Index: lib/tsan/rtl/tsan_interceptors.cc
===================================================================
--- lib/tsan/rtl/tsan_interceptors.cc
+++ lib/tsan/rtl/tsan_interceptors.cc
@@ -974,6 +974,9 @@
 TSAN_INTERCEPTOR(int, pthread_create,
     void *th, void *attr, void *(*callback)(void*), void * param) {
   SCOPED_INTERCEPTOR_RAW(pthread_create, th, attr, callback, param);
+
+  MaybeSpawnBackgroundThread();
+
   if (ctx->after_multithreaded_fork) {
     if (flags()->die_after_fork) {
       Report("ThreadSanitizer: starting new threads after multi-threaded "
Index: lib/tsan/rtl/tsan_rtl.h
===================================================================
--- lib/tsan/rtl/tsan_rtl.h
+++ lib/tsan/rtl/tsan_rtl.h
@@ -700,6 +700,7 @@
 void PrintCurrentStackSlow(uptr pc);  // uses libunwind
 
 void Initialize(ThreadState *thr);
+void MaybeSpawnBackgroundThread();
 int Finalize(ThreadState *thr);
 
 void OnUserAlloc(ThreadState *thr, uptr pc, uptr p, uptr sz, bool write);
Index: lib/tsan/rtl/tsan_rtl.cc
===================================================================
--- lib/tsan/rtl/tsan_rtl.cc
+++ lib/tsan/rtl/tsan_rtl.cc
@@ -384,13 +384,6 @@
 #if !SANITIZER_GO
   InitializeLibIgnore();
   Symbolizer::GetOrInit()->AddHooks(EnterSymbolizer, ExitSymbolizer);
-  // On MIPS, TSan initialization is run before
-  // __pthread_initialize_minimal_internal() is finished, so we can not spawn
-  // new threads.
-#ifndef __mips__
-  StartBackgroundThread();
-  SetSandboxingCallback(StopBackgroundThread);
-#endif
 #endif
 
   VPrintf(1, "***** Running under ThreadSanitizer v2 (pid %d) *****\n",
@@ -419,6 +412,21 @@
   OnInitialize();
 }
 
+void MaybeSpawnBackgroundThread() {
+  // On MIPS, TSan initialization is run before
+  // __pthread_initialize_minimal_internal() is finished, so we can not spawn
+  // new threads.
+#if !SANITIZER_GO && !defined(__mips__)
+  static atomic_uint32_t bg_thread = {};
+  if (atomic_load(&bg_thread, memory_order_relaxed) == 0 &&
+      atomic_exchange(&bg_thread, 1, memory_order_relaxed) == 0) {
+    StartBackgroundThread();
+    SetSandboxingCallback(StopBackgroundThread);
+  }
+#endif
+}
+
+
 int Finalize(ThreadState *thr) {
   bool failed = false;