Re: [tj-wq:for-7.1 14/18] kernel/workqueue.c:8289:34: warning: array subscript 1 is above array bounds of 'int[1]'

[Breno Leitao <leitao@debian.org>]

On Fri, Apr 03, 2026 at 04:42:14PM +0800, kernel test robot wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/tj/wq.git for-7.1
> head:   41e3ccca00b374b7f39cf68e818b59a921cd7069
> commit: 5920d046f7ae3bf9cf51b9d915c1fff13d299d84 [14/18] workqueue: add WQ_AFFN_CACHE_SHARD affinity scope
> config: nios2-randconfig-001-20260402 (https://download.01.org/0day-ci/archive/20260402/202604022343.GQtkF2vO-lkp@intel.com/config)
> compiler: nios2-linux-gcc (GCC) 8.5.0
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260402/202604022343.GQtkF2vO-lkp@intel.com/reproduce)
> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202604022343.GQtkF2vO-lkp@intel.com/
> 
> All warnings (new ones prefixed by >>):
> 
>    kernel/workqueue.c: In function 'workqueue_init_topology':
> >> kernel/workqueue.c:8289:34: warning: array subscript 1 is above array bounds of 'int[1]' [-Warray-bounds]
>        cpu_shard_id[c] = cpu_shard_id[cpumask_first(sibling_cpus)];
>                          ~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~

I can finally reproduce it. This is related to nios2 having NR_CPU=1.

	In function ‘llc_populate_cpu_shard_id’,
	inlined from ‘precompute_cache_shard_ids’ at /home/leit/Devel/linux-next/kernel/workqueue.c:8321:3,
	inlined from ‘workqueue_init_topology’ at /home/leit/Devel/linux-next/kernel/workqueue.c:8354:2:
	/home/leit/Devel/linux-next/kernel/workqueue.c:8289:55: warning: array subscript 1 is above array bounds of ‘int[1]’ [-Warray-bounds]
	8289 |                         cpu_shard_id[c] = cpu_shard_id[cpumask_first(sibling_cpus)];
	|                                           ~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	/home/leit/Devel/linux-next/kernel/workqueue.c: In function ‘workqueue_init_topology’:
	/home/leit/Devel/linux-next/kernel/workqueue.c:8171:12: note: while referencing ‘cpu_shard_id’
	8171 | static int cpu_shard_id[NR_CPUS] __initdata;
	|            ^~~~~~~~~~~~
	make[1]: Leaving directory '/tmp/wq-nios2'


Working on a fix,

Thanks for the report, dear robot :-)
--breno