linux-imx

// SPDX-License-Identifier: GPL-2.0-only

/*

 * cpu_rmap.c: CPU affinity reverse-map support

 * Copyright 2011 Solarflare Communications Inc.

 */

​

#include <linux/cpu_rmap.h>

#include <linux/interrupt.h>

#include <linux/export.h>

​

/*

 * These functions maintain a mapping from CPUs to some ordered set of

 * objects with CPU affinities.  This can be seen as a reverse-map of

 * CPU affinity.  However, we do not assume that the object affinities

 * cover all CPUs in the system.  For those CPUs not directly covered

 * by object affinities, we attempt to find a nearest object based on

 * CPU topology.

 */

​

/**

 * alloc_cpu_rmap - allocate CPU affinity reverse-map

 * @size: Number of objects to be mapped

 * @flags: Allocation flags e.g. %GFP_KERNEL

 */

struct cpu_rmap *alloc_cpu_rmap(unsigned int size, gfp_t flags)

{

    struct cpu_rmap *rmap;

    unsigned int cpu;

    size_t obj_offset;

​

    /* This is a silly number of objects, and we use u16 indices. */

    if (size > 0xffff)

        return NULL;

​

    /* Offset of object pointer array from base structure */

    obj_offset = ALIGN(offsetof(struct cpu_rmap, near[nr_cpu_ids]),

               sizeof(void *));

​

    rmap = kzalloc(obj_offset + size * sizeof(rmap->obj[0]), flags);

    if (!rmap)

        return NULL;

​

    kref_init(&rmap->refcount);

    rmap->obj = (void **)((char *)rmap + obj_offset);

​

    /* Initially assign CPUs to objects on a rota, since we have

     * no idea where the objects are.  Use infinite distance, so

     * any object with known distance is preferable.  Include the

     * CPUs that are not present/online, since we definitely want

     * any newly-hotplugged CPUs to have some object assigned.

     */

    for_each_possible_cpu(cpu) {

        rmap->near[cpu].index = cpu % size;

        rmap->near[cpu].dist = CPU_RMAP_DIST_INF;

    }

​

    rmap->size = size;

    return rmap;

}

EXPORT_SYMBOL(alloc_cpu_rmap);

​

/**

 * cpu_rmap_release - internal reclaiming helper called from kref_put