We should ifdef check the define of _GNU_SOURCE
diff --git a/src/core/support/cpu_linux.c b/src/core/support/cpu_linux.c
index 508ebfa..e0df699 100644
--- a/src/core/support/cpu_linux.c
+++ b/src/core/support/cpu_linux.c
@@ -31,7 +31,9 @@
  *
  */
 
+#ifndef _GNU_SOURCE
 #define _GNU_SOURCE
+#undef  /* _GNU_SOURCE */
 
 #include <grpc/support/port_platform.h>