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net: fix a lockdep splat

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We have for each socket :

One spinlock (sk_slock.slock)
One rwlock (sk_callback_lock)

Possible scenarios are :

(A) (this is used in net/sunrpc/xprtsock.c)
read_lock(&sk->sk_callback_lock) (without blocking BH)
<BH>
spin_lock(&sk->sk_slock.slock);
...
read_lock(&sk->sk_callback_lock);
...

(B)
write_lock_bh(&sk->sk_callback_lock)
stuff
write_unlock_bh(&sk->sk_callback_lock)

(C)
spin_lock_bh(&sk->sk_slock)
...
write_lock_bh(&sk->sk_callback_lock)
stuff
write_unlock_bh(&sk->sk_callback_lock)
spin_unlock_bh(&sk->sk_slock)

This (C) case conflicts with (A) :

CPU1 [A]                         CPU2 [C]
read_lock(callback_lock)
<BH>                             spin_lock_bh(slock)
<wait to spin_lock(slock)>
                                 <wait to write_lock_bh(callback_lock)>

We have one problematic (C) use case in inet_csk_listen_stop() :

local_bh_disable();
bh_lock_sock(child); // spin_lock_bh(&sk->sk_slock)
WARN_ON(sock_owned_by_user(child));
...
sock_orphan(child); // write_lock_bh(&sk->sk_callback_lock)

lockdep is not happy with this, as reported by Tetsuo Handa

It seems only way to deal with this is to use read_lock_bh(callbacklock)
everywhere.

Thanks to Jarek for pointing a bug in my first attempt and suggesting
this solution.

Reported-by: Tetsuo Handa <[email protected]>
Tested-by: Tetsuo Handa <[email protected]>
Signed-off-by: Eric Dumazet <[email protected]>
CC: Jarek Poplawski <[email protected]>
Tested-by: Eric Dumazet <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
This commit is contained in:
Eric Dumazet 2010-09-22 12:43:39 +00:00 • committed by David S. Miller
commit f064af1e50
6 changed files with 26 additions and 26 deletions
Download patch file Download diff file Expand all files Collapse all files

28
net/sunrpc/xprtsock.c
View file

@ -800,7 +800,7 @@ static void xs_udp_data_ready(struct sock *sk, int len)
u32 _xid;
__be32 *xp;
read_lock(&sk->sk_callback_lock);
read_lock_bh(&sk->sk_callback_lock);
dprintk("RPC: xs_udp_data_ready...\n");
if (!(xprt = xprt_from_sock(sk)))
goto out;
@ -852,7 +852,7 @@ static void xs_udp_data_ready(struct sock *sk, int len)
dropit:
skb_free_datagram(sk, skb);
out:
read_unlock(&sk->sk_callback_lock);
read_unlock_bh(&sk->sk_callback_lock);
}
static inline void xs_tcp_read_fraghdr(struct rpc_xprt *xprt, struct xdr_skb_reader *desc)
@ -1229,7 +1229,7 @@ static void xs_tcp_data_ready(struct sock *sk, int bytes)
dprintk("RPC: xs_tcp_data_ready...\n");
read_lock(&sk->sk_callback_lock);
read_lock_bh(&sk->sk_callback_lock);
if (!(xprt = xprt_from_sock(sk)))
goto out;
if (xprt->shutdown)
@ -1248,7 +1248,7 @@ static void xs_tcp_data_ready(struct sock *sk, int bytes)
read = tcp_read_sock(sk, &rd_desc, xs_tcp_data_recv);
} while (read > 0);
out:
read_unlock(&sk->sk_callback_lock);
read_unlock_bh(&sk->sk_callback_lock);
}
/*
@ -1301,7 +1301,7 @@ static void xs_tcp_state_change(struct sock *sk)
{
struct rpc_xprt *xprt;
read_lock(&sk->sk_callback_lock);
read_lock_bh(&sk->sk_callback_lock);
if (!(xprt = xprt_from_sock(sk)))
goto out;
dprintk("RPC: xs_tcp_state_change client %p...\n", xprt);
@ -1313,7 +1313,7 @@ static void xs_tcp_state_change(struct sock *sk)
switch (sk->sk_state) {
case TCP_ESTABLISHED:
spin_lock_bh(&xprt->transport_lock);
spin_lock(&xprt->transport_lock);
if (!xprt_test_and_set_connected(xprt)) {
struct sock_xprt *transport = container_of(xprt,
struct sock_xprt, xprt);
@ -1327,7 +1327,7 @@ static void xs_tcp_state_change(struct sock *sk)
xprt_wake_pending_tasks(xprt, -EAGAIN);
}
spin_unlock_bh(&xprt->transport_lock);
spin_unlock(&xprt->transport_lock);
break;
case TCP_FIN_WAIT1:
/* The client initiated a shutdown of the socket */
@ -1365,7 +1365,7 @@ static void xs_tcp_state_change(struct sock *sk)
xs_sock_mark_closed(xprt);
}
out:
read_unlock(&sk->sk_callback_lock);
read_unlock_bh(&sk->sk_callback_lock);
}
/**
@ -1376,7 +1376,7 @@ static void xs_error_report(struct sock *sk)
{
struct rpc_xprt *xprt;
read_lock(&sk->sk_callback_lock);
read_lock_bh(&sk->sk_callback_lock);
if (!(xprt = xprt_from_sock(sk)))
goto out;
dprintk("RPC: %s client %p...\n"
@ -1384,7 +1384,7 @@ static void xs_error_report(struct sock *sk)
__func__, xprt, sk->sk_err);
xprt_wake_pending_tasks(xprt, -EAGAIN);
out:
read_unlock(&sk->sk_callback_lock);
read_unlock_bh(&sk->sk_callback_lock);
}
static void xs_write_space(struct sock *sk)
@ -1416,13 +1416,13 @@ static void xs_write_space(struct sock *sk)
*/
static void xs_udp_write_space(struct sock *sk)
{
read_lock(&sk->sk_callback_lock);
read_lock_bh(&sk->sk_callback_lock);
/* from net/core/sock.c:sock_def_write_space */
if (sock_writeable(sk))
xs_write_space(sk);
read_unlock(&sk->sk_callback_lock);
read_unlock_bh(&sk->sk_callback_lock);
}
/**
@ -1437,13 +1437,13 @@ static void xs_udp_write_space(struct sock *sk)
*/
static void xs_tcp_write_space(struct sock *sk)
{
read_lock(&sk->sk_callback_lock);
read_lock_bh(&sk->sk_callback_lock);
/* from net/core/stream.c:sk_stream_write_space */
if (sk_stream_wspace(sk) >= sk_stream_min_wspace(sk))
xs_write_space(sk);
read_unlock(&sk->sk_callback_lock);
read_unlock_bh(&sk->sk_callback_lock);
}
static void xs_udp_do_set_buffer_size(struct rpc_xprt *xprt)