[NFC][dfsan] Split Init and ThreadStart

Author: vitalybuka

compiler-rt/lib/dfsan/dfsan.cpp

@@ -991,7 +991,7 @@ static void DFsanInit(int argc, char **argv, char **envp) {
 
   DFsanThread *main_thread = DFsanThread::Create(nullptr, nullptr, nullptr);
   SetCurrentThread(main_thread);
-  main_thread->ThreadStart();
+  main_thread->Init();
 
   dfsan_init_is_running = false;
   dfsan_inited = true;

compiler-rt/lib/dfsan/dfsan_custom.cpp

@@ -755,6 +755,7 @@ SANITIZER_INTERFACE_ATTRIBUTE void *__dfso_dlopen(
 static void *DFsanThreadStartFunc(void *arg) {
   DFsanThread *t = (DFsanThread *)arg;
   SetCurrentThread(t);
+  t->Init();
   return t->ThreadStart();
 }
 

compiler-rt/lib/dfsan/dfsan_thread.cpp

@@ -67,8 +67,6 @@ void DFsanThread::Destroy() {
 }
 
 thread_return_t DFsanThread::ThreadStart() {
-  Init();
-
   if (!start_routine_) {
     // start_routine_ == 0 if we're on the main thread or on one of the
     // OS X libdispatch worker threads. But nobody is supposed to call