Re: [PATCH v3 3/3] md: protect md_thread with rcu

[kernel test robot <lkp@intel.com>]

Hi Yu,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on song-md/md-next]
[also build test WARNING on device-mapper-dm/for-next linus/master v6.3-rc4 next-20230330]
[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#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Yu-Kuai/md-pass-a-md_thread-pointer-to-md_register_thread/20230330-202251
base:   git://git.kernel.org/pub/scm/linux/kernel/git/song/md.git md-next
patch link:    https://lore.kernel.org/r/20230330202046.795213-4-yukuai1%40huaweicloud.com
patch subject: [PATCH v3 3/3] md: protect md_thread with rcu
config: x86_64-randconfig-s023 (https://download.01.org/0day-ci/archive/20230331/202303310252.5OJzxk7h-lkp@intel.com/config)
compiler: gcc-11 (Debian 11.3.0-8) 11.3.0
reproduce:
        # apt-get install sparse
        # sparse version: v0.6.4-39-gce1a6720-dirty
        # https://github.com/intel-lab-lkp/linux/commit/b6edd339e54dc14576816f285b99e0e1815ed1e0
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Yu-Kuai/md-pass-a-md_thread-pointer-to-md_register_thread/20230330-202251
        git checkout b6edd339e54dc14576816f285b99e0e1815ed1e0
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=x86_64 olddefconfig
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=x86_64 SHELL=/bin/bash drivers/md/

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
| Link: https://lore.kernel.org/oe-kbuild-all/202303310252.5OJzxk7h-lkp@intel.com/

sparse warnings: (new ones prefixed by >>)
>> drivers/md/md.c:7905:18: sparse: sparse: incompatible types in comparison expression (different address spaces):
>> drivers/md/md.c:7905:18: sparse:    struct md_thread [noderef] __rcu *
>> drivers/md/md.c:7905:18: sparse:    struct md_thread *
   drivers/md/md.c:7939:9: sparse: sparse: incompatible types in comparison expression (different address spaces):
   drivers/md/md.c:7939:9: sparse:    struct md_thread [noderef] __rcu *
   drivers/md/md.c:7939:9: sparse:    struct md_thread *
   drivers/md/md.c:7952:9: sparse: sparse: incompatible types in comparison expression (different address spaces):
   drivers/md/md.c:7952:9: sparse:    struct md_thread [noderef] __rcu *
   drivers/md/md.c:7952:9: sparse:    struct md_thread *

vim +7905 drivers/md/md.c

  7899	
  7900	void md_wakeup_thread(struct md_thread **threadp)
  7901	{
  7902		struct md_thread *thread;
  7903	
  7904		rcu_read_lock();
> 7905		thread = rcu_dereference(*threadp);
  7906		if (thread) {
  7907			pr_debug("md: waking up MD thread %s.\n", thread->tsk->comm);
  7908			set_bit(THREAD_WAKEUP, &thread->flags);
  7909			wake_up(&thread->wqueue);
  7910		}
  7911		rcu_read_unlock();
  7912	}
  7913	EXPORT_SYMBOL(md_wakeup_thread);
  7914	

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