Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 67db3e4b authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

tcp: no longer hold ehash lock while calling tcp_get_info() 



We had various problems in the past in tcp_get_info() and used
specific synchronization to avoid deadlocks.

We would like to add more instrumentation points for TCP, and
avoiding grabing socket lock in tcp_getinfo() was too costly.

Being able to lock the socket allows to provide consistent set
of fields.

inet_diag_dump_icsk() can make sure ehash locks are not
held any more when tcp_get_info() is called.

We can remove syncp added in commit d654976c
("tcp: fix a potential deadlock in tcp_get_info()"), but we need
to use lock_sock_fast() instead of spin_lock_bh() since TCP input
path can now be run from process context.

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarYuchung Cheng <ycheng@google.com>
Acked-by: default avatarSoheil Hassas Yeganeh <soheil@google.com>
Acked-by: default avatarNeal Cardwell <ncardwell@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent ccbf3bfa

include/linux/tcp.h

+0 −2
Original line number Diff line number Diff line
@@ -176,8 +176,6 @@ struct tcp_sock { 
				 * sum(delta(snd_una)), or how many bytes

				 * were acked.

				 */

	struct u64_stats_sync syncp; /* protects 64bit vars (cf tcp_get_info()) */



 	u32	snd_una;	/* First byte we want an ack for	*/

 	u32	snd_sml;	/* Last byte of the most recently transmitted small packet */

	u32	rcv_tstamp;	/* timestamp of last received ACK (for keepalives) */

net/ipv4/inet_diag.c

+33 −15
Original line number Diff line number Diff line
@@ -861,10 +861,11 @@ void inet_diag_dump_icsk(struct inet_hashinfo *hashinfo, struct sk_buff *skb, 
			 struct netlink_callback *cb,

			 const struct inet_diag_req_v2 *r, struct nlattr *bc)

{

	bool net_admin = netlink_net_capable(cb->skb, CAP_NET_ADMIN);

	struct net *net = sock_net(skb->sk);

	int i, num, s_i, s_num;

	u32 idiag_states = r->idiag_states;

	bool net_admin = netlink_net_capable(cb->skb, CAP_NET_ADMIN);

	int i, num, s_i, s_num;

	struct sock *sk;



	if (idiag_states & TCPF_SYN_RECV)

		idiag_states |= TCPF_NEW_SYN_RECV;
@@ -877,7 +878,6 @@ void inet_diag_dump_icsk(struct inet_hashinfo *hashinfo, struct sk_buff *skb, 


		for (i = s_i; i < INET_LHTABLE_SIZE; i++) {

			struct inet_listen_hashbucket *ilb;

			struct sock *sk;



			num = 0;

			ilb = &hashinfo->listening_hash[i];
@@ -922,13 +922,14 @@ void inet_diag_dump_icsk(struct inet_hashinfo *hashinfo, struct sk_buff *skb, 
	if (!(idiag_states & ~TCPF_LISTEN))

		goto out;



#define SKARR_SZ 16

	for (i = s_i; i <= hashinfo->ehash_mask; i++) {

		struct inet_ehash_bucket *head = &hashinfo->ehash[i];

		spinlock_t *lock = inet_ehash_lockp(hashinfo, i);

		struct hlist_nulls_node *node;

		struct sock *sk;



		num = 0;

		struct sock *sk_arr[SKARR_SZ];

		int num_arr[SKARR_SZ];

		int idx, accum, res;



		if (hlist_nulls_empty(&head->chain))

			continue;
@@ -936,9 +937,12 @@ void inet_diag_dump_icsk(struct inet_hashinfo *hashinfo, struct sk_buff *skb, 
		if (i > s_i)

			s_num = 0;



next_chunk:

		num = 0;

		accum = 0;

		spin_lock_bh(lock);

		sk_nulls_for_each(sk, node, &head->chain) {

			int state, res;

			int state;



			if (!net_eq(sock_net(sk), net))

				continue;
@@ -962,21 +966,35 @@ void inet_diag_dump_icsk(struct inet_hashinfo *hashinfo, struct sk_buff *skb, 
			if (!inet_diag_bc_sk(bc, sk))

				goto next_normal;



			res = sk_diag_fill(sk, skb, r,

			sock_hold(sk);

			num_arr[accum] = num;

			sk_arr[accum] = sk;

			if (++accum == SKARR_SZ)

				break;

next_normal:

			++num;

		}

		spin_unlock_bh(lock);

		res = 0;

		for (idx = 0; idx < accum; idx++) {

			if (res >= 0) {

				res = sk_diag_fill(sk_arr[idx], skb, r,

					   sk_user_ns(NETLINK_CB(cb->skb).sk),

					   NETLINK_CB(cb->skb).portid,

					   cb->nlh->nlmsg_seq, NLM_F_MULTI,

					   cb->nlh, net_admin);

			if (res < 0) {

				spin_unlock_bh(lock);

				goto done;

				if (res < 0)

					num = num_arr[idx];

			}

next_normal:

			++num;

			sock_gen_put(sk_arr[idx]);

		}



		spin_unlock_bh(lock);

		if (res < 0)

			break;

		cond_resched();

		if (accum == SKARR_SZ) {

			s_num = num + 1;

			goto next_chunk;

		}

	}



done:

net/ipv4/tcp.c

+9 −11
Original line number Diff line number Diff line
@@ -405,7 +405,6 @@ void tcp_init_sock(struct sock *sk) 
	tp->snd_ssthresh = TCP_INFINITE_SSTHRESH;

	tp->snd_cwnd_clamp = ~0;

	tp->mss_cache = TCP_MSS_DEFAULT;

	u64_stats_init(&tp->syncp);



	tp->reordering = sock_net(sk)->ipv4.sysctl_tcp_reordering;

	tcp_enable_early_retrans(tp);
@@ -2710,9 +2709,8 @@ void tcp_get_info(struct sock *sk, struct tcp_info *info) 
	const struct tcp_sock *tp = tcp_sk(sk); /* iff sk_type == SOCK_STREAM */

	const struct inet_connection_sock *icsk = inet_csk(sk);

	u32 now = tcp_time_stamp, intv;

	unsigned int start;

	int notsent_bytes;

	u64 rate64;

	bool slow;

	u32 rate;



	memset(info, 0, sizeof(*info));
@@ -2792,17 +2790,17 @@ void tcp_get_info(struct sock *sk, struct tcp_info *info) 


	info->tcpi_total_retrans = tp->total_retrans;



	do {

		start = u64_stats_fetch_begin_irq(&tp->syncp);

	slow = lock_sock_fast(sk);



	put_unaligned(tp->bytes_acked, &info->tcpi_bytes_acked);

	put_unaligned(tp->bytes_received, &info->tcpi_bytes_received);

	} while (u64_stats_fetch_retry_irq(&tp->syncp, start));

	info->tcpi_notsent_bytes = max_t(int, 0, tp->write_seq - tp->snd_nxt);



	unlock_sock_fast(sk, slow);



	info->tcpi_segs_out = tp->segs_out;

	info->tcpi_segs_in = tp->segs_in;



	notsent_bytes = READ_ONCE(tp->write_seq) - READ_ONCE(tp->snd_nxt);

	info->tcpi_notsent_bytes = max(0, notsent_bytes);



	info->tcpi_min_rtt = tcp_min_rtt(tp);

	info->tcpi_data_segs_in = tp->data_segs_in;

	info->tcpi_data_segs_out = tp->data_segs_out;

net/ipv4/tcp_input.c

+0 −4
Original line number Diff line number Diff line
@@ -3351,9 +3351,7 @@ static void tcp_snd_una_update(struct tcp_sock *tp, u32 ack) 
	u32 delta = ack - tp->snd_una;



	sock_owned_by_me((struct sock *)tp);

	u64_stats_update_begin_raw(&tp->syncp);

	tp->bytes_acked += delta;

	u64_stats_update_end_raw(&tp->syncp);

	tp->snd_una = ack;

}
@@ -3363,9 +3361,7 @@ static void tcp_rcv_nxt_update(struct tcp_sock *tp, u32 seq) 
	u32 delta = seq - tp->rcv_nxt;



	sock_owned_by_me((struct sock *)tp);

	u64_stats_update_begin_raw(&tp->syncp);

	tp->bytes_received += delta;

	u64_stats_update_end_raw(&tp->syncp);

	tp->rcv_nxt = seq;

}