reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/jfern/linux.git/commit/?id=720e9973f06adae235ae751d9b2ee1acf81fe98a
        git remote add jfern https://git.kernel.org/pub/scm/linux/kernel/git/jfern/linux.git
        git fetch --no-tags jfern rcu/irq-exit-v2-no-task
        git checkout 720e9973f06adae235ae751d9b2ee1acf81fe98a
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=i386 olddefconfig
        make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash kernel/