C++ rcu_read_lock_bh函数代码示例

int display_bytes_array(void)
{
	struct bytes tmp;
	int i;

	rcu_read_lock_bh();
	tmp = *rcu_dereference(bytes_to_skip);

	if (!tmp.count) {
		log_info("Byte array list is empty");
		goto end;
	}

	for (i = 0; i < tmp.count; i++) {
		if (i + 1 != tmp.count)
			printk("%u, ", tmp.array[i]);
		else
			printk("%u\n", tmp.array[i]);
	}
	log_info("Array length: %d", tmp.count);

end:
	rcu_read_unlock_bh();
	return 0;
}

/* modelled after ip6_finish_output2 */
static int vrf_finish_output6(struct net *net, struct sock *sk,
			      struct sk_buff *skb)
{
	struct dst_entry *dst = skb_dst(skb);
	struct net_device *dev = dst->dev;
	struct neighbour *neigh;
	struct in6_addr *nexthop;
	int ret;

	skb->protocol = htons(ETH_P_IPV6);
	skb->dev = dev;

	rcu_read_lock_bh();
	nexthop = rt6_nexthop((struct rt6_info *)dst, &ipv6_hdr(skb)->daddr);
	neigh = __ipv6_neigh_lookup_noref(dst->dev, nexthop);
	if (unlikely(!neigh))
		neigh = __neigh_create(&nd_tbl, nexthop, dst->dev, false);
	if (!IS_ERR(neigh)) {
		ret = dst_neigh_output(dst, neigh, skb);
		rcu_read_unlock_bh();
		return ret;
	}
	rcu_read_unlock_bh();

	IP6_INC_STATS(dev_net(dst->dev),
		      ip6_dst_idev(dst), IPSTATS_MIB_OUTNOROUTES);
	kfree_skb(skb);
	return -EINVAL;
}

/**
 * Copies this module's current configuration to "clone".
 *
 * @param[out] clone a copy of the current config will be placed here. Must be already allocated.
 * @return zero on success, nonzero on failure.
 */
int filtering_clone_config(struct filtering_config *clone)
{
	rcu_read_lock_bh();
	*clone = *rcu_dereference_bh(config);
	rcu_read_unlock_bh();
	return 0;
}

int flush_bytes_array(void)
{
	struct bytes *tmp, *old;

	rcu_read_lock_bh();
	if (!(rcu_dereference_bh(bytes_to_skip)->array)) {
		log_info("Byte array list is empty nothing to flush");
		rcu_read_unlock_bh();
		return 0;
	}
	rcu_read_unlock_bh();

	tmp = kmalloc(sizeof(*tmp), GFP_KERNEL);
	if (!tmp) {
		log_err("Could not allocate struct bytes.");
		return -ENOMEM;
	}

	old = bytes_to_skip;
	*tmp = *bytes_to_skip;

	/* Delete. */
	tmp->array = NULL;
	tmp->count = 0;

	rcu_assign_pointer(bytes_to_skip, tmp);
	synchronize_rcu_bh();

	if (old->array)
		kfree(old->array);

	kfree(old);
	return 0;
}

static void vhost_zerocopy_callback(struct ubuf_info *ubuf, bool success)
{
	struct vhost_net_ubuf_ref *ubufs = ubuf->ctx;
	struct vhost_virtqueue *vq = ubufs->vq;
	int cnt;

	rcu_read_lock_bh();

	/* set len to mark this desc buffers done DMA */
	vq->heads[ubuf->desc].len = success ?
		VHOST_DMA_DONE_LEN : VHOST_DMA_FAILED_LEN;
	cnt = vhost_net_ubuf_put(ubufs);

	/*
	 * Trigger polling thread if guest stopped submitting new buffers:
	 * in this case, the refcount after decrement will eventually reach 1.
	 * We also trigger polling periodically after each 16 packets
	 * (the value 16 here is more or less arbitrary, it's tuned to trigger
	 * less than 10% of times).
	 */
	if (cnt <= 1 || !(cnt % 16))
		vhost_poll_queue(&vq->poll);

	rcu_read_unlock_bh();
}

/**
 * Use this function to safely obtain the configuration value which dictates whether IPv4 nodes
 * should be allowed to initiate conversations with IPv6 nodes.
 *
 * @return whether IPv4 nodes should be allowed to initiate conversations with IPv6 nodes.
 */
static bool drop_external_connections(void)
{
	bool result;

	rcu_read_lock_bh();
	result = rcu_dereference_bh(config)->drop_external_tcp;
	rcu_read_unlock_bh();

	return result;
}

/**
 * Use this function to safely obtain the configuration value which dictates whether Jool should
 * drop all informational ICMP packets that are traveling from IPv6 to IPv4.
 *
 * @return whether Jool should drop all ICMPv6 info packets.
 */
static bool filter_icmpv6_info(void)
{
	bool result;

	rcu_read_lock_bh();
	result = rcu_dereference_bh(config)->drop_icmp6_info;
	rcu_read_unlock_bh();

	return result;
}

/**
 * Use this function to safely obtain the configuration value which dictates whether Jool should
 * be applying "address-dependent filtering" (Look that up in the RFC).
 *
 * @return whether Jool should apply "address-dependent filtering".
 */
static bool address_dependent_filtering(void)
{
	bool result;

	rcu_read_lock_bh();
	result = rcu_dereference_bh(config)->drop_by_addr;
	rcu_read_unlock_bh();

	return result;
}

struct llc_sap *llc_sap_find(unsigned char sap_value)
{
	struct llc_sap *sap;

	rcu_read_lock_bh();
	sap = __llc_sap_find(sap_value);
	if (sap)
		llc_sap_hold(sap);
	rcu_read_unlock_bh();
	return sap;
}

static struct ip6_flowlabel *fl_lookup(struct net *net, __be32 label)
{
	struct ip6_flowlabel *fl;

	rcu_read_lock_bh();
	fl = __fl_lookup(net, label);
	if (fl && !atomic_inc_not_zero(&fl->users))
		fl = NULL;
	rcu_read_unlock_bh();
	return fl;
}

static struct nfulnl_instance *
instance_lookup_get(struct nfnl_log_net *log, u_int16_t group_num)
{
	struct nfulnl_instance *inst;

	rcu_read_lock_bh();
	inst = __instance_lookup(log, group_num);
	if (inst && !refcount_inc_not_zero(&inst->use))
		inst = NULL;
	rcu_read_unlock_bh();

	return inst;
}

/* modelled after ip_finish_output2 */
static int vrf_finish_output(struct net *net, struct sock *sk, struct sk_buff *skb)
{
	struct dst_entry *dst = skb_dst(skb);
	struct rtable *rt = (struct rtable *)dst;
	struct net_device *dev = dst->dev;
	unsigned int hh_len = LL_RESERVED_SPACE(dev);
	struct neighbour *neigh;
	u32 nexthop;
	int ret = -EINVAL;

	nf_reset(skb);

	/* Be paranoid, rather than too clever. */
	if (unlikely(skb_headroom(skb) < hh_len && dev->header_ops)) {
		struct sk_buff *skb2;

		skb2 = skb_realloc_headroom(skb, LL_RESERVED_SPACE(dev));
		if (!skb2) {
			ret = -ENOMEM;
			goto err;
		}
		if (skb->sk)
			skb_set_owner_w(skb2, skb->sk);

		consume_skb(skb);
		skb = skb2;
	}

	rcu_read_lock_bh();

	nexthop = (__force u32)rt_nexthop(rt, ip_hdr(skb)->daddr);
	neigh = __ipv4_neigh_lookup_noref(dev, nexthop);
	if (unlikely(!neigh))
		neigh = __neigh_create(&arp_tbl, &nexthop, dev, false);
	if (!IS_ERR(neigh)) {
		sock_confirm_neigh(skb, neigh);
		ret = neigh_output(neigh, skb);
		rcu_read_unlock_bh();
		return ret;
	}

	rcu_read_unlock_bh();
err:
	vrf_tx_error(skb->dev, skb);
	return ret;
}

struct ip6_flowlabel *fl6_sock_lookup(struct sock *sk, __be32 label)
{
	struct ipv6_fl_socklist *sfl;
	struct ipv6_pinfo *np = inet6_sk(sk);

	label &= IPV6_FLOWLABEL_MASK;

	rcu_read_lock_bh();
	for_each_sk_fl_rcu(np, sfl) {
		struct ip6_flowlabel *fl = sfl->fl;
		if (fl->label == label) {
			fl->lastuse = jiffies;
			atomic_inc(&fl->users);
			rcu_read_unlock_bh();
			return fl;
		}
	}
	rcu_read_unlock_bh();
	return NULL;
}

bool skb_compare(struct sk_buff *expected, struct sk_buff *actual)
{
	struct bytes *skip_byte;
	unsigned char *expected_ptr, *actual_ptr;
	unsigned int i, min_len, skip_count;
	int errors = 0;

	if (expected->len != actual->len) {
		print_error_table_hdr(errors);
		log_info("    Length\t%d\t    %d", expected->len, actual->len);
		errors++;
	}

	expected_ptr = skb_network_header(expected);
	actual_ptr = skb_network_header(actual);
	min_len = (expected->len < actual->len) ? expected->len : actual->len;

	rcu_read_lock_bh();
	skip_byte = rcu_dereference_bh(bytes_to_skip);
	skip_count = 0;

	for (i = 0; i < min_len; i++) {
		if (skip_count < skip_byte->count && skip_byte->array[skip_count] == i) {
			skip_count++;
			continue;
		}

		if (expected_ptr[i] != actual_ptr[i]) {
			print_error_table_hdr(errors);
			log_info("    byte %u\t0x%x\t    0x%x", i,
					expected_ptr[i], actual_ptr[i]);
			errors++;
			if (errors >= 8)
				break;
		}
	}

	rcu_read_unlock_bh();
	return !errors;
}

static struct neighbour *hwaddr_neighbour(struct rtable *rt,
			struct hwaddr_entry *entry)
{
#if LINUX_VERSION_CODE < KERNEL_VERSION(3,1,0)
	struct neighbour *neigh = rt->dst.neighbour;
#else
	struct neighbour *neigh = NULL;
	__be32 next = 0;

	rcu_read_lock_bh();
	next = rt_nexthop(rt, entry->h_remote);
	neigh = __ipv4_neigh_lookup_noref(rt->dst.dev, next);
	if (IS_ERR_OR_NULL(neigh))
		neigh = __neigh_create(&arp_tbl, &next, rt->dst.dev, false);
	rcu_read_unlock_bh();
#endif

	if (IS_ERR(neigh))
		return NULL;

	return neigh;
}