog::GetLogIfAllCategoriesSet(POSIX_LOG_THREAD));
 
-    std::vector<struct kinfo_proc> kp;
-    int mib[4] = {CTL_KERN, KERN_PROC, KERN_PROC_PID | KERN_PROC_INC_THREAD,
-                  static_cast<int>(GetProcess().GetID())};
 
-    while (1) {
-      size_t len = kp.size() * sizeof(struct kinfo_proc);
-      void *ptr = len == 0 ? nullptr : kp.data();
-      int error = ::sysctl(mib, 4, ptr, &len, nullptr, 0);
-      if (ptr == nullptr || (error != 0 && errno == ENOMEM)) {
-        kp.resize(len / sizeof(struct kinfo_proc));
-        continue;
-      }
-      if (error != 0) {
-        len = 0;
-        LLDB_LOG(log, "tid = {0} in state {1} failed to get thread name: {2}", GetID(),
-                 m_state, strerror(errno));
-      }
-      kp.resize(len / sizeof(struct kinfo_proc));
-      break;
-    }
 
-    // empty == unknown
-    m_thread_name = std::string();
-    for (auto& procinfo : kp) {
-      if (procinfo.ki_tid == (lwpid_t)GetID()) {
-        m_thread_name = procinfo.ki_tdname;
-        break;
-      }
-    }
+    if (procinfo.ki_tid == static_cast<lwpid_t>(GetID()))
+      return procinfo.ki_tdname;
   }
 
-  return m_thread_name.getValue();
+  return "";
 }
 
 lldb::StateType NativeThreadFreeBSD::GetState() { return m_state; }
 
 bool NativeThreadFreeBSD::GetStopReason(ThreadStopInfo &stop_info,
                                         std::string &description) {
   Log *log(ProcessPOSIXLog::GetLogIfAllCategoriesSet(POSIX_LOG_THREAD));
   description.clear();

lldb/test/API/tools/lldb-server/thread-name/TestGdbRemoteThreadName.py

def run_and_check_name(self, expected_name):
         self.assertIsNotNone(context)
 
         sigint = lldbutil.get_signal_number("SIGINT")
         self.assertEqual(sigint, int(context.get("signal"), 16))
         kv_dict = self.parse_key_val_dict(context.get("key_vals_text"))
         self.assertEqual(expected_name, kv_dict.get("name"))
 
     @skipIfWindows # the test is not updated for Windows.
-    @expectedFailureAll(oslist=["freebsd"])
     @llgs_test
     def test(self):
         """ Make sure lldb-server can retrieve inferior thread name"""
         self.init_llgs_test()
         self.build()
         self.set_inferior_startup_launch()
         procs = self.prep_debug_monitor_and_inferior()
 
         self.run_and_check_name("hello world")
         self.run_and_check_name("goodbye world")