Re: [PATCH 6/7] sched_ext: idle: Per-node idle cpumasks

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

Hi Andrea,

kernel test robot noticed the following build errors:

[auto build test ERROR on next-20250212]
[cannot apply to tip/sched/core akpm-mm/mm-everything tip/master linus/master tip/auto-latest v6.14-rc2 v6.14-rc1 v6.13 v6.14-rc2]
[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/Andrea-Righi/mm-numa-Introduce-nearest_node_nodemask/20250213-014857
base:   next-20250212
patch link:    https://lore.kernel.org/r/20250212165006.490130-7-arighi%40nvidia.com
patch subject: [PATCH 6/7] sched_ext: idle: Per-node idle cpumasks
config: i386-buildonly-randconfig-005-20250213 (https://download.01.org/0day-ci/archive/20250213/202502131834.ni8ojoRO-lkp@intel.com/config)
compiler: clang version 19.1.3 (https://github.com/llvm/llvm-project ab51eccf88f5321e7c60591c5546b254b6afab99)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250213/202502131834.ni8ojoRO-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/202502131834.ni8ojoRO-lkp@intel.com/

All errors (new ones prefixed by >>):

   In file included from kernel/sched/build_policy.c:63:
   kernel/sched/ext.c:6014:31: warning: bitwise operation between different enumeration types ('enum scx_enq_flags' and 'enum scx_deq_flags') [-Wenum-enum-conversion]
    6014 |         WRITE_ONCE(v, SCX_ENQ_WAKEUP | SCX_DEQ_SLEEP | SCX_KICK_PREEMPT |
         |                       ~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~
   include/asm-generic/rwonce.h:61:18: note: expanded from macro 'WRITE_ONCE'
      61 |         __WRITE_ONCE(x, val);                                           \
         |                         ^~~
   include/asm-generic/rwonce.h:55:33: note: expanded from macro '__WRITE_ONCE'
      55 |         *(volatile typeof(x) *)&(x) = (val);                            \
         |                                        ^~~
   In file included from kernel/sched/build_policy.c:64:
>> kernel/sched/ext_idle.c:136:9: error: '__section__' attribute only applies to functions, global variables, Objective-C methods, and Objective-C properties
     136 |         static DEFINE_PER_CPU(nodemask_t, per_cpu_unvisited);
         |                ^
   include/linux/percpu-defs.h:115:2: note: expanded from macro 'DEFINE_PER_CPU'
     115 |         DEFINE_PER_CPU_SECTION(type, name, "")
         |         ^
   include/linux/percpu-defs.h:93:2: note: expanded from macro 'DEFINE_PER_CPU_SECTION'
      93 |         __PCPU_DUMMY_ATTRS char __pcpu_unique_##name;                   \
         |         ^
   include/linux/percpu-defs.h:54:2: note: expanded from macro '__PCPU_DUMMY_ATTRS'
      54 |         __section(".discard") __attribute__((unused))
         |         ^
   include/linux/compiler_attributes.h:321:56: note: expanded from macro '__section'
     321 | #define __section(section)              __attribute__((__section__(section)))
         |                                                        ^
   In file included from kernel/sched/build_policy.c:64:
>> kernel/sched/ext_idle.c:136:9: error: non-extern declaration of '__pcpu_unique_per_cpu_unvisited' follows extern declaration
   include/linux/percpu-defs.h:115:2: note: expanded from macro 'DEFINE_PER_CPU'
     115 |         DEFINE_PER_CPU_SECTION(type, name, "")
         |         ^
   include/linux/percpu-defs.h:93:26: note: expanded from macro 'DEFINE_PER_CPU_SECTION'
      93 |         __PCPU_DUMMY_ATTRS char __pcpu_unique_##name;                   \
         |                                 ^
   <scratch space>:82:1: note: expanded from here
      82 | __pcpu_unique_per_cpu_unvisited
         | ^
   kernel/sched/ext_idle.c:136:9: note: previous declaration is here
   include/linux/percpu-defs.h:115:2: note: expanded from macro 'DEFINE_PER_CPU'
     115 |         DEFINE_PER_CPU_SECTION(type, name, "")
         |         ^
   include/linux/percpu-defs.h:92:33: note: expanded from macro 'DEFINE_PER_CPU_SECTION'
      92 |         extern __PCPU_DUMMY_ATTRS char __pcpu_unique_##name;            \
         |                                        ^
   <scratch space>:81:1: note: expanded from here
      81 | __pcpu_unique_per_cpu_unvisited
         | ^
   In file included from kernel/sched/build_policy.c:64:
>> kernel/sched/ext_idle.c:136:9: error: 'section' attribute only applies to functions, global variables, Objective-C methods, and Objective-C properties
     136 |         static DEFINE_PER_CPU(nodemask_t, per_cpu_unvisited);
         |                ^
   include/linux/percpu-defs.h:115:2: note: expanded from macro 'DEFINE_PER_CPU'
     115 |         DEFINE_PER_CPU_SECTION(type, name, "")
         |         ^
   include/linux/percpu-defs.h:95:2: note: expanded from macro 'DEFINE_PER_CPU_SECTION'
      95 |         __PCPU_ATTRS(sec) __weak __typeof__(type) name
         |         ^
   include/linux/percpu-defs.h:50:26: note: expanded from macro '__PCPU_ATTRS'
      50 |         __percpu __attribute__((section(PER_CPU_BASE_SECTION sec)))     \
         |                                 ^
   In file included from kernel/sched/build_policy.c:64:
>> kernel/sched/ext_idle.c:136:36: error: non-extern declaration of 'per_cpu_unvisited' follows extern declaration
     136 |         static DEFINE_PER_CPU(nodemask_t, per_cpu_unvisited);
         |                                           ^
   kernel/sched/ext_idle.c:136:36: note: previous declaration is here
>> kernel/sched/ext_idle.c:136:9: error: weak declaration cannot have internal linkage
     136 |         static DEFINE_PER_CPU(nodemask_t, per_cpu_unvisited);
         |                ^
   include/linux/percpu-defs.h:115:2: note: expanded from macro 'DEFINE_PER_CPU'
     115 |         DEFINE_PER_CPU_SECTION(type, name, "")
         |         ^
   include/linux/percpu-defs.h:95:20: note: expanded from macro 'DEFINE_PER_CPU_SECTION'
      95 |         __PCPU_ATTRS(sec) __weak __typeof__(type) name
         |                           ^
   include/linux/compiler_attributes.h:403:56: note: expanded from macro '__weak'
     403 | #define __weak                          __attribute__((__weak__))
         |                                                        ^
   1 warning and 5 errors generated.


vim +/__section__ +136 kernel/sched/ext_idle.c

   133	
   134	static s32 pick_idle_cpu_from_other_nodes(const struct cpumask *cpus_allowed, int node, u64 flags)
   135	{
 > 136		static DEFINE_PER_CPU(nodemask_t, per_cpu_unvisited);
   137		nodemask_t *unvisited = this_cpu_ptr(&per_cpu_unvisited);
   138		s32 cpu = -EBUSY;
   139	
   140		preempt_disable();
   141		unvisited = this_cpu_ptr(&per_cpu_unvisited);
   142	
   143		/*
   144		 * Restrict the search to the online nodes, excluding the current
   145		 * one.
   146		 */
   147		nodes_clear(*unvisited);
   148		nodes_or(*unvisited, *unvisited, node_states[N_ONLINE]);
   149		node_clear(node, *unvisited);
   150	
   151		/*
   152		 * Traverse all nodes in order of increasing distance, starting
   153		 * from @node.
   154		 *
   155		 * This loop is O(N^2), with N being the amount of NUMA nodes,
   156		 * which might be quite expensive in large NUMA systems. However,
   157		 * this complexity comes into play only when a scheduler enables
   158		 * SCX_OPS_BUILTIN_IDLE_PER_NODE and it's requesting an idle CPU
   159		 * without specifying a target NUMA node, so it shouldn't be a
   160		 * bottleneck is most cases.
   161		 *
   162		 * As a future optimization we may want to cache the list of nodes
   163		 * in a per-node array, instead of actually traversing them every
   164		 * time.
   165		 */
   166		for_each_node_numadist(node, *unvisited) {
   167			cpu = pick_idle_cpu_in_node(cpus_allowed, node, flags);
   168			if (cpu >= 0)
   169				break;
   170		}
   171		preempt_enable();
   172	
   173		return cpu;
   174	}
   175	

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