Hi Frederic,

I love your patch! Yet something to improve:

[auto build test ERROR on rcu/dev]
[also build test ERROR on rcu/rcu/next next-20201113]
[cannot apply to tip/timers/core linus/master linux/master v5.10-rc3]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Frederic-Weisbecker/rcu-nocb-De-offload-and-re-offload-support-v4/20201113-201658
base:   https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git dev
config: arm-randconfig-r013-20201113 (attached as .config)
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project 9e0c35655b6e8186baef8840b26ba4090503b554)
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 arm cross compiling tool for clang build
        # apt-get install binutils-arm-linux-gnueabi
        # https://github.com/0day-ci/linux/commit/4c0d56c4bf8ec775e46d5e895080a2df42e306d8
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Frederic-Weisbecker/rcu-nocb-De-offload-and-re-offload-support-v4/20201113-201658
        git checkout 4c0d56c4bf8ec775e46d5e895080a2df42e306d8
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=arm 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   In file included from kernel/rcu/tree.c:4591:
>> kernel/rcu/tree_plugin.h:71:40: error: implicit declaration of function 'lockdep_is_cpus_held' [-Werror,-Wimplicit-function-declaration]
                     (IS_ENABLED(CONFIG_HOTPLUG_CPU) && lockdep_is_cpus_held()) ||
                                                        ^
   kernel/rcu/tree_plugin.h:71:40: note: did you mean 'lockdep_assert_cpus_held'?
   include/linux/cpu.h:136:20: note: 'lockdep_assert_cpus_held' declared here
   static inline void lockdep_assert_cpus_held(void) { }
                      ^
   1 error generated.

vim +/lockdep_is_cpus_held +71 kernel/rcu/tree_plugin.h

    57	
    58	static bool rcu_rdp_is_offloaded(struct rcu_data *rdp)
    59	{
    60		/*
    61		 * In order to read the offloaded state of an rdp is a safe
    62		 * and stable way and prevent from its value to be changed
    63		 * under us, we must either hold the barrier mutex, the cpu
    64		 * hotplug lock (read or write) or the nocb lock. Local
    65		 * non-preemptible reads are also safe. NOCB kthreads and
    66		 * timers have their own means of synchronization against the
    67		 * offloaded state updaters.
    68		 */
    69		RCU_LOCKDEP_WARN(
    70			!(lockdep_is_held(&rcu_state.barrier_mutex) ||
  > 71			  (IS_ENABLED(CONFIG_HOTPLUG_CPU) && lockdep_is_cpus_held()) ||
    72			  rcu_lockdep_is_held_nocb(rdp) ||
    73			  (rdp == this_cpu_ptr(&rcu_data) &&
    74			   !(IS_ENABLED(CONFIG_PREEMPT_COUNT) && preemptible())) ||
    75			  rcu_current_is_nocb_kthread(rdp) ||
    76			  rcu_running_nocb_timer(rdp)),
    77			"Unsafe read of RCU_NOCB offloaded state"
    78		);
    79	
    80		return rcu_segcblist_is_offloaded(&rdp->cblist);
    81	}
    82	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all(a)lists.01.org