void __init setup_per_cpu_areas()

in mm/discontig.c [180:250]

• 55 lines of code
• 6 McCabe index (conditional complexity)

void __init setup_per_cpu_areas(void)
{
	struct pcpu_alloc_info *ai;
	struct pcpu_group_info *gi;
	unsigned int *cpu_map;
	void *base;
	unsigned long base_offset;
	unsigned int cpu;
	ssize_t static_size, reserved_size, dyn_size;
	int node, prev_node, unit, nr_units;

	ai = pcpu_alloc_alloc_info(MAX_NUMNODES, nr_cpu_ids);
	if (!ai)
		panic("failed to allocate pcpu_alloc_info");
	cpu_map = ai->groups[0].cpu_map;

	/* determine base */
	base = (void *)ULONG_MAX;
	for_each_possible_cpu(cpu)
		base = min(base,
			   (void *)(__per_cpu_offset[cpu] + __per_cpu_start));
	base_offset = (void *)__per_cpu_start - base;

	/* build cpu_map, units are grouped by node */
	unit = 0;
	for_each_node(node)
		for_each_possible_cpu(cpu)
			if (node == node_cpuid[cpu].nid)
				cpu_map[unit++] = cpu;
	nr_units = unit;

	/* set basic parameters */
	static_size = __per_cpu_end - __per_cpu_start;
	reserved_size = PERCPU_MODULE_RESERVE;
	dyn_size = PERCPU_PAGE_SIZE - static_size - reserved_size;
	if (dyn_size < 0)
		panic("percpu area overflow static=%zd reserved=%zd\n",
		      static_size, reserved_size);

	ai->static_size		= static_size;
	ai->reserved_size	= reserved_size;
	ai->dyn_size		= dyn_size;
	ai->unit_size		= PERCPU_PAGE_SIZE;
	ai->atom_size		= PAGE_SIZE;
	ai->alloc_size		= PERCPU_PAGE_SIZE;

	/*
	 * CPUs are put into groups according to node.  Walk cpu_map
	 * and create new groups at node boundaries.
	 */
	prev_node = NUMA_NO_NODE;
	ai->nr_groups = 0;
	for (unit = 0; unit < nr_units; unit++) {
		cpu = cpu_map[unit];
		node = node_cpuid[cpu].nid;

		if (node == prev_node) {
			gi->nr_units++;
			continue;
		}
		prev_node = node;

		gi = &ai->groups[ai->nr_groups++];
		gi->nr_units		= 1;
		gi->base_offset		= __per_cpu_offset[cpu] + base_offset;
		gi->cpu_map		= &cpu_map[unit];
	}

	pcpu_setup_first_chunk(ai, base);
	pcpu_free_alloc_info(ai);
}