kernel/cpu.c:2681:9: error: call to undeclared function 'cpu_down_maps_locked'; ISO C99 and later do not support implicit function declarations

kernel/cpu.c:2681:9: error: call to undeclared function 'cpu_down_maps_locked'; ISO C99 and later do not support implicit function declarations

[kernel test robot]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   72761a7e31225971d0b29d9195e0ffa986b77867
commit: 76c43eb507bc1162850fdae6cc44790d1c9a83ea MIPS: SMP: Implement parallel CPU bring up for EyeQ
date:   6 months ago
config: mips-randconfig-r122-20251026 (https://download.01.org/0day-ci/archive/20251027/202510270120.21wA1aX1-lkp@intel.com/config)
compiler: clang version 22.0.0git (https://github.com/llvm/llvm-project e1ae12640102fd2b05bc567243580f90acb1135f)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251027/202510270120.21wA1aX1-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/202510270120.21wA1aX1-lkp@intel.com/

All errors (new ones prefixed by >>):

>> kernel/cpu.c:2681:9: error: call to undeclared function 'cpu_down_maps_locked'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
    2681 |                 ret = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
         |                       ^
   1 error generated.


vim +/cpu_down_maps_locked +2681 kernel/cpu.c

dc8d37ed304eee Arnd Bergmann    2019-12-10  2666  
dc8d37ed304eee Arnd Bergmann    2019-12-10  2667  int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval)
dc8d37ed304eee Arnd Bergmann    2019-12-10  2668  {
dc8d37ed304eee Arnd Bergmann    2019-12-10  2669  	int cpu, ret = 0;
dc8d37ed304eee Arnd Bergmann    2019-12-10  2670  
dc8d37ed304eee Arnd Bergmann    2019-12-10  2671  	cpu_maps_update_begin();
dc8d37ed304eee Arnd Bergmann    2019-12-10  2672  	for_each_online_cpu(cpu) {
dc8d37ed304eee Arnd Bergmann    2019-12-10  2673  		if (topology_is_primary_thread(cpu))
dc8d37ed304eee Arnd Bergmann    2019-12-10  2674  			continue;
38253464bc821d Michael Ellerman 2023-07-05  2675  		/*
38253464bc821d Michael Ellerman 2023-07-05  2676  		 * Disable can be called with CPU_SMT_ENABLED when changing
38253464bc821d Michael Ellerman 2023-07-05  2677  		 * from a higher to lower number of SMT threads per core.
38253464bc821d Michael Ellerman 2023-07-05  2678  		 */
38253464bc821d Michael Ellerman 2023-07-05  2679  		if (ctrlval == CPU_SMT_ENABLED && cpu_smt_thread_allowed(cpu))
38253464bc821d Michael Ellerman 2023-07-05  2680  			continue;
dc8d37ed304eee Arnd Bergmann    2019-12-10 @2681  		ret = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
dc8d37ed304eee Arnd Bergmann    2019-12-10  2682  		if (ret)
dc8d37ed304eee Arnd Bergmann    2019-12-10  2683  			break;
dc8d37ed304eee Arnd Bergmann    2019-12-10  2684  		/*
dc8d37ed304eee Arnd Bergmann    2019-12-10  2685  		 * As this needs to hold the cpu maps lock it's impossible
dc8d37ed304eee Arnd Bergmann    2019-12-10  2686  		 * to call device_offline() because that ends up calling
dc8d37ed304eee Arnd Bergmann    2019-12-10  2687  		 * cpu_down() which takes cpu maps lock. cpu maps lock
dc8d37ed304eee Arnd Bergmann    2019-12-10  2688  		 * needs to be held as this might race against in kernel
dc8d37ed304eee Arnd Bergmann    2019-12-10  2689  		 * abusers of the hotplug machinery (thermal management).
dc8d37ed304eee Arnd Bergmann    2019-12-10  2690  		 *
dc8d37ed304eee Arnd Bergmann    2019-12-10  2691  		 * So nothing would update device:offline state. That would
dc8d37ed304eee Arnd Bergmann    2019-12-10  2692  		 * leave the sysfs entry stale and prevent onlining after
dc8d37ed304eee Arnd Bergmann    2019-12-10  2693  		 * smt control has been changed to 'off' again. This is
dc8d37ed304eee Arnd Bergmann    2019-12-10  2694  		 * called under the sysfs hotplug lock, so it is properly
dc8d37ed304eee Arnd Bergmann    2019-12-10  2695  		 * serialized against the regular offline usage.
dc8d37ed304eee Arnd Bergmann    2019-12-10  2696  		 */
dc8d37ed304eee Arnd Bergmann    2019-12-10  2697  		cpuhp_offline_cpu_device(cpu);
dc8d37ed304eee Arnd Bergmann    2019-12-10  2698  	}
dc8d37ed304eee Arnd Bergmann    2019-12-10  2699  	if (!ret)
dc8d37ed304eee Arnd Bergmann    2019-12-10  2700  		cpu_smt_control = ctrlval;
dc8d37ed304eee Arnd Bergmann    2019-12-10  2701  	cpu_maps_update_done();
dc8d37ed304eee Arnd Bergmann    2019-12-10  2702  	return ret;
dc8d37ed304eee Arnd Bergmann    2019-12-10  2703  }
dc8d37ed304eee Arnd Bergmann    2019-12-10  2704  

:::::: The code at line 2681 was first introduced by commit
:::::: dc8d37ed304eeeea47e65fb9edc1c6c8b0093386 cpu/SMT: Fix x86 link error without CONFIG_SYSFS

:::::: TO: Arnd Bergmann <arnd@arndb.de>
:::::: CC: Thomas Gleixner <tglx@linutronix.de>

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