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Date: Fri, 4 Nov 2016 11:54:32 -0700
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>
Cc: netdev <netdev@...r.kernel.org>,
Neal Cardwell <ncardwell@...gle.com>,
Yuchung Cheng <ycheng@...gle.com>,
Soheil Hassas Yeganeh <soheil@...gle.com>,
Eric Dumazet <edumazet@...gle.com>,
Eric Dumazet <eric.dumazet@...il.com>
Subject: [PATCH net-next 2/2] 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 d654976cbf85
("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: Eric Dumazet <edumazet@...gle.com>
Signed-off-by: Yuchung Cheng <ycheng@...gle.com>
Acked-by: Soheil Hassas Yeganeh <soheil@...gle.com>
Acked-by: Neal Cardwell <ncardwell@...gle.com>
---
include/linux/tcp.h | 2 --
net/ipv4/inet_diag.c | 48 +++++++++++++++++++++++++++++++++---------------
net/ipv4/tcp.c | 20 +++++++++-----------
net/ipv4/tcp_input.c | 4 ----
4 files changed, 42 insertions(+), 32 deletions(-)
diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index a17ae7b85218..32a7c7e35b71 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -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) */
diff --git a/net/ipv4/inet_diag.c b/net/ipv4/inet_diag.c
index 3b34024202d8..4dea33e5f295 100644
--- a/net/ipv4/inet_diag.c
+++ b/net/ipv4/inet_diag.c
@@ -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:
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 117982be0cab..a7d54cbcdabb 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -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);
- 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));
+ slow = lock_sock_fast(sk);
+
+ put_unaligned(tp->bytes_acked, &info->tcpi_bytes_acked);
+ put_unaligned(tp->bytes_received, &info->tcpi_bytes_received);
+ 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;
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index f2c59c8e57ff..a70046fea0e8 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -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;
}
--
2.8.0.rc3.226.g39d4020
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