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tcp_metrics: annotate data-races around tm->tcpm_stamp

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[ Upstream commit 949ad62a5d ]

tm->tcpm_stamp can be read or written locklessly.

Add needed READ_ONCE()/WRITE_ONCE() to document this.

Also constify tcpm_check_stamp() dst argument.

Fixes: 51c5d0c4b1 ("tcp: Maintain dynamic metrics in local cache.")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://lore.kernel.org/r/20230802131500.1478140-3-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Eric Dumazet 2023-08-02 13:14:56 +00:00 committed by Greg Kroah-Hartman
parent 71f891a254
commit 4a77a0f752
1 changed files with 13 additions and 6 deletions
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19
net/ipv4/tcp_metrics.c
View file

@ -97,7 +97,7 @@ static void tcpm_suck_dst(struct tcp_metrics_block *tm,
u32 msval; u32 msval;
u32 val; u32 val;
tm->tcpm_stamp = jiffies; WRITE_ONCE(tm->tcpm_stamp, jiffies);
val = 0; val = 0;
if (dst_metric_locked(dst, RTAX_RTT)) if (dst_metric_locked(dst, RTAX_RTT))
@ -131,9 +131,15 @@ static void tcpm_suck_dst(struct tcp_metrics_block *tm,
#define TCP_METRICS_TIMEOUT (60 * 60 * HZ) #define TCP_METRICS_TIMEOUT (60 * 60 * HZ)
static void tcpm_check_stamp(struct tcp_metrics_block *tm, struct dst_entry *dst) static void tcpm_check_stamp(struct tcp_metrics_block *tm,
const struct dst_entry *dst)
{ {
if (tm && unlikely(time_after(jiffies, tm->tcpm_stamp + TCP_METRICS_TIMEOUT))) unsigned long limit;
if (!tm)
return;
limit = READ_ONCE(tm->tcpm_stamp) + TCP_METRICS_TIMEOUT;
if (unlikely(time_after(jiffies, limit)))
tcpm_suck_dst(tm, dst, false); tcpm_suck_dst(tm, dst, false);
} }
@ -174,7 +180,8 @@ static struct tcp_metrics_block *tcpm_new(struct dst_entry *dst,
oldest = deref_locked(tcp_metrics_hash[hash].chain); oldest = deref_locked(tcp_metrics_hash[hash].chain);
for (tm = deref_locked(oldest->tcpm_next); tm; for (tm = deref_locked(oldest->tcpm_next); tm;
tm = deref_locked(tm->tcpm_next)) { tm = deref_locked(tm->tcpm_next)) {
if (time_before(tm->tcpm_stamp, oldest->tcpm_stamp)) if (time_before(READ_ONCE(tm->tcpm_stamp),
READ_ONCE(oldest->tcpm_stamp)))
oldest = tm; oldest = tm;
} }
tm = oldest; tm = oldest;
@ -434,7 +441,7 @@ void tcp_update_metrics(struct sock *sk)
tp->reordering); tp->reordering);
} }
} }
tm->tcpm_stamp = jiffies; WRITE_ONCE(tm->tcpm_stamp, jiffies);
out_unlock: out_unlock:
rcu_read_unlock(); rcu_read_unlock();
} }
@ -647,7 +654,7 @@ static int tcp_metrics_fill_info(struct sk_buff *msg,
} }
if (nla_put_msecs(msg, TCP_METRICS_ATTR_AGE, if (nla_put_msecs(msg, TCP_METRICS_ATTR_AGE,
jiffies - tm->tcpm_stamp, jiffies - READ_ONCE(tm->tcpm_stamp),
TCP_METRICS_ATTR_PAD) < 0) TCP_METRICS_ATTR_PAD) < 0)
goto nla_put_failure; goto nla_put_failure;