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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 <penguin-kernel@I-love.SAKURA.ne.jp>
Tested-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
CC: Jarek Poplawski <jarkao2@gmail.com>
Tested-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Eric Dumazet authored and David S. Miller committed Sep 25, 2010
1 parent 605c82b commit f064af1
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Showing 6 changed files with 26 additions and 26 deletions.
8 changes: 4 additions & 4 deletions net/core/sock.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1351,9 +1351,9 @@ int sock_i_uid(struct sock *sk)
{
int uid;

read_lock(&sk->sk_callback_lock);
read_lock_bh(&sk->sk_callback_lock);
uid = sk->sk_socket ? SOCK_INODE(sk->sk_socket)->i_uid : 0;
read_unlock(&sk->sk_callback_lock);
read_unlock_bh(&sk->sk_callback_lock);
return uid;
}
EXPORT_SYMBOL(sock_i_uid);
Expand All @@ -1362,9 +1362,9 @@ unsigned long sock_i_ino(struct sock *sk)
{
unsigned long ino;

read_lock(&sk->sk_callback_lock);
read_lock_bh(&sk->sk_callback_lock);
ino = sk->sk_socket ? SOCK_INODE(sk->sk_socket)->i_ino : 0;
read_unlock(&sk->sk_callback_lock);
read_unlock_bh(&sk->sk_callback_lock);
return ino;
}
EXPORT_SYMBOL(sock_i_ino);
Expand Down
4 changes: 2 additions & 2 deletions net/rds/tcp_connect.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -43,7 +43,7 @@ void rds_tcp_state_change(struct sock *sk)
struct rds_connection *conn;
struct rds_tcp_connection *tc;

read_lock(&sk->sk_callback_lock);
read_lock_bh(&sk->sk_callback_lock);
conn = sk->sk_user_data;
if (conn == NULL) {
state_change = sk->sk_state_change;
Expand All @@ -68,7 +68,7 @@ void rds_tcp_state_change(struct sock *sk)
break;
}
out:
read_unlock(&sk->sk_callback_lock);
read_unlock_bh(&sk->sk_callback_lock);
state_change(sk);
}

Expand Down
4 changes: 2 additions & 2 deletions net/rds/tcp_listen.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -114,7 +114,7 @@ void rds_tcp_listen_data_ready(struct sock *sk, int bytes)

rdsdebug("listen data ready sk %p\n", sk);

read_lock(&sk->sk_callback_lock);
read_lock_bh(&sk->sk_callback_lock);
ready = sk->sk_user_data;
if (ready == NULL) { /* check for teardown race */
ready = sk->sk_data_ready;
Expand All @@ -131,7 +131,7 @@ void rds_tcp_listen_data_ready(struct sock *sk, int bytes)
queue_work(rds_wq, &rds_tcp_listen_work);

out:
read_unlock(&sk->sk_callback_lock);
read_unlock_bh(&sk->sk_callback_lock);
ready(sk, bytes);
}

Expand Down
4 changes: 2 additions & 2 deletions net/rds/tcp_recv.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -324,7 +324,7 @@ void rds_tcp_data_ready(struct sock *sk, int bytes)

rdsdebug("data ready sk %p bytes %d\n", sk, bytes);

read_lock(&sk->sk_callback_lock);
read_lock_bh(&sk->sk_callback_lock);
conn = sk->sk_user_data;
if (conn == NULL) { /* check for teardown race */
ready = sk->sk_data_ready;
Expand All @@ -338,7 +338,7 @@ void rds_tcp_data_ready(struct sock *sk, int bytes)
if (rds_tcp_read_sock(conn, GFP_ATOMIC, KM_SOFTIRQ0) == -ENOMEM)
queue_delayed_work(rds_wq, &conn->c_recv_w, 0);
out:
read_unlock(&sk->sk_callback_lock);
read_unlock_bh(&sk->sk_callback_lock);
ready(sk, bytes);
}

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4 changes: 2 additions & 2 deletions net/rds/tcp_send.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -224,7 +224,7 @@ void rds_tcp_write_space(struct sock *sk)
struct rds_connection *conn;
struct rds_tcp_connection *tc;

read_lock(&sk->sk_callback_lock);
read_lock_bh(&sk->sk_callback_lock);
conn = sk->sk_user_data;
if (conn == NULL) {
write_space = sk->sk_write_space;
Expand All @@ -244,7 +244,7 @@ void rds_tcp_write_space(struct sock *sk)
queue_delayed_work(rds_wq, &conn->c_send_w, 0);

out:
read_unlock(&sk->sk_callback_lock);
read_unlock_bh(&sk->sk_callback_lock);

/*
* write_space is only called when data leaves tcp's send queue if
Expand Down
28 changes: 14 additions & 14 deletions net/sunrpc/xprtsock.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand Down Expand Up @@ -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)
Expand Down Expand Up @@ -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)
Expand All @@ -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);
}

/*
Expand Down Expand Up @@ -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);
Expand All @@ -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);
Expand All @@ -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 */
Expand Down Expand Up @@ -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);
}

/**
Expand All @@ -1376,15 +1376,15 @@ 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"
"RPC: error %d\n",
__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)
Expand Down Expand Up @@ -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);
}

/**
Expand All @@ -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)
Expand Down

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