diff options
| author | Eric Dumazet <eric.dumazet@gmail.com> | 2010-05-26 19:20:18 +0000 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2010-05-27 00:30:53 -0700 |
| commit | 8a74ad60a546b13bd1096b2a61a7a5c6fd9ae17c (patch) | |
| tree | 3110e7e59883597b5d0f617e8507e15b8f965f3f /net/core | |
| parent | a56635a56f2afb3d22d9ce07e8f8d69537416b2d (diff) | |
net: fix lock_sock_bh/unlock_sock_bh
This new sock lock primitive was introduced to speedup some user context
socket manipulation. But it is unsafe to protect two threads, one using
regular lock_sock/release_sock, one using lock_sock_bh/unlock_sock_bh
This patch changes lock_sock_bh to be careful against 'owned' state.
If owned is found to be set, we must take the slow path.
lock_sock_bh() now returns a boolean to say if the slow path was taken,
and this boolean is used at unlock_sock_bh time to call the appropriate
unlock function.
After this change, BH are either disabled or enabled during the
lock_sock_bh/unlock_sock_bh protected section. This might be misleading,
so we rename these functions to lock_sock_fast()/unlock_sock_fast().
Reported-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Tested-by: Anton Blanchard <anton@samba.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/core')
| -rw-r--r-- | net/core/datagram.c | 6 | ||||
| -rw-r--r-- | net/core/sock.c | 33 |
2 files changed, 37 insertions, 2 deletions
diff --git a/net/core/datagram.c b/net/core/datagram.c index e0097531417a..f5b6f43a4c2e 100644 --- a/net/core/datagram.c +++ b/net/core/datagram.c @@ -229,15 +229,17 @@ EXPORT_SYMBOL(skb_free_datagram); void skb_free_datagram_locked(struct sock *sk, struct sk_buff *skb) { + bool slow; + if (likely(atomic_read(&skb->users) == 1)) smp_rmb(); else if (likely(!atomic_dec_and_test(&skb->users))) return; - lock_sock_bh(sk); + slow = lock_sock_fast(sk); skb_orphan(skb); sk_mem_reclaim_partial(sk); - unlock_sock_bh(sk); + unlock_sock_fast(sk, slow); /* skb is now orphaned, can be freed outside of locked section */ __kfree_skb(skb); diff --git a/net/core/sock.c b/net/core/sock.c index 37fe9b6adade..2cf7f9f7e775 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -2007,6 +2007,39 @@ void release_sock(struct sock *sk) } EXPORT_SYMBOL(release_sock); +/** + * lock_sock_fast - fast version of lock_sock + * @sk: socket + * + * This version should be used for very small section, where process wont block + * return false if fast path is taken + * sk_lock.slock locked, owned = 0, BH disabled + * return true if slow path is taken + * sk_lock.slock unlocked, owned = 1, BH enabled + */ +bool lock_sock_fast(struct sock *sk) +{ + might_sleep(); + spin_lock_bh(&sk->sk_lock.slock); + + if (!sk->sk_lock.owned) + /* + * Note : We must disable BH + */ + return false; + + __lock_sock(sk); + sk->sk_lock.owned = 1; + spin_unlock(&sk->sk_lock.slock); + /* + * The sk_lock has mutex_lock() semantics here: + */ + mutex_acquire(&sk->sk_lock.dep_map, 0, 0, _RET_IP_); + local_bh_enable(); + return true; +} +EXPORT_SYMBOL(lock_sock_fast); + int sock_get_timestamp(struct sock *sk, struct timeval __user *userstamp) { struct timeval tv; |