diff --git a/compiler-rt/lib/memprof/memprof_rtl.cpp b/compiler-rt/lib/memprof/memprof_rtl.cpp
--- a/compiler-rt/lib/memprof/memprof_rtl.cpp
+++ b/compiler-rt/lib/memprof/memprof_rtl.cpp
@@ -26,6 +26,7 @@
 #include "sanitizer_common/sanitizer_symbolizer.h"
 
 #include <time.h>
+#include <unistd.h>
 
 uptr __memprof_shadow_memory_dynamic_address; // Global interface symbol.
 
@@ -39,6 +40,7 @@
   if (atomic_fetch_add(&num_calls, 1, memory_order_relaxed) != 0) {
     // Don't die twice - run a busy loop.
     while (1) {
+      pause();
     }
   }
   if (common_flags()->print_module_map >= 1)