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Date: Mon, 08 Apr 2013 07:30:22 -0700
From: Eric Dumazet <eric.dumazet@...il.com>
To: Bjørn Mork <bjorn@...k.no>
Cc: Eric Dumazet <edumazet@...gle.com>, netdev@...r.kernel.org
Subject: Re: v3.8.5: "TCP: snd_cwnd is nul, please report this bug."
On Mon, 2013-04-08 at 11:06 +0200, Bjørn Mork wrote:
> Hello,
>
> I just got this message running a Debian experimental
> linux-image-3.8-trunk-amd64 kernel, currently based on v3.8.5.
>
> Peeked briefly through the commit adding the message, but I couldn't
> figure out what other info you'd need so please ask if there is anything
> I can dig up.
>
> I suspect the warning could be related to problems with the iwlwifi
> driver and/or access point. The message was immediately followed by a
> few messges from iwlwifi:
>
>
> Apr 8 10:58:09 nemi kernel: [152701.980799] TCP: snd_cwnd is nul, please report this bug.
> Apr 8 10:58:33 nemi kernel: [152725.176151] iwlwifi 0000:03:00.0: fail to flush all tx fifo queues
> Apr 8 10:58:33 nemi kernel: [152725.185713] wlan0: authenticate with 00:22:90:f9:23:a0
> Apr 8 10:58:33 nemi kernel: [152725.185738] wlan0: capabilities/regulatory prevented using AP HT/VHT configuration, downgraded
> Apr 8 10:58:33 nemi kernel: [152725.190150] wlan0: send auth to 00:22:90:f9:23:a0 (try 1/3)
> Apr 8 10:58:33 nemi kernel: [152725.199812] wlan0: authenticated
> Apr 8 10:58:33 nemi kernel: [152725.200020] iwlwifi 0000:03:00.0 wlan0: disabling HT as WMM/QoS is not supported by the AP
> Apr 8 10:58:33 nemi kernel: [152725.200027] iwlwifi 0000:03:00.0 wlan0: disabling VHT as WMM/QoS is not supported by the AP
> Apr 8 10:58:33 nemi kernel: [152725.204033] wlan0: associate with 00:22:90:f9:23:a0 (try 1/3)
> Apr 8 10:58:33 nemi kernel: [152725.207317] wlan0: RX AssocResp from 00:22:90:f9:23:a0 (capab=0x421 status=0 aid=12)
> Apr 8 10:58:33 nemi kernel: [152725.210745] wlan0: associated
>
Same issue was reported by Dave Jones on iwlwifi few days ago and I sent
following debugging patch, could you try it ?
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 4475aaf..e2e89aa 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -609,6 +609,14 @@ static inline u32 __tcp_set_rto(const struct tcp_sock *tp)
extern void tcp_set_rto(struct sock *sk);
+extern void tcp_snd_cwnd_bad(const struct tcp_sock *tp);
+static inline void tcp_snd_cwnd_set(struct tcp_sock *tp, u32 newval)
+{
+ if (unlikely(!newval))
+ tcp_snd_cwnd_bad(tp);
+ tp->snd_cwnd = newval;
+}
+
static inline void __tcp_fast_path_on(struct tcp_sock *tp, u32 snd_wnd)
{
tp->pred_flags = htonl((tp->tcp_header_len << 26) |
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index a96f7b5..4347e22 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3300,6 +3300,33 @@ void tcp_done(struct sock *sk)
}
EXPORT_SYMBOL_GPL(tcp_done);
+void tcp_snd_cwnd_bad(const struct tcp_sock *tp)
+{
+ static bool warned = false;
+
+ if (!warned) {
+ const struct sock *sk = (struct sock *)tp;
+ const struct inet_sock *inet = inet_sk(sk);
+
+ warned = true;
+ if (sk->sk_family == AF_INET)
+ pr_err("TCP: zero snd_cwnd src:%pI4.%u dst:%pI4.%u\n",
+ &inet->inet_saddr, ntohs(inet->inet_sport),
+ &inet->inet_daddr, ntohs(inet->inet_dport));
+#if IS_ENABLED(CONFIG_IPV6)
+ else if (sk->sk_family == AF_INET6) {
+ const struct ipv6_pinfo *np = inet6_sk(sk);
+
+ pr_err("TCP: zero snd_cwnd src:%pI6.%u dst:%pI6.%u\n",
+ &np->saddr, ntohs(inet->inet_sport),
+ &np->daddr, ntohs(inet->inet_dport));
+ }
+#endif
+ WARN_ON_ONCE(1);
+ }
+}
+EXPORT_SYMBOL(tcp_snd_cwnd_bad);
+
extern struct tcp_congestion_ops tcp_reno;
static __initdata unsigned long thash_entries;
diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c
index 019c238..6ddd167 100644
--- a/net/ipv4/tcp_cong.c
+++ b/net/ipv4/tcp_cong.c
@@ -327,7 +327,7 @@ void tcp_slow_start(struct tcp_sock *tp)
tp->snd_cwnd_cnt -= snd_cwnd;
delta++;
}
- tp->snd_cwnd = min(snd_cwnd + delta, tp->snd_cwnd_clamp);
+ tcp_snd_cwnd_set(tp, min(snd_cwnd + delta, tp->snd_cwnd_clamp));
}
EXPORT_SYMBOL_GPL(tcp_slow_start);
diff --git a/net/ipv4/tcp_hybla.c b/net/ipv4/tcp_hybla.c
index 57bdd17..d236b70 100644
--- a/net/ipv4/tcp_hybla.c
+++ b/net/ipv4/tcp_hybla.c
@@ -60,7 +60,7 @@ static void hybla_init(struct sock *sk)
/* set minimum rtt as this is the 1st ever seen */
ca->minrtt = tp->srtt;
- tp->snd_cwnd = ca->rho;
+ tcp_snd_cwnd_set(tp, ca->rho);
}
static void hybla_state(struct sock *sk, u8 ca_state)
@@ -157,9 +157,9 @@ static void hybla_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
}
/* clamp down slowstart cwnd to ssthresh value. */
if (is_slowstart)
- tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
+ tcp_snd_cwnd_set(tp, min(tp->snd_cwnd, tp->snd_ssthresh));
- tp->snd_cwnd = min_t(u32, tp->snd_cwnd, tp->snd_cwnd_clamp);
+ tcp_snd_cwnd_set(tp, min_t(u32, tp->snd_cwnd, tp->snd_cwnd_clamp));
}
static struct tcp_congestion_ops tcp_hybla __read_mostly = {
diff --git a/net/ipv4/tcp_illinois.c b/net/ipv4/tcp_illinois.c
index 834857f..71135e3 100644
--- a/net/ipv4/tcp_illinois.c
+++ b/net/ipv4/tcp_illinois.c
@@ -284,8 +284,9 @@ static void tcp_illinois_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
*/
delta = (tp->snd_cwnd_cnt * ca->alpha) >> ALPHA_SHIFT;
if (delta >= tp->snd_cwnd) {
- tp->snd_cwnd = min(tp->snd_cwnd + delta / tp->snd_cwnd,
- (u32) tp->snd_cwnd_clamp);
+ tcp_snd_cwnd_set(tp,
+ min(tp->snd_cwnd + delta / tp->snd_cwnd,
+ (u32) tp->snd_cwnd_clamp));
tp->snd_cwnd_cnt = 0;
}
}
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 6d9ca35..b972577 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2259,8 +2259,8 @@ static void tcp_update_scoreboard(struct sock *sk, int fast_rexmit)
*/
static inline void tcp_moderate_cwnd(struct tcp_sock *tp)
{
- tp->snd_cwnd = min(tp->snd_cwnd,
- tcp_packets_in_flight(tp) + tcp_max_burst(tp));
+ tcp_snd_cwnd_set(tp, min(tp->snd_cwnd,
+ tcp_packets_in_flight(tp) + tcp_max_burst(tp)));
tp->snd_cwnd_stamp = tcp_time_stamp;
}
@@ -2312,18 +2312,20 @@ static void tcp_undo_cwr(struct sock *sk, const bool undo_ssthresh)
if (tp->prior_ssthresh) {
const struct inet_connection_sock *icsk = inet_csk(sk);
+ u32 newval;
if (icsk->icsk_ca_ops->undo_cwnd)
- tp->snd_cwnd = icsk->icsk_ca_ops->undo_cwnd(sk);
+ newval = icsk->icsk_ca_ops->undo_cwnd(sk);
else
- tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh << 1);
+ newval = max(tp->snd_cwnd, tp->snd_ssthresh << 1);
+ tcp_snd_cwnd_set(tp, newval);
if (undo_ssthresh && tp->prior_ssthresh > tp->snd_ssthresh) {
tp->snd_ssthresh = tp->prior_ssthresh;
TCP_ECN_withdraw_cwr(tp);
}
} else {
- tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh);
+ tcp_snd_cwnd_set(tp, max(tp->snd_cwnd, tp->snd_ssthresh));
}
tp->snd_cwnd_stamp = tcp_time_stamp;
}
@@ -2512,7 +2514,7 @@ static void tcp_cwnd_reduction(struct sock *sk, int newly_acked_sacked,
}
sndcnt = max(sndcnt, (fast_rexmit ? 1 : 0));
- tp->snd_cwnd = tcp_packets_in_flight(tp) + sndcnt;
+ tcp_snd_cwnd_set(tp, tcp_packets_in_flight(tp) + sndcnt);
}
static inline void tcp_end_cwnd_reduction(struct sock *sk)
@@ -2522,7 +2524,7 @@ static inline void tcp_end_cwnd_reduction(struct sock *sk)
/* Reset cwnd to ssthresh in CWR or Recovery (unless it's undone) */
if (inet_csk(sk)->icsk_ca_state == TCP_CA_CWR ||
(tp->undo_marker && tp->snd_ssthresh < TCP_INFINITE_SSTHRESH)) {
- tp->snd_cwnd = tp->snd_ssthresh;
+ tcp_snd_cwnd_set(tp, tp->snd_ssthresh);
tp->snd_cwnd_stamp = tcp_time_stamp;
}
tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR);
@@ -2591,9 +2593,9 @@ static void tcp_mtup_probe_success(struct sock *sk)
/* FIXME: breaks with very large cwnd */
tp->prior_ssthresh = tcp_current_ssthresh(sk);
- tp->snd_cwnd = tp->snd_cwnd *
- tcp_mss_to_mtu(sk, tp->mss_cache) /
- icsk->icsk_mtup.probe_size;
+ tcp_snd_cwnd_set(tp, tp->snd_cwnd *
+ tcp_mss_to_mtu(sk, tp->mss_cache) /
+ icsk->icsk_mtup.probe_size);
tp->snd_cwnd_cnt = 0;
tp->snd_cwnd_stamp = tcp_time_stamp;
tp->snd_ssthresh = tcp_current_ssthresh(sk);
@@ -4665,7 +4667,7 @@ void tcp_cwnd_application_limited(struct sock *sk)
u32 win_used = max(tp->snd_cwnd_used, init_win);
if (win_used < tp->snd_cwnd) {
tp->snd_ssthresh = tcp_current_ssthresh(sk);
- tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1;
+ tcp_snd_cwnd_set(tp, (tp->snd_cwnd + win_used) >> 1);
}
tp->snd_cwnd_used = 0;
}
diff --git a/net/ipv4/tcp_lp.c b/net/ipv4/tcp_lp.c
index 72f7218..09bf418 100644
--- a/net/ipv4/tcp_lp.c
+++ b/net/ipv4/tcp_lp.c
@@ -307,7 +307,7 @@ static void tcp_lp_pkts_acked(struct sock *sk, u32 num_acked, s32 rtt_us)
/* happened after inference
* cut snd_cwnd into half */
else
- tp->snd_cwnd = max(tp->snd_cwnd >> 1U, 1U);
+ tcp_snd_cwnd_set(tp, max(tp->snd_cwnd >> 1U, 1U));
/* record this drop time */
lp->last_drop = tcp_time_stamp;
diff --git a/net/ipv4/tcp_metrics.c b/net/ipv4/tcp_metrics.c
index f696d7c..d5a6608 100644
--- a/net/ipv4/tcp_metrics.c
+++ b/net/ipv4/tcp_metrics.c
@@ -526,7 +526,7 @@ reset:
if (tp->total_retrans > 1)
tp->snd_cwnd = 1;
else
- tp->snd_cwnd = tcp_init_cwnd(tp, dst);
+ tcp_snd_cwnd_set(tp, tcp_init_cwnd(tp, dst));
tp->snd_cwnd_stamp = tcp_time_stamp;
}
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index af354c98..2b80083 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -148,7 +148,7 @@ static void tcp_cwnd_restart(struct sock *sk, const struct dst_entry *dst)
while ((delta -= inet_csk(sk)->icsk_rto) > 0 && cwnd > restart_cwnd)
cwnd >>= 1;
- tp->snd_cwnd = max(cwnd, restart_cwnd);
+ tcp_snd_cwnd_set(tp, max(cwnd, restart_cwnd));
tp->snd_cwnd_stamp = tcp_time_stamp;
tp->snd_cwnd_used = 0;
}
diff --git a/net/ipv4/tcp_vegas.c b/net/ipv4/tcp_vegas.c
index 80fa2bf..a270cf9 100644
--- a/net/ipv4/tcp_vegas.c
+++ b/net/ipv4/tcp_vegas.c
@@ -238,7 +238,8 @@ static void tcp_vegas_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
* truncation robs us of full link
* utilization.
*/
- tp->snd_cwnd = min(tp->snd_cwnd, (u32)target_cwnd+1);
+ tcp_snd_cwnd_set(tp, min(tp->snd_cwnd,
+ (u32)target_cwnd + 1));
tp->snd_ssthresh = tcp_vegas_ssthresh(tp);
} else if (tp->snd_cwnd <= tp->snd_ssthresh) {
@@ -272,7 +273,7 @@ static void tcp_vegas_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
if (tp->snd_cwnd < 2)
tp->snd_cwnd = 2;
else if (tp->snd_cwnd > tp->snd_cwnd_clamp)
- tp->snd_cwnd = tp->snd_cwnd_clamp;
+ tcp_snd_cwnd_set(tp, tp->snd_cwnd_clamp);
tp->snd_ssthresh = tcp_current_ssthresh(sk);
}
diff --git a/net/ipv4/tcp_veno.c b/net/ipv4/tcp_veno.c
index ac43cd7..d1fa5c1 100644
--- a/net/ipv4/tcp_veno.c
+++ b/net/ipv4/tcp_veno.c
@@ -180,7 +180,7 @@ static void tcp_veno_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
if (tp->snd_cwnd < 2)
tp->snd_cwnd = 2;
else if (tp->snd_cwnd > tp->snd_cwnd_clamp)
- tp->snd_cwnd = tp->snd_cwnd_clamp;
+ tcp_snd_cwnd_set(tp, tp->snd_cwnd_clamp);
}
/* Wipe the slate clean for the next rtt. */
/* veno->cntrtt = 0; */
diff --git a/net/ipv4/tcp_westwood.c b/net/ipv4/tcp_westwood.c
index 76a1e23..060fbb5 100644
--- a/net/ipv4/tcp_westwood.c
+++ b/net/ipv4/tcp_westwood.c
@@ -233,7 +233,8 @@ static void tcp_westwood_event(struct sock *sk, enum tcp_ca_event event)
break;
case CA_EVENT_COMPLETE_CWR:
- tp->snd_cwnd = tp->snd_ssthresh = tcp_westwood_bw_rttmin(sk);
+ tp->snd_ssthresh = tcp_westwood_bw_rttmin(sk);
+ tcp_snd_cwnd_set(tp, tp->snd_ssthresh);
break;
case CA_EVENT_LOSS:
diff --git a/net/ipv4/tcp_yeah.c b/net/ipv4/tcp_yeah.c
index 05c3b6f..3ad1dbb 100644
--- a/net/ipv4/tcp_yeah.c
+++ b/net/ipv4/tcp_yeah.c
@@ -161,11 +161,9 @@ static void tcp_yeah_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
tp->snd_cwnd > yeah->reno_count) {
u32 reduction = min(queue / TCP_YEAH_GAMMA ,
tp->snd_cwnd >> TCP_YEAH_EPSILON);
+ u32 tmp = tp->snd_cwnd - reduction;
- tp->snd_cwnd -= reduction;
-
- tp->snd_cwnd = max(tp->snd_cwnd,
- yeah->reno_count);
+ tcp_snd_cwnd_set(tp, max(tmp, yeah->reno_count));
tp->snd_ssthresh = tp->snd_cwnd;
}
--
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