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net: fix lock_sock_bh/unlock_sock_bh

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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>
This commit is contained in:
Eric Dumazet 2010-05-26 19:20:18 +00:00 • committed by David S. Miller
parent a56635a56f
commit 8a74ad60a5
5 changed files with 62 additions and 16 deletions
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33
net/core/sock.c
View file

@ -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;