Fix multiprocessing debug with breakpoints in both main and child processes (PY-17092)

When the new process is created, the main thread in the new process already has the attribute '__pydevd_id__', so the new thread doesn't get new id with its process number and the debugger loses access to both threads. Therefore we should update thread_id for every main thread in the new process.

python/helpers/pydev/pydevd.py

@@ -556,14 +556,17 @@ class PyDB:
             self._lock_running_thread_ids.acquire()
             try:
                 for t in all_threads:
-                    thread_id = GetThreadId(t)
-
                     if getattr(t, 'is_pydev_daemon_thread', False):
                         pass # I.e.: skip the DummyThreads created from pydev daemon threads
                     elif isinstance(t, PyDBDaemonThread):
                         pydev_log.error_once('Error in debugger: Found PyDBDaemonThread not marked with is_pydev_daemon_thread=True.\n')
 
                     elif isThreadAlive(t):
+                        if not self._running_thread_ids:
+                            thread_id = GetThreadId(t, True)
+                            curr_thread_id = GetThreadId(threadingCurrentThread())
+                        else:
+                            thread_id = GetThreadId(t)
                         program_threads_alive[thread_id] = t
 
                         if not DictContains(self._running_thread_ids, thread_id):

python/helpers/pydev/pydevd_constants.py

@@ -195,29 +195,38 @@ class NextId:
 
 _nextThreadId = NextId()
 
+
+#=======================================================================================================================
+# GetPid
+#=======================================================================================================================
+def GetPid():
+    try:
+        return os.getpid()
+    except AttributeError:
+        try:
+            #Jython does not have it!
+            import java.lang.management.ManagementFactory  #@UnresolvedImport -- just for jython
+            pid = java.lang.management.ManagementFactory.getRuntimeMXBean().getName()
+            return pid.replace('@', '_')
+        except:
+            #ok, no pid available (will be unable to debug multiple processes)
+            return '000001'
+
+
 #=======================================================================================================================
 # GetThreadId
 #=======================================================================================================================
-def GetThreadId(thread):
+def GetThreadId(thread, update_pydevd_id=False):
     try:
+        if update_pydevd_id:
+            del thread.__pydevd_id__
         return thread.__pydevd_id__
     except AttributeError:
         _nextThreadIdLock.acquire()
         try:
             #We do a new check with the lock in place just to be sure that nothing changed
             if not hasattr(thread, '__pydevd_id__'):
-                try:
-                    pid = os.getpid()
-                except AttributeError:
-                    try:
-                        #Jython does not have it!
-                        import java.lang.management.ManagementFactory  #@UnresolvedImport -- just for jython
-                        pid = java.lang.management.ManagementFactory.getRuntimeMXBean().getName()
-                        pid = pid.replace('@', '_')
-                    except:
-                        #ok, no pid available (will be unable to debug multiple processes)
-                        pid = '000001'
-
+                pid = GetPid()
                 thread.__pydevd_id__ = 'pid%s_seq%s' % (pid, _nextThreadId())
         finally:
             _nextThreadIdLock.release()