Re: [PATCH v3 4/4] arm64: Kconfig: Enable HOTPLUG_SMT

[kernel test robot <yujie.liu@intel.com>]

Hi Yicong,

kernel test robot noticed the following build errors:

[auto build test ERROR on arm64/for-next/core]
[also build test ERROR on driver-core/driver-core-testing driver-core/driver-core-next driver-core/driver-core-linus arm/for-next kvmarm/next soc/for-next linus/master arm/fixes v6.7-rc1 next-20231115]
[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/Yicong-Yang/arch_topology-Support-basic-SMT-control-for-the-driver/20231114-120544
base:   https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-next/core
patch link:    https://lore.kernel.org/r/20231114040110.54590-5-yangyicong%40huawei.com
patch subject: [PATCH v3 4/4] arm64: Kconfig: Enable HOTPLUG_SMT
config: arm64-randconfig-002-20231115 (https://download.01.org/0day-ci/archive/20231115/202311151900.K9xc6Xqz-lkp@intel.com/config)
compiler: aarch64-linux-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231115/202311151900.K9xc6Xqz-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 <yujie.liu@intel.com>
| Closes: https://lore.kernel.org/r/202311151900.K9xc6Xqz-lkp@intel.com/

All errors (new ones prefixed by >>):

   kernel/cpu.c: In function 'cpuhp_smt_disable':
>> kernel/cpu.c:2687:23: error: implicit declaration of function 'cpu_down_maps_locked' [-Werror=implicit-function-declaration]
    2687 |                 ret = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
         |                       ^~~~~~~~~~~~~~~~~~~~
   cc1: some warnings being treated as errors


vim +/cpu_down_maps_locked +2687 kernel/cpu.c

dc8d37ed304eee Arnd Bergmann    2019-12-10  2672  
dc8d37ed304eee Arnd Bergmann    2019-12-10  2673  int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval)
dc8d37ed304eee Arnd Bergmann    2019-12-10  2674  {
dc8d37ed304eee Arnd Bergmann    2019-12-10  2675  	int cpu, ret = 0;
dc8d37ed304eee Arnd Bergmann    2019-12-10  2676  
dc8d37ed304eee Arnd Bergmann    2019-12-10  2677  	cpu_maps_update_begin();
dc8d37ed304eee Arnd Bergmann    2019-12-10  2678  	for_each_online_cpu(cpu) {
dc8d37ed304eee Arnd Bergmann    2019-12-10  2679  		if (topology_is_primary_thread(cpu))
dc8d37ed304eee Arnd Bergmann    2019-12-10  2680  			continue;
38253464bc821d Michael Ellerman 2023-07-05  2681  		/*
38253464bc821d Michael Ellerman 2023-07-05  2682  		 * Disable can be called with CPU_SMT_ENABLED when changing
38253464bc821d Michael Ellerman 2023-07-05  2683  		 * from a higher to lower number of SMT threads per core.
38253464bc821d Michael Ellerman 2023-07-05  2684  		 */
38253464bc821d Michael Ellerman 2023-07-05  2685  		if (ctrlval == CPU_SMT_ENABLED && cpu_smt_thread_allowed(cpu))
38253464bc821d Michael Ellerman 2023-07-05  2686  			continue;
dc8d37ed304eee Arnd Bergmann    2019-12-10 @2687  		ret = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
dc8d37ed304eee Arnd Bergmann    2019-12-10  2688  		if (ret)
dc8d37ed304eee Arnd Bergmann    2019-12-10  2689  			break;
dc8d37ed304eee Arnd Bergmann    2019-12-10  2690  		/*
dc8d37ed304eee Arnd Bergmann    2019-12-10  2691  		 * As this needs to hold the cpu maps lock it's impossible
dc8d37ed304eee Arnd Bergmann    2019-12-10  2692  		 * to call device_offline() because that ends up calling
dc8d37ed304eee Arnd Bergmann    2019-12-10  2693  		 * cpu_down() which takes cpu maps lock. cpu maps lock
dc8d37ed304eee Arnd Bergmann    2019-12-10  2694  		 * needs to be held as this might race against in kernel
dc8d37ed304eee Arnd Bergmann    2019-12-10  2695  		 * abusers of the hotplug machinery (thermal management).
dc8d37ed304eee Arnd Bergmann    2019-12-10  2696  		 *
dc8d37ed304eee Arnd Bergmann    2019-12-10  2697  		 * So nothing would update device:offline state. That would
dc8d37ed304eee Arnd Bergmann    2019-12-10  2698  		 * leave the sysfs entry stale and prevent onlining after
dc8d37ed304eee Arnd Bergmann    2019-12-10  2699  		 * smt control has been changed to 'off' again. This is
dc8d37ed304eee Arnd Bergmann    2019-12-10  2700  		 * called under the sysfs hotplug lock, so it is properly
dc8d37ed304eee Arnd Bergmann    2019-12-10  2701  		 * serialized against the regular offline usage.
dc8d37ed304eee Arnd Bergmann    2019-12-10  2702  		 */
dc8d37ed304eee Arnd Bergmann    2019-12-10  2703  		cpuhp_offline_cpu_device(cpu);
dc8d37ed304eee Arnd Bergmann    2019-12-10  2704  	}
dc8d37ed304eee Arnd Bergmann    2019-12-10  2705  	if (!ret)
dc8d37ed304eee Arnd Bergmann    2019-12-10  2706  		cpu_smt_control = ctrlval;
dc8d37ed304eee Arnd Bergmann    2019-12-10  2707  	cpu_maps_update_done();
dc8d37ed304eee Arnd Bergmann    2019-12-10  2708  	return ret;
dc8d37ed304eee Arnd Bergmann    2019-12-10  2709  }
dc8d37ed304eee Arnd Bergmann    2019-12-10  2710  

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