From d5d283751ef3c05b6766501a46800cbee84959d6 Mon Sep 17 00:00:00 2001 From: "David S. Miller" Date: Tue, 23 Aug 2005 10:49:54 -0700 Subject: [PATCH] [TCP]: Document non-trivial locking path in tcp_v{4,6}_get_port(). This trips up a lot of folks reading this code. Put an unlikely() around the port-exhaustion test for good measure. Signed-off-by: David S. Miller --- net/ipv4/tcp_ipv4.c | 9 +++++++-- net/ipv6/tcp_ipv6.c | 9 +++++++-- 2 files changed, 14 insertions(+), 4 deletions(-) diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index 5d91213d34c0..67c670886c1f 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -242,9 +242,14 @@ static int tcp_v4_get_port(struct sock *sk, unsigned short snum) tcp_port_rover = rover; spin_unlock(&tcp_portalloc_lock); - /* Exhausted local port range during search? */ + /* Exhausted local port range during search? It is not + * possible for us to be holding one of the bind hash + * locks if this test triggers, because if 'remaining' + * drops to zero, we broke out of the do/while loop at + * the top level, not from the 'break;' statement. + */ ret = 1; - if (remaining <= 0) + if (unlikely(remaining <= 0)) goto fail; /* OK, here is the one we will use. HEAD is diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c index f6e288dc116e..ef29cfd936d3 100644 --- a/net/ipv6/tcp_ipv6.c +++ b/net/ipv6/tcp_ipv6.c @@ -158,9 +158,14 @@ static int tcp_v6_get_port(struct sock *sk, unsigned short snum) tcp_port_rover = rover; spin_unlock(&tcp_portalloc_lock); - /* Exhausted local port range during search? */ + /* Exhausted local port range during search? It is not + * possible for us to be holding one of the bind hash + * locks if this test triggers, because if 'remaining' + * drops to zero, we broke out of the do/while loop at + * the top level, not from the 'break;' statement. + */ ret = 1; - if (remaining <= 0) + if (unlikely(remaining <= 0)) goto fail; /* OK, here is the one we will use. */