tree:   https://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git linux-5.14.y-rt-rebase
head:   1dd417d8628a02944d12964253beb7ab2773c93e
commit: e7d6f3b2ba81e813e19e32c7fbdd2f14b56f29f8 [53/239] mm: slub: Move flush_cpu_slab() invocations __free_slab() invocations out of IRQ context
config: arm-randconfig-r024-20210809 (attached as .config)
compiler: arm-linux-gnueabi-gcc (GCC) 10.3.0
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
        # https://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git/commit/?id=e7d6f3b2ba81e813e19e32c7fbdd2f14b56f29f8
        git remote add linux-rt-devel https://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git
        git fetch --no-tags linux-rt-devel linux-5.14.y-rt-rebase
        git checkout e7d6f3b2ba81e813e19e32c7fbdd2f14b56f29f8
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-10.3.0 make.cross ARCH=arm 

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

All warnings (new ones prefixed by >>):

>> mm/slub.c:4396:5: warning: no previous prototype for '__kmem_cache_do_shrink' [-Wmissing-prototypes]
    4396 | int __kmem_cache_do_shrink(struct kmem_cache *s)
         |     ^~~~~~~~~~~~~~~~~~~~~~


vim +/__kmem_cache_do_shrink +4396 mm/slub.c

  4386	
  4387	/*
  4388	 * kmem_cache_shrink discards empty slabs and promotes the slabs filled
  4389	 * up most to the head of the partial lists. New allocations will then
  4390	 * fill those up and thus they can be removed from the partial lists.
  4391	 *
  4392	 * The slabs with the least items are placed last. This results in them
  4393	 * being allocated from last increasing the chance that the last objects
  4394	 * are freed in them.
  4395	 */
> 4396	int __kmem_cache_do_shrink(struct kmem_cache *s)
  4397	{
  4398		int node;
  4399		int i;
  4400		struct kmem_cache_node *n;
  4401		struct page *page;
  4402		struct page *t;
  4403		struct list_head discard;
  4404		struct list_head promote[SHRINK_PROMOTE_MAX];
  4405		unsigned long flags;
  4406		int ret = 0;
  4407	
  4408		for_each_kmem_cache_node(s, node, n) {
  4409			INIT_LIST_HEAD(&discard);
  4410			for (i = 0; i < SHRINK_PROMOTE_MAX; i++)
  4411				INIT_LIST_HEAD(promote + i);
  4412	
  4413			spin_lock_irqsave(&n->list_lock, flags);
  4414	
  4415			/*
  4416			 * Build lists of slabs to discard or promote.
  4417			 *
  4418			 * Note that concurrent frees may occur while we hold the
  4419			 * list_lock. page->inuse here is the upper limit.
  4420			 */
  4421			list_for_each_entry_safe(page, t, &n->partial, slab_list) {
  4422				int free = page->objects - page->inuse;
  4423	
  4424				/* Do not reread page->inuse */
  4425				barrier();
  4426	
  4427				/* We do not keep full slabs on the list */
  4428				BUG_ON(free <= 0);
  4429	
  4430				if (free == page->objects) {
  4431					list_move(&page->slab_list, &discard);
  4432					n->nr_partial--;
  4433				} else if (free <= SHRINK_PROMOTE_MAX)
  4434					list_move(&page->slab_list, promote + free - 1);
  4435			}
  4436	
  4437			/*
  4438			 * Promote the slabs filled up most to the head of the
  4439			 * partial list.
  4440			 */
  4441			for (i = SHRINK_PROMOTE_MAX - 1; i >= 0; i--)
  4442				list_splice(promote + i, &n->partial);
  4443	
  4444			spin_unlock_irqrestore(&n->list_lock, flags);
  4445	
  4446			/* Release empty slabs */
  4447			list_for_each_entry_safe(page, t, &discard, slab_list)
  4448				discard_slab(s, page);
  4449	
  4450			if (slabs_node(s, node))
  4451				ret = 1;
  4452		}
  4453	
  4454		return ret;
  4455	}
  4456	

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