diff --git a/compiler-rt/lib/tsan/rtl/tsan_platform_mac.cpp b/compiler-rt/lib/tsan/rtl/tsan_platform_mac.cpp
--- a/compiler-rt/lib/tsan/rtl/tsan_platform_mac.cpp
+++ b/compiler-rt/lib/tsan/rtl/tsan_platform_mac.cpp
@@ -76,16 +76,19 @@
 ALIGNED(64) static char main_thread_state[sizeof(ThreadState)];
 static ThreadState *main_thread_state_loc = (ThreadState *)main_thread_state;
 
+static ThreadState **thread_location(uptr thread_identity) {
+  if (thread_identity == main_thread_identity)
+    return &main_thread_state_loc;
+  return (ThreadState **)MemToShadow(thread_identity);
+}
+
 // We cannot use pthread_self() before libpthread has been initialized.  Our
 // current heuristic for guarding this is checking `main_thread_identity` which
 // is only assigned in `__tsan::InitializePlatform`.
 static ThreadState **cur_thread_location() {
   if (main_thread_identity == 0)
     return &main_thread_state_loc;
-  uptr thread_identity = (uptr)pthread_self();
-  if (thread_identity == main_thread_identity)
-    return &main_thread_state_loc;
-  return (ThreadState **)MemToShadow(thread_identity);
+  return thread_location((uptr)pthread_self());
 }
 
 ThreadState *cur_thread() {
@@ -209,6 +212,10 @@
 static void my_pthread_introspection_hook(unsigned int event, pthread_t thread,
                                           void *addr, size_t size) {
   if (event == PTHREAD_INTROSPECTION_THREAD_CREATE) {
+    CHECK_NE(thread, main_thread_identity);
+    // Reset ThreadState pointer in shadow memory which could contain non-zero
+    // bytes from unobserved operations (e.g., IOKit).
+    *thread_location((uptr)thread) = nullptr;
     if (thread == pthread_self()) {
       // The current thread is a newly created GCD worker thread.
       ThreadState *thr = cur_thread();