tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master head: 4b6c093e21d36bede0fd88fd0aeb3b03647260e4 commit: 670d0a4b10704667765f7d18f7592993d02783aa sparse: use identifiers to define address spaces date: 8 weeks ago config: s390-randconfig-s032-20200811 (attached as .config) compiler: s390-linux-gcc (GCC) 9.3.0 reproduce: wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross # apt-get install sparse # sparse version: v0.6.2-168-g9554805c-dirty git checkout 670d0a4b10704667765f7d18f7592993d02783aa # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' ARCH=s390 If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; sparse warnings: (new ones prefixed by >>) net/ipv4/tcp_cong.c:228:24: sparse: got struct tcp_congestion_ops *[assigned] ca net/ipv4/tcp_cong.c:228:22: sparse: sparse: incorrect type in assignment (different address spaces) @@ expected struct tcp_congestion_ops const *prev @@ got struct tcp_congestion_ops const [noderef] __rcu *[assigned] __old @@ net/ipv4/tcp_cong.c:228:22: sparse: expected struct tcp_congestion_ops const *prev net/ipv4/tcp_cong.c:228:22: sparse: got struct tcp_congestion_ops const [noderef] __rcu *[assigned] __old vim +228 net/ipv4/tcp_cong.c 317a76f9a44b437 Stephen Hemminger 2005-06-23 213 317a76f9a44b437 Stephen Hemminger 2005-06-23 214 /* Used by sysctl to change default congestion control */ 6670e152447732b Stephen Hemminger 2017-11-14 215 int tcp_set_default_congestion_control(struct net *net, const char *name) 317a76f9a44b437 Stephen Hemminger 2005-06-23 216 { 317a76f9a44b437 Stephen Hemminger 2005-06-23 217 struct tcp_congestion_ops *ca; 6670e152447732b Stephen Hemminger 2017-11-14 218 const struct tcp_congestion_ops *prev; 6670e152447732b Stephen Hemminger 2017-11-14 219 int ret; 317a76f9a44b437 Stephen Hemminger 2005-06-23 220 6670e152447732b Stephen Hemminger 2017-11-14 221 rcu_read_lock(); 6670e152447732b Stephen Hemminger 2017-11-14 222 ca = tcp_ca_find_autoload(net, name); 6670e152447732b Stephen Hemminger 2017-11-14 223 if (!ca) { 6670e152447732b Stephen Hemminger 2017-11-14 224 ret = -ENOENT; 0baf26b0fcd74bb Martin KaFai Lau 2020-01-08 225 } else if (!bpf_try_module_get(ca, ca->owner)) { 6670e152447732b Stephen Hemminger 2017-11-14 226 ret = -EBUSY; 6670e152447732b Stephen Hemminger 2017-11-14 227 } else { 6670e152447732b Stephen Hemminger 2017-11-14 @228 prev = xchg(&net->ipv4.tcp_congestion_control, ca); 6670e152447732b Stephen Hemminger 2017-11-14 229 if (prev) 0baf26b0fcd74bb Martin KaFai Lau 2020-01-08 230 bpf_module_put(prev, prev->owner); 317a76f9a44b437 Stephen Hemminger 2005-06-23 231 6670e152447732b Stephen Hemminger 2017-11-14 232 ca->flags |= TCP_CONG_NON_RESTRICTED; 317a76f9a44b437 Stephen Hemminger 2005-06-23 233 ret = 0; 317a76f9a44b437 Stephen Hemminger 2005-06-23 234 } 6670e152447732b Stephen Hemminger 2017-11-14 235 rcu_read_unlock(); 317a76f9a44b437 Stephen Hemminger 2005-06-23 236 317a76f9a44b437 Stephen Hemminger 2005-06-23 237 return ret; 317a76f9a44b437 Stephen Hemminger 2005-06-23 238 } 317a76f9a44b437 Stephen Hemminger 2005-06-23 239 :::::: The code at line 228 was first introduced by commit :::::: 6670e152447732ba90626f36dfc015a13fbf150e tcp: Namespace-ify sysctl_tcp_default_congestion_control :::::: TO: Stephen Hemminger <stephen(a)networkplumber.org&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