C++ RCU_INIT_POINTER函数代码示例

static int __init nf_nat_init(void)
{
	int ret;

	ret = rhltable_init(&nf_nat_bysource_table, &nf_nat_bysource_params);
	if (ret)
		return ret;

	ret = nf_ct_extend_register(&nat_extend);
	if (ret < 0) {
		rhltable_destroy(&nf_nat_bysource_table);
		printk(KERN_ERR "nf_nat_core: Unable to register extension\n");
		return ret;
	}

	ret = register_pernet_subsys(&nf_nat_net_ops);
	if (ret < 0)
		goto cleanup_extend;

	nf_ct_helper_expectfn_register(&follow_master_nat);

	BUG_ON(nfnetlink_parse_nat_setup_hook != NULL);
	RCU_INIT_POINTER(nfnetlink_parse_nat_setup_hook,
			   nfnetlink_parse_nat_setup);
#ifdef CONFIG_XFRM
	BUG_ON(nf_nat_decode_session_hook != NULL);
	RCU_INIT_POINTER(nf_nat_decode_session_hook, __nf_nat_decode_session);
#endif
	return 0;

 cleanup_extend:
	rhltable_destroy(&nf_nat_bysource_table);
	nf_ct_extend_unregister(&nat_extend);
	return ret;
}

/* holding rtnl */
static void vrf_rtable_release(struct net_device *dev, struct net_vrf *vrf)
{
	struct rtable *rth = rtnl_dereference(vrf->rth);
	struct rtable *rth_local = rtnl_dereference(vrf->rth_local);
	struct net *net = dev_net(dev);
	struct dst_entry *dst;

	RCU_INIT_POINTER(vrf->rth, NULL);
	RCU_INIT_POINTER(vrf->rth_local, NULL);
	synchronize_rcu();

	/* move dev in dst's to loopback so this VRF device can be deleted
	 * - based on dst_ifdown
	 */
	if (rth) {
		dst = &rth->dst;
		dev_put(dst->dev);
		dst->dev = net->loopback_dev;
		dev_hold(dst->dev);
		dst_release(dst);
	}

	if (rth_local) {
		dst = &rth_local->dst;
		dev_put(dst->dev);
		dst->dev = net->loopback_dev;
		dev_hold(dst->dev);
		dst_release(dst);
	}
}

static int __init nx842_pseries_init(void)
{
	struct nx842_devdata *new_devdata;
	int ret;

	if (!of_find_compatible_node(NULL, NULL, "ibm,compression"))
		return -ENODEV;

	RCU_INIT_POINTER(devdata, NULL);
	new_devdata = kzalloc(sizeof(*new_devdata), GFP_KERNEL);
	if (!new_devdata) {
		pr_err("Could not allocate memory for device data\n");
		return -ENOMEM;
	}
	RCU_INIT_POINTER(devdata, new_devdata);

	ret = vio_register_driver(&nx842_vio_driver);
	if (ret) {
		pr_err("Could not register VIO driver %d\n", ret);

		kfree(new_devdata);
		return ret;
	}

	return 0;
}

void wg_noise_keypairs_clear(struct noise_keypairs *keypairs)
{
	struct noise_keypair *old;

	spin_lock_bh(&keypairs->keypair_update_lock);

	/* We zero the next_keypair before zeroing the others, so that
	 * wg_noise_received_with_keypair returns early before subsequent ones
	 * are zeroed.
	 */
	old = rcu_dereference_protected(keypairs->next_keypair,
		lockdep_is_held(&keypairs->keypair_update_lock));
	RCU_INIT_POINTER(keypairs->next_keypair, NULL);
	wg_noise_keypair_put(old, true);

	old = rcu_dereference_protected(keypairs->previous_keypair,
		lockdep_is_held(&keypairs->keypair_update_lock));
	RCU_INIT_POINTER(keypairs->previous_keypair, NULL);
	wg_noise_keypair_put(old, true);

	old = rcu_dereference_protected(keypairs->current_keypair,
		lockdep_is_held(&keypairs->keypair_update_lock));
	RCU_INIT_POINTER(keypairs->current_keypair, NULL);
	wg_noise_keypair_put(old, true);

	spin_unlock_bh(&keypairs->keypair_update_lock);
}

struct sw_flow *ovs_flow_alloc(void)
{
	struct sw_flow *flow;
	struct flow_stats *stats;
	int node;

	flow = kmem_cache_alloc(flow_cache, GFP_KERNEL);
	if (!flow)
		return ERR_PTR(-ENOMEM);

	flow->sf_acts = NULL;
	flow->mask = NULL;
	flow->stats_last_writer = NUMA_NO_NODE;

	/* Initialize the default stat node. */
	stats = kmem_cache_alloc_node(flow_stats_cache,
				      GFP_KERNEL | __GFP_ZERO, 0);
	if (!stats)
		goto err;

	spin_lock_init(&stats->lock);

	RCU_INIT_POINTER(flow->stats[0], stats);

	for_each_node(node)
		if (node != 0)
			RCU_INIT_POINTER(flow->stats[node], NULL);

	return flow;
err:
	kmem_cache_free(flow_cache, flow);
	return ERR_PTR(-ENOMEM);
}

static int __init init(void)
{
	printk("nf_nat_rtsp v" IP_NF_RTSP_VERSION " loading\n");

	if (stunaddr != NULL)
		extip = in_aton(stunaddr);

	if (destaction != NULL) {
	        if (strcmp(destaction, "auto") == 0)
			dstact = DSTACT_AUTO;

		if (strcmp(destaction, "strip") == 0)
			dstact = DSTACT_STRIP;

		if (strcmp(destaction, "none") == 0)
			dstact = DSTACT_NONE;
	}

	BUG_ON(rcu_dereference(nf_nat_rtsp_hook));
	RCU_INIT_POINTER(nf_nat_rtsp_hook, help);

	BUG_ON(rcu_dereference(nf_nat_rtsp_hook_expectfn));
	RCU_INIT_POINTER(nf_nat_rtsp_hook_expectfn, expected);

	return 0;
}

static void
reservation_object_add_shared_replace(struct reservation_object *obj,
				      struct reservation_object_list *old,
				      struct reservation_object_list *fobj,
				      struct fence *fence)
{
	unsigned i;
	struct fence *old_fence = NULL;

	fence_get(fence);

	if (!old) {
		RCU_INIT_POINTER(fobj->shared[0], fence);
		fobj->shared_count = 1;
		goto done;
	}

	/*
	 * no need to bump fence refcounts, rcu_read access
	 * requires the use of kref_get_unless_zero, and the
	 * references from the old struct are carried over to
	 * the new.
	 */
	fobj->shared_count = old->shared_count;

	for (i = 0; i < old->shared_count; ++i) {
		struct fence *check;

		check = rcu_dereference_protected(old->shared[i],
						reservation_object_held(obj));

		if (!old_fence && check->context == fence->context) {
			old_fence = check;
			RCU_INIT_POINTER(fobj->shared[i], fence);
		} else
			RCU_INIT_POINTER(fobj->shared[i], check);
	}
	if (!old_fence) {
		RCU_INIT_POINTER(fobj->shared[fobj->shared_count], fence);
		fobj->shared_count++;
	}

done:
	preempt_disable();
	write_seqcount_begin(&obj->seq);
	/*
	 * RCU_INIT_POINTER can be used here,
	 * seqcount provides the necessary barriers
	 */
	RCU_INIT_POINTER(obj->fence, fobj);
	write_seqcount_end(&obj->seq);
	preempt_enable();

	if (old)
		kfree_rcu(old, rcu);

	if (old_fence)
		fence_put(old_fence);
}

static void __exit nf_nat_helper_pptp_fini(void)
{
	RCU_INIT_POINTER(nf_nat_pptp_hook_expectfn, NULL);
	RCU_INIT_POINTER(nf_nat_pptp_hook_exp_gre, NULL);
	RCU_INIT_POINTER(nf_nat_pptp_hook_inbound, NULL);
	RCU_INIT_POINTER(nf_nat_pptp_hook_outbound, NULL);
	synchronize_rcu();
}

/* tipc_disable_l2_media - detach TIPC bearer from an L2 interface
 *
 * Mark L2 bearer as inactive so that incoming buffers are thrown away,
 * then get worker thread to complete bearer cleanup.  (Can't do cleanup
 * here because cleanup code needs to sleep and caller holds spinlocks.)
 */
void tipc_disable_l2_media(struct tipc_bearer *b)
{
	struct net_device *dev;

	dev = (struct net_device *)rtnl_dereference(b->media_ptr);
	RCU_INIT_POINTER(b->media_ptr, NULL);
	RCU_INIT_POINTER(dev->tipc_ptr, NULL);
	synchronize_net();
	dev_put(dev);
}

int ip_ra_control(struct sock *sk, unsigned char on,
		  void (*destructor)(struct sock *))
{
	struct ip_ra_chain *ra, *new_ra;
	struct ip_ra_chain __rcu **rap;
	struct net *net = sock_net(sk);

	if (sk->sk_type != SOCK_RAW || inet_sk(sk)->inet_num == IPPROTO_RAW)
		return -EINVAL;

	new_ra = on ? kmalloc(sizeof(*new_ra), GFP_KERNEL) : NULL;

	mutex_lock(&net->ipv4.ra_mutex);
	for (rap = &net->ipv4.ra_chain;
	     (ra = rcu_dereference_protected(*rap,
			lockdep_is_held(&net->ipv4.ra_mutex))) != NULL;
	     rap = &ra->next) {
		if (ra->sk == sk) {
			if (on) {
				mutex_unlock(&net->ipv4.ra_mutex);
				kfree(new_ra);
				return -EADDRINUSE;
			}
			/* dont let ip_call_ra_chain() use sk again */
			ra->sk = NULL;
			RCU_INIT_POINTER(*rap, ra->next);
			mutex_unlock(&net->ipv4.ra_mutex);

			if (ra->destructor)
				ra->destructor(sk);
			/*
			 * Delay sock_put(sk) and kfree(ra) after one rcu grace
			 * period. This guarantee ip_call_ra_chain() dont need
			 * to mess with socket refcounts.
			 */
			ra->saved_sk = sk;
			call_rcu(&ra->rcu, ip_ra_destroy_rcu);
			return 0;
		}
	}
	if (!new_ra) {
		mutex_unlock(&net->ipv4.ra_mutex);
		return -ENOBUFS;
	}
	new_ra->sk = sk;
	new_ra->destructor = destructor;

	RCU_INIT_POINTER(new_ra->next, ra);
	rcu_assign_pointer(*rap, new_ra);
	sock_hold(sk);
	mutex_unlock(&net->ipv4.ra_mutex);

	return 0;
}

static void __vlan_flush(struct net_port_vlans *v)
{
	smp_wmb();
	v->pvid = 0;
	bitmap_zero(v->vlan_bitmap, VLAN_N_VID);
	if (v->port_idx)
		RCU_INIT_POINTER(v->parent.port->vlan_info, NULL);
	else
		RCU_INIT_POINTER(v->parent.br->vlan_info, NULL);
	kfree_rcu(v, rcu);
}

static void add_new_keypair(struct noise_keypairs *keypairs,
			    struct noise_keypair *new_keypair)
{
	struct noise_keypair *previous_keypair, *next_keypair, *current_keypair;

	spin_lock_bh(&keypairs->keypair_update_lock);
	previous_keypair = rcu_dereference_protected(keypairs->previous_keypair,
		lockdep_is_held(&keypairs->keypair_update_lock));
	next_keypair = rcu_dereference_protected(keypairs->next_keypair,
		lockdep_is_held(&keypairs->keypair_update_lock));
	current_keypair = rcu_dereference_protected(keypairs->current_keypair,
		lockdep_is_held(&keypairs->keypair_update_lock));
	if (new_keypair->i_am_the_initiator) {
		/* If we're the initiator, it means we've sent a handshake, and
		 * received a confirmation response, which means this new
		 * keypair can now be used.
		 */
		if (next_keypair) {
			/* If there already was a next keypair pending, we
			 * demote it to be the previous keypair, and free the
			 * existing current. Note that this means KCI can result
			 * in this transition. It would perhaps be more sound to
			 * always just get rid of the unused next keypair
			 * instead of putting it in the previous slot, but this
			 * might be a bit less robust. Something to think about
			 * for the future.
			 */
			RCU_INIT_POINTER(keypairs->next_keypair, NULL);
			rcu_assign_pointer(keypairs->previous_keypair,
					   next_keypair);
			wg_noise_keypair_put(current_keypair, true);
		} else /* If there wasn't an existing next keypair, we replace
			* the previous with the current one.
			*/
			rcu_assign_pointer(keypairs->previous_keypair,
					   current_keypair);
		/* At this point we can get rid of the old previous keypair, and
		 * set up the new keypair.
		 */
		wg_noise_keypair_put(previous_keypair, true);
		rcu_assign_pointer(keypairs->current_keypair, new_keypair);
	} else {
		/* If we're the responder, it means we can't use the new keypair
		 * until we receive confirmation via the first data packet, so
		 * we get rid of the existing previous one, the possibly
		 * existing next one, and slide in the new next one.
		 */
		rcu_assign_pointer(keypairs->next_keypair, new_keypair);
		wg_noise_keypair_put(next_keypair, true);
		RCU_INIT_POINTER(keypairs->previous_keypair, NULL);
		wg_noise_keypair_put(previous_keypair, true);
	}
	spin_unlock_bh(&keypairs->keypair_update_lock);
}

/**
 * bearer_disable
 *
 * Note: This routine assumes caller holds RTNL lock.
 */
static void bearer_disable(struct net *net, struct tipc_bearer *b)
{
	struct tipc_net *tn = tipc_net(net);
	int bearer_id = b->identity;

	pr_info("Disabling bearer <%s>\n", b->name);
	b->media->disable_media(b);
	tipc_node_delete_links(net, bearer_id);
	RCU_INIT_POINTER(b->media_ptr, NULL);
	if (b->link_req)
		tipc_disc_delete(b->link_req);
	RCU_INIT_POINTER(tn->bearer_list[bearer_id], NULL);
	kfree_rcu(b, rcu);
}

void stp_proto_unregister(const struct stp_proto *proto)
{
	mutex_lock(&stp_proto_mutex);
	if (is_zero_ether_addr(proto->group_address))
		RCU_INIT_POINTER(stp_proto, NULL);
	else
		RCU_INIT_POINTER(garp_protos[proto->group_address[5] -
					       GARP_ADDR_MIN], NULL);
	synchronize_rcu();

	if (--sap_registered == 0)
		llc_sap_put(sap);
	mutex_unlock(&stp_proto_mutex);
}

static int __init nf_nat_helper_pptp_init(void)
{
	BUG_ON(nf_nat_pptp_hook_outbound != NULL);
	RCU_INIT_POINTER(nf_nat_pptp_hook_outbound, pptp_outbound_pkt);

	BUG_ON(nf_nat_pptp_hook_inbound != NULL);
	RCU_INIT_POINTER(nf_nat_pptp_hook_inbound, pptp_inbound_pkt);

	BUG_ON(nf_nat_pptp_hook_exp_gre != NULL);
	RCU_INIT_POINTER(nf_nat_pptp_hook_exp_gre, pptp_exp_gre);

	BUG_ON(nf_nat_pptp_hook_expectfn != NULL);
	RCU_INIT_POINTER(nf_nat_pptp_hook_expectfn, pptp_nat_expected);
	return 0;
}