tree: https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git dev.2020.12.15b head: f895a17eec290b0038a6294d884a9cc92d7d6e80 commit: 892f898ac8cfffe89e3c7fd483c8eaf71b3f12aa [128/134] rcutorture: Test runtime toggling of CPUs' callback offloading config: x86_64-rhel (attached as .config) compiler: gcc-9 (Debian 9.3.0-15) 9.3.0 reproduce (this is a W=1 build): # https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git/com... git remote add rcu https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git git fetch --no-tags rcu dev.2020.12.15b git checkout 892f898ac8cfffe89e3c7fd483c8eaf71b3f12aa # save the attached .config to linux build tree make W=1 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 errors (new ones prefixed by >>, old ones prefixed by <<): >> ERROR: modpost: "rcu_nocb_cpu_deoffload" [kernel/rcu/rcutorture.ko] undefined!