From f3f05f7046e7c85b04af390d95a82a27160dd5d0 Mon Sep 17 00:00:00 2001 From: Arnaldo Carvalho de Melo Date: Tue, 9 Aug 2005 20:08:09 -0700 Subject: [INET]: Generalise the tcp_listen_ lock routines Signed-off-by: Arnaldo Carvalho de Melo Signed-off-by: David S. Miller --- net/ipv4/inet_hashtables.c | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) (limited to 'net/ipv4/inet_hashtables.c') diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c index 33d6cbe32cdc..06cbc6f689c5 100644 --- a/net/ipv4/inet_hashtables.c +++ b/net/ipv4/inet_hashtables.c @@ -15,7 +15,9 @@ #include #include +#include #include +#include #include @@ -89,3 +91,33 @@ void inet_put_port(struct inet_hashinfo *hashinfo, struct sock *sk) } EXPORT_SYMBOL(inet_put_port); + +/* + * This lock without WQ_FLAG_EXCLUSIVE is good on UP and it can be very bad on SMP. + * Look, when several writers sleep and reader wakes them up, all but one + * immediately hit write lock and grab all the cpus. Exclusive sleep solves + * this, _but_ remember, it adds useless work on UP machines (wake up each + * exclusive lock release). It should be ifdefed really. + */ +void inet_listen_wlock(struct inet_hashinfo *hashinfo) +{ + write_lock(&hashinfo->lhash_lock); + + if (atomic_read(&hashinfo->lhash_users)) { + DEFINE_WAIT(wait); + + for (;;) { + prepare_to_wait_exclusive(&hashinfo->lhash_wait, + &wait, TASK_UNINTERRUPTIBLE); + if (!atomic_read(&hashinfo->lhash_users)) + break; + write_unlock_bh(&hashinfo->lhash_lock); + schedule(); + write_lock_bh(&hashinfo->lhash_lock); + } + + finish_wait(&hashinfo->lhash_wait, &wait); + } +} + +EXPORT_SYMBOL(inet_listen_wlock); -- cgit v1.2.3