tree: https://github.com/congwang/linux.git sockmap-lock head: 551798d69f730a6ceac704e5c13df8e8a0e88685 commit: 551798d69f730a6ceac704e5c13df8e8a0e88685 [5/5] net: remove skb_send_sock_locked() config: x86_64-randconfig-a006-20210309 (attached as .config) compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project cd9a69289c7825d54450cb6829fef2c8e0f1963a) reproduce (this is a W=1 build): wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross # install x86_64 cross compiling tool for clang build # apt-get install binutils-x86-64-linux-gnu # https://github.com/congwang/linux/commit/551798d69f730a6ceac704e5c13df8e8... git remote add congwang https://github.com/congwang/linux.git git fetch --no-tags congwang sockmap-lock git checkout 551798d69f730a6ceac704e5c13df8e8a0e88685 # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=x86_64 If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All warnings (new ones prefixed by >>): int skb_send_sock(struct sock *sk, struct sk_buff *skb, int offset, int len) ^ net/core/skbuff.c:2611:1: note: declare 'static' if the function is not intended to be used outside of this translation unit int skb_send_sock(struct sock *sk, struct sk_buff *skb, int offset, int len) ^ static 1 warning generated. vim +/skb_send_sock +2611 net/core/skbuff.c f7c687a4b2bc9e Cong Wang 2021-03-09 2609 f7c687a4b2bc9e Cong Wang 2021-03-09 2610 /* Send skb data on a socket. Socket must be unlocked. */ f7c687a4b2bc9e Cong Wang 2021-03-09 @2611 int skb_send_sock(struct sock *sk, struct sk_buff *skb, int offset, int len) f7c687a4b2bc9e Cong Wang 2021-03-09 2612 { f7c687a4b2bc9e Cong Wang 2021-03-09 2613 return __skb_send_sock(sk, skb, offset, len, sendmsg_unlocked, f7c687a4b2bc9e Cong Wang 2021-03-09 2614 sendpage_unlocked); f7c687a4b2bc9e Cong Wang 2021-03-09 2615 } f7c687a4b2bc9e Cong Wang 2021-03-09 2616 :::::: The code at line 2611 was first introduced by commit :::::: f7c687a4b2bc9ea20381ca5312fab026017f581c skmsg: introduce skb_send_sock() :::::: TO: Cong Wang <cong.wang(a)bytedance.com&gt; :::::: CC: Cong Wang <cong.wang(a)bytedance.com&gt; --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org