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@google.com>
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/inet_diag.c b/net/ipv4/inet_diag.c
index 3b34024..4dea33e 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)
{
- 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);
+ struct net *net = sock_net(skb->sk);
+ u32 idiag_states = r->idiag_states;
+ 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: