Index: lldb/packages/Python/lldbsuite/test/functionalities/thread/concurrent_events/TestConcurrentBreakpointOneDelayBreakpointThreads.py
===================================================================
--- lldb/packages/Python/lldbsuite/test/functionalities/thread/concurrent_events/TestConcurrentBreakpointOneDelayBreakpointThreads.py
+++ lldb/packages/Python/lldbsuite/test/functionalities/thread/concurrent_events/TestConcurrentBreakpointOneDelayBreakpointThreads.py
@@ -15,7 +15,6 @@
     @skipIfFreeBSD  # timing out on buildbot
     # Atomic sequences are not supported yet for MIPS in LLDB.
     @skipIf(triple='^mips')
-    @expectedFailureNetBSD
     def test(self):
         """Test threads that trigger a breakpoint where one thread has a 1 second delay. """
         self.build(dictionary=self.getBuildFlags())
Index: lldb/packages/Python/lldbsuite/test/functionalities/thread/concurrent_events/TestConcurrentCrashWithBreak.py
===================================================================
--- lldb/packages/Python/lldbsuite/test/functionalities/thread/concurrent_events/TestConcurrentCrashWithBreak.py
+++ lldb/packages/Python/lldbsuite/test/functionalities/thread/concurrent_events/TestConcurrentCrashWithBreak.py
@@ -15,7 +15,6 @@
     @skipIfFreeBSD  # timing out on buildbot
     # Atomic sequences are not supported yet for MIPS in LLDB.
     @skipIf(triple='^mips')
-    @expectedFailureNetBSD
     def test(self):
         """ Test a thread that crashes while another thread hits a breakpoint."""
         self.build(dictionary=self.getBuildFlags())
Index: lldb/packages/Python/lldbsuite/test/functionalities/thread/concurrent_events/TestConcurrentCrashWithSignal.py
===================================================================
--- lldb/packages/Python/lldbsuite/test/functionalities/thread/concurrent_events/TestConcurrentCrashWithSignal.py
+++ lldb/packages/Python/lldbsuite/test/functionalities/thread/concurrent_events/TestConcurrentCrashWithSignal.py
@@ -15,7 +15,6 @@
     @skipIfFreeBSD  # timing out on buildbot
     # Atomic sequences are not supported yet for MIPS in LLDB.
     @skipIf(triple='^mips')
-    @expectedFailureNetBSD
     def test(self):
         """ Test a thread that crashes while another thread generates a signal."""
         self.build(dictionary=self.getBuildFlags())
Index: lldb/packages/Python/lldbsuite/test/functionalities/thread/concurrent_events/TestConcurrentDelayedCrashWithBreakpointSignal.py
===================================================================
--- lldb/packages/Python/lldbsuite/test/functionalities/thread/concurrent_events/TestConcurrentDelayedCrashWithBreakpointSignal.py
+++ lldb/packages/Python/lldbsuite/test/functionalities/thread/concurrent_events/TestConcurrentDelayedCrashWithBreakpointSignal.py
@@ -15,7 +15,6 @@
     @skipIfFreeBSD  # timing out on buildbot
     # Atomic sequences are not supported yet for MIPS in LLDB.
     @skipIf(triple='^mips')
-    @expectedFailureNetBSD
     def test(self):
         """ Test a thread with a delayed crash while other threads generate a signal and hit a breakpoint. """
         self.build(dictionary=self.getBuildFlags())
Index: lldb/packages/Python/lldbsuite/test/functionalities/thread/concurrent_events/TestConcurrentTwoBreakpointThreads.py
===================================================================
--- lldb/packages/Python/lldbsuite/test/functionalities/thread/concurrent_events/TestConcurrentTwoBreakpointThreads.py
+++ lldb/packages/Python/lldbsuite/test/functionalities/thread/concurrent_events/TestConcurrentTwoBreakpointThreads.py
@@ -15,7 +15,6 @@
     @skipIfFreeBSD  # timing out on buildbot
     # Atomic sequences are not supported yet for MIPS in LLDB.
     @skipIf(triple='^mips')
-    @expectedFailureNetBSD
     def test(self):
         """Test two threads that trigger a breakpoint. """
         self.build(dictionary=self.getBuildFlags())
Index: lldb/packages/Python/lldbsuite/test/functionalities/thread/exit_during_step/TestExitDuringStep.py
===================================================================
--- lldb/packages/Python/lldbsuite/test/functionalities/thread/exit_during_step/TestExitDuringStep.py
+++ lldb/packages/Python/lldbsuite/test/functionalities/thread/exit_during_step/TestExitDuringStep.py
@@ -19,7 +19,6 @@
 
     @skipIfFreeBSD  # llvm.org/pr21411: test is hanging
     @skipIfWindows # This is flakey on Windows: llvm.org/pr38373
-    @expectedFailureNetBSD
     def test(self):
         """Test thread exit during step handling."""
         self.build(dictionary=self.getBuildFlags())
Index: lldb/packages/Python/lldbsuite/test/functionalities/thread/step_out/TestThreadStepOut.py
===================================================================
--- lldb/packages/Python/lldbsuite/test/functionalities/thread/step_out/TestThreadStepOut.py
+++ lldb/packages/Python/lldbsuite/test/functionalities/thread/step_out/TestThreadStepOut.py
@@ -27,7 +27,6 @@
         bugnumber="llvm.org/pr18066 inferior does not exit")
     @skipIfWindows # This test will hang on windows llvm.org/pr21753
     @expectedFailureAll(oslist=["windows"])
-    @expectedFailureNetBSD
     def test_step_single_thread(self):
         """Test thread step out on one thread via command interpreter. """
         self.build(dictionary=self.getBuildFlags())
@@ -44,7 +43,6 @@
     @skipIfWindows # This test will hang on windows llvm.org/pr21753
     @expectedFailureAll(oslist=["windows"])
     @expectedFailureAll(oslist=["watchos"], archs=['armv7k'], bugnumber="rdar://problem/34674488") # stop reason is trace when it should be step-out
-    @expectedFailureNetBSD
     def test_step_all_threads(self):
         """Test thread step out on all threads via command interpreter. """
         self.build(dictionary=self.getBuildFlags())
Index: lldb/source/Plugins/Process/NetBSD/NativeProcessNetBSD.h
===================================================================
--- lldb/source/Plugins/Process/NetBSD/NativeProcessNetBSD.h
+++ lldb/source/Plugins/Process/NetBSD/NativeProcessNetBSD.h
@@ -98,6 +98,7 @@
   bool HasThreadNoLock(lldb::tid_t thread_id);
 
   NativeThreadNetBSD &AddThread(lldb::tid_t thread_id);
+  void RemoveThread(lldb::tid_t thread_id);
 
   void MonitorCallback(lldb::pid_t pid, int signal);
   void MonitorExited(lldb::pid_t pid, WaitStatus status);
Index: lldb/source/Plugins/Process/NetBSD/NativeProcessNetBSD.cpp
===================================================================
--- lldb/source/Plugins/Process/NetBSD/NativeProcessNetBSD.cpp
+++ lldb/source/Plugins/Process/NetBSD/NativeProcessNetBSD.cpp
@@ -9,7 +9,6 @@
 #include "NativeProcessNetBSD.h"
 
 
-
 #include "Plugins/Process/POSIX/ProcessPOSIXLog.h"
 #include "lldb/Host/HostProcess.h"
 #include "lldb/Host/common/NativeRegisterContext.h"
@@ -99,6 +98,14 @@
       pid, launch_info.GetPTY().ReleaseMasterFileDescriptor(), native_delegate,
       Info.GetArchitecture(), mainloop));
 
+  // Enable event reporting
+  ptrace_event_t events;
+  // TODO: PTRACE_FORK | PTRACE_VFORK | PTRACE_POSIX_SPAWN?
+  events.pe_set_event = PTRACE_LWP_CREATE | PTRACE_LWP_EXIT;
+  status = PtraceWrapper(PT_SET_EVENT_MASK, pid, &events, sizeof(events));
+  if (status.Fail())
+    return status.ToError();
+
   status = process_up->ReinitializeThreads();
   if (status.Fail())
     return status.ToError();
@@ -238,6 +245,31 @@
       static_cast<NativeThreadNetBSD &>(*thread).SetStoppedByExec();
     SetState(StateType::eStateStopped, true);
   } break;
+  case TRAP_LWP: {
+    ptrace_state_t pst;
+    Status error = PtraceWrapper(PT_GET_PROCESS_STATE, GetID(), &pst,
+                                 sizeof(pst));
+    if (error.Fail()) {
+      SetState(StateType::eStateInvalid);
+      return;
+    }
+
+    switch (pst.pe_report_event) {
+      case PTRACE_LWP_CREATE:
+        AddThread(pst.pe_lwp);
+        break;
+      case PTRACE_LWP_EXIT:
+        RemoveThread(pst.pe_lwp);
+        break;
+    }
+
+    error = PtraceWrapper(PT_CONTINUE, GetID(), reinterpret_cast<void*>(1), 0);
+    if (error.Fail()) {
+      SetState(StateType::eStateInvalid);
+      return;
+    }
+    SetState(StateType::eStateRunning, true);
+  } break;
   case TRAP_DBREG: {
     // Find the thread.
     NativeThreadNetBSD* thread = nullptr;
@@ -694,6 +726,21 @@
   return static_cast<NativeThreadNetBSD &>(*m_threads.back());
 }
 
+void NativeProcessNetBSD::RemoveThread(lldb::tid_t thread_id) {
+  Log *log(ProcessPOSIXLog::GetLogIfAllCategoriesSet(POSIX_LOG_THREAD));
+  LLDB_LOG(log, "pid {0} removing thread with tid {1}", GetID(), thread_id);
+
+  assert(HasThreadNoLock(thread_id) &&
+         "attempted to remove a thread that does not exist");
+
+  for (auto it = m_threads.begin(); it != m_threads.end(); ++it) {
+    if (*it && ((*it)->GetID() == thread_id)) {
+      m_threads.erase(it);
+      break;
+    }
+  }
+}
+
 Status NativeProcessNetBSD::Attach() {
   // Attach to the requested process.
   // An attach will cause the thread to stop with a SIGSTOP.