Hi Eric, FYI, the error/warning still remains. tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master head: c11d28ab4a691736e30b49813fb801847bd44e83 commit: 2b195850128f5bafde177b12489d9fa27962cc1e [5095/12102] tcp: add tp->dup_ack_counter config: x86_64-randconfig-a002-20200524 (attached as .config) compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project 3393cc4cebf9969db94dc424b7a2b6195589c33b) 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 git checkout 2b195850128f5bafde177b12489d9fa27962cc1e # 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: kbuild test robot <lkp(a)intel.com&gt; All warnings (new ones prefixed by >>, old ones prefixed by <<): NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPACKCOMPRESSED, ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ include/net/ip.h:293:41: note: expanded from macro 'NET_ADD_STATS' #define NET_ADD_STATS(net, field, adnd) SNMP_ADD_STATS((net)->mib.net_statistics, field, adnd) ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ include/net/snmp.h:143:4: note: expanded from macro 'SNMP_ADD_STATS' this_cpu_add(mib->mibs[field], addend) ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ include/linux/percpu-defs.h:509:33: note: expanded from macro 'this_cpu_add' #define this_cpu_add(pcp, val) __pcpu_size_call(this_cpu_add_, pcp, val) ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ note: (skipping 1 expansions in backtrace; use -fmacro-backtrace-limit=0 to see all) <scratch space>:160:1: note: expanded from here this_cpu_add_8 ^ arch/x86/include/asm/percpu.h:492:35: note: expanded from macro 'this_cpu_add_8' #define this_cpu_add_8(pcp, val) percpu_add_op(volatile, (pcp), val) ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ arch/x86/include/asm/percpu.h:131:31: note: expanded from macro 'percpu_add_op' ((val) == 1 || (val) == -1)) ? ~~~~~ ^ ~~ 1 warning generated. vim +188 net/ipv4/tcp_output.c ^1da177e4c3f41 Linus Torvalds 2005-04-16 180 67edfef7863957 Andi Kleen 2009-07-21 181 /* Account for an ACK we sent. */ 27cde44a259c38 Yuchung Cheng 2018-07-18 182 static inline void tcp_event_ack_sent(struct sock *sk, unsigned int pkts, 27cde44a259c38 Yuchung Cheng 2018-07-18 183 u32 rcv_nxt) ^1da177e4c3f41 Linus Torvalds 2005-04-16 184 { 5d9f4262b7ea41 Eric Dumazet 2018-05-17 185 struct tcp_sock *tp = tcp_sk(sk); 5d9f4262b7ea41 Eric Dumazet 2018-05-17 186 2b195850128f5b Eric Dumazet 2020-04-30 187 if (unlikely(tp->compressed_ack)) { 200d95f4575934 Eric Dumazet 2018-05-17 @188 NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPACKCOMPRESSED, 2b195850128f5b Eric Dumazet 2020-04-30 189 tp->compressed_ack); 2b195850128f5b Eric Dumazet 2020-04-30 190 tp->compressed_ack = 0; 5d9f4262b7ea41 Eric Dumazet 2018-05-17 191 if (hrtimer_try_to_cancel(&tp->compressed_ack_timer) == 1) 5d9f4262b7ea41 Eric Dumazet 2018-05-17 192 __sock_put(sk); 5d9f4262b7ea41 Eric Dumazet 2018-05-17 193 } 27cde44a259c38 Yuchung Cheng 2018-07-18 194 27cde44a259c38 Yuchung Cheng 2018-07-18 195 if (unlikely(rcv_nxt != tp->rcv_nxt)) 27cde44a259c38 Yuchung Cheng 2018-07-18 196 return; /* Special ACK sent by DCTCP to reflect ECN */ 463c84b97f2401 Arnaldo Carvalho de Melo 2005-08-09 197 tcp_dec_quickack_mode(sk, pkts); 463c84b97f2401 Arnaldo Carvalho de Melo 2005-08-09 198 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK); ^1da177e4c3f41 Linus Torvalds 2005-04-16 199 } ^1da177e4c3f41 Linus Torvalds 2005-04-16 200 :::::: The code at line 188 was first introduced by commit :::::: 200d95f4575934e49f872109cce18c5e72383eb8 tcp: add TCPAckCompressed SNMP counter :::::: TO: Eric Dumazet <edumazet(a)google.com&gt; :::::: CC: David S. Miller <davem(a)davemloft.net&gt; --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org