root/drivers/net/wireguard/queueing.c
// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
 */

#include "queueing.h"
#include <linux/skb_array.h>

struct multicore_worker __percpu *
wg_packet_percpu_multicore_worker_alloc(work_func_t function, void *ptr)
{
        int cpu;
        struct multicore_worker __percpu *worker = alloc_percpu(struct multicore_worker);

        if (!worker)
                return NULL;

        for_each_possible_cpu(cpu) {
                per_cpu_ptr(worker, cpu)->ptr = ptr;
                INIT_WORK(&per_cpu_ptr(worker, cpu)->work, function);
        }
        return worker;
}

int wg_packet_queue_init(struct crypt_queue *queue, work_func_t function,
                         unsigned int len)
{
        int ret;

        memset(queue, 0, sizeof(*queue));
        queue->last_cpu = -1;
        ret = ptr_ring_init(&queue->ring, len, GFP_KERNEL);
        if (ret)
                return ret;
        queue->worker = wg_packet_percpu_multicore_worker_alloc(function, queue);
        if (!queue->worker) {
                ptr_ring_cleanup(&queue->ring, NULL);
                return -ENOMEM;
        }
        return 0;
}

void wg_packet_queue_free(struct crypt_queue *queue, bool purge)
{
        free_percpu(queue->worker);
        WARN_ON(!purge && !__ptr_ring_empty(&queue->ring));
        ptr_ring_cleanup(&queue->ring, purge ? __skb_array_destroy_skb : NULL);
}

#define NEXT(skb) ((skb)->prev)
#define STUB(queue) ((struct sk_buff *)&queue->empty)

void wg_prev_queue_init(struct prev_queue *queue)
{
        NEXT(STUB(queue)) = NULL;
        queue->head = queue->tail = STUB(queue);
        queue->peeked = NULL;
        atomic_set(&queue->count, 0);
        BUILD_BUG_ON(
                offsetof(struct sk_buff, next) != offsetof(struct prev_queue, empty.next) -
                                                        offsetof(struct prev_queue, empty) ||
                offsetof(struct sk_buff, prev) != offsetof(struct prev_queue, empty.prev) -
                                                         offsetof(struct prev_queue, empty));
}

static void __wg_prev_queue_enqueue(struct prev_queue *queue, struct sk_buff *skb)
{
        WRITE_ONCE(NEXT(skb), NULL);
        WRITE_ONCE(NEXT(xchg_release(&queue->head, skb)), skb);
}

bool wg_prev_queue_enqueue(struct prev_queue *queue, struct sk_buff *skb)
{
        if (!atomic_add_unless(&queue->count, 1, MAX_QUEUED_PACKETS))
                return false;
        __wg_prev_queue_enqueue(queue, skb);
        return true;
}

struct sk_buff *wg_prev_queue_dequeue(struct prev_queue *queue)
{
        struct sk_buff *tail = queue->tail, *next = smp_load_acquire(&NEXT(tail));

        if (tail == STUB(queue)) {
                if (!next)
                        return NULL;
                queue->tail = next;
                tail = next;
                next = smp_load_acquire(&NEXT(next));
        }
        if (next) {
                queue->tail = next;
                atomic_dec(&queue->count);
                return tail;
        }
        if (tail != READ_ONCE(queue->head))
                return NULL;
        __wg_prev_queue_enqueue(queue, STUB(queue));
        next = smp_load_acquire(&NEXT(tail));
        if (next) {
                queue->tail = next;
                atomic_dec(&queue->count);
                return tail;
        }
        return NULL;
}

#undef NEXT
#undef STUB