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| author | Eric Dumazet <edumazet@google.com> | 2017-12-12 06:25:12 +0100 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2017-12-13 20:33:10 +0100 |
| commit | ec94c2696f0bcd5ae92a553244e4ac30d2171a2d (patch) | |
| tree | 1a9eebba8042da0292f583f778abbe72974cc2a2 /net/ipv4 | |
| parent | Merge branch 'rmnet-Configuration-options' (diff) | |
| download | linux-ec94c2696f0bcd5ae92a553244e4ac30d2171a2d.tar.xz linux-ec94c2696f0bcd5ae92a553244e4ac30d2171a2d.zip | |
tcp/dccp: avoid one atomic operation for timewait hashdance
First, rename __inet_twsk_hashdance() to inet_twsk_hashdance()
Then, remove one inet_twsk_put() by setting tw_refcnt to 3 instead
of 4, but adding a fat warning that we do not have the right to access
tw anymore after inet_twsk_hashdance()
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4')
| -rw-r--r-- | net/ipv4/inet_timewait_sock.c | 27 | ||||
| -rw-r--r-- | net/ipv4/tcp_minisocks.c | 7 |
2 files changed, 17 insertions, 17 deletions
diff --git a/net/ipv4/inet_timewait_sock.c b/net/ipv4/inet_timewait_sock.c index b563e0c46bac..277ff69a312d 100644 --- a/net/ipv4/inet_timewait_sock.c +++ b/net/ipv4/inet_timewait_sock.c @@ -97,7 +97,7 @@ static void inet_twsk_add_bind_node(struct inet_timewait_sock *tw, * Essentially we whip up a timewait bucket, copy the relevant info into it * from the SK, and mess with hash chains and list linkage. */ -void __inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk, +void inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk, struct inet_hashinfo *hashinfo) { const struct inet_sock *inet = inet_sk(sk); @@ -119,18 +119,6 @@ void __inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk, spin_lock(lock); - /* - * Step 2: Hash TW into tcp ehash chain. - * Notes : - * - tw_refcnt is set to 4 because : - * - We have one reference from bhash chain. - * - We have one reference from ehash chain. - * - We have one reference from timer. - * - One reference for ourself (our caller will release it). - * We can use atomic_set() because prior spin_lock()/spin_unlock() - * committed into memory all tw fields. - */ - refcount_set(&tw->tw_refcnt, 4); inet_twsk_add_node_rcu(tw, &ehead->chain); /* Step 3: Remove SK from hash chain */ @@ -138,8 +126,19 @@ void __inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk, sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1); spin_unlock(lock); + + /* tw_refcnt is set to 3 because we have : + * - one reference for bhash chain. + * - one reference for ehash chain. + * - one reference for timer. + * We can use atomic_set() because prior spin_lock()/spin_unlock() + * committed into memory all tw fields. + * Also note that after this point, we lost our implicit reference + * so we are not allowed to use tw anymore. + */ + refcount_set(&tw->tw_refcnt, 3); } -EXPORT_SYMBOL_GPL(__inet_twsk_hashdance); +EXPORT_SYMBOL_GPL(inet_twsk_hashdance); static void tw_timer_handler(struct timer_list *t) { diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c index b079b619b60c..a8384b0c11f8 100644 --- a/net/ipv4/tcp_minisocks.c +++ b/net/ipv4/tcp_minisocks.c @@ -316,9 +316,10 @@ void tcp_time_wait(struct sock *sk, int state, int timeo) */ local_bh_disable(); inet_twsk_schedule(tw, timeo); - /* Linkage updates. */ - __inet_twsk_hashdance(tw, sk, &tcp_hashinfo); - inet_twsk_put(tw); + /* Linkage updates. + * Note that access to tw after this point is illegal. + */ + inet_twsk_hashdance(tw, sk, &tcp_hashinfo); local_bh_enable(); } else { /* Sorry, if we're out of memory, just CLOSE this |