[PATCH net-next 06/10] net/smc: no socket state changes in tasklet context

Ursula Braun
2017-04-10T12:58:01Z

Several state changes occur during SMC socket closing. Currently
state changes triggered locally occur in process context with
lock_sock() taken while state changes triggered by peer occur in
tasklet context with bh_lock_sock() taken. bh_lock_sock() does not
wait till a lock_sock(() task in process context is finished. This
may lead to races in socket state transitions resulting in dangling
SMC-sockets, or it may lead to duplicate SMC socket freeing.
This patch introduces a closing worker to run all state changes under
lock_sock().

Signed-off-by: Ursula Braun <ubraun@linux.vnet.ibm.com>
Reviewed-by: Thomas Richter <tmricht@linux.vnet.ibm.com>
Reported-by: Dave Jones <davej@codemonkey.org.uk>
---
net/smc/af_smc.c | 8 ++++++--
net/smc/smc.h | 1 +
net/smc/smc_cdc.c | 9 +++++++--
net/smc/smc_close.c | 39 +++++++++++++++++++++++++--------------
net/smc/smc_close.h | 2 +-
net/smc/smc_core.c | 2 +-
6 files changed, 41 insertions(+), 20 deletions(-)

diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index 0938037..3b7eda6 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -451,6 +451,9 @@ static int smc_connect_rdma(struct smc_sock *smc)
goto decline_rdma_unlock;
}

+ smc_close_init(smc);
+ smc_rx_init(smc);
+
if (local_contact == SMC_FIRST_CONTACT) {
rc = smc_ib_ready_link(link);
if (rc) {
@@ -477,7 +480,6 @@ static int smc_connect_rdma(struct smc_sock *smc)

mutex_unlock(&smc_create_lgr_pending);
smc_tx_init(smc);
- smc_rx_init(smc);

out_connected:
smc_copy_sock_settings_to_clc(smc);
@@ -800,6 +802,9 @@ static void smc_listen_work(struct work_struct *work)
goto decline_rdma;
}

+ smc_close_init(new_smc);
+ smc_rx_init(new_smc);
+
rc = smc_clc_send_accept(new_smc, local_contact);
if (rc)
goto out_err;
@@ -839,7 +844,6 @@ static void smc_listen_work(struct work_struct *work)
}

smc_tx_init(new_smc);
- smc_rx_init(new_smc);

out_connected:
sk_refcnt_debug_inc(newsmcsk);
diff --git a/net/smc/smc.h b/net/smc/smc.h
index ee5fbea..6e44313e 100644
--- a/net/smc/smc.h
+++ b/net/smc/smc.h
@@ -164,6 +164,7 @@ struct smc_connection {
#ifndef KERNEL_HAS_ATOMIC64
spinlock_t acurs_lock; /* protect cursors */
#endif
+ struct work_struct close_work; /* peer sent some closing */
};

struct smc_sock { /* smc sock container */
diff --git a/net/smc/smc_cdc.c b/net/smc/smc_cdc.c
index 4c9c2f6..a7294ed 100644
--- a/net/smc/smc_cdc.c
+++ b/net/smc/smc_cdc.c
@@ -217,8 +217,13 @@ static void smc_cdc_msg_recv_action(struct smc_sock *smc,
smc->sk.sk_err = ECONNRESET;
conn->local_tx_ctrl.conn_state_flags.peer_conn_abort = 1;
}
- if (smc_cdc_rxed_any_close_or_senddone(conn))
- smc_close_passive_received(smc);
+ if (smc_cdc_rxed_any_close_or_senddone(conn)) {
+ smc->sk.sk_shutdown |= RCV_SHUTDOWN;
+ if (smc->clcsock && smc->clcsock->sk)
+ smc->clcsock->sk->sk_shutdown |= RCV_SHUTDOWN;
+ sock_set_flag(&smc->sk, SOCK_DONE);
+ schedule_work(&conn->close_work);
+ }

/* piggy backed tx info */
/* trigger sndbuf consumer: RDMA write into peer RMBE and CDC */
diff --git a/net/smc/smc_close.c b/net/smc/smc_close.c
index 67a71d1..388503b 100644
--- a/net/smc/smc_close.c
+++ b/net/smc/smc_close.c
@@ -117,7 +117,6 @@ void smc_close_active_abort(struct smc_sock *smc)
struct smc_cdc_conn_state_flags *txflags =
&smc->conn.local_tx_ctrl.conn_state_flags;

- bh_lock_sock(&smc->sk);
smc->sk.sk_err = ECONNABORTED;
if (smc->clcsock && smc->clcsock->sk) {
smc->clcsock->sk->sk_err = ECONNABORTED;
@@ -125,6 +124,7 @@ void smc_close_active_abort(struct smc_sock *smc)
}
switch (smc->sk.sk_state) {
case SMC_INIT:
+ case SMC_ACTIVE:
smc->sk.sk_state = SMC_PEERABORTWAIT;
break;
case SMC_APPCLOSEWAIT1:
@@ -161,7 +161,6 @@ void smc_close_active_abort(struct smc_sock *smc)
}

sock_set_flag(&smc->sk, SOCK_DEAD);
- bh_unlock_sock(&smc->sk);
smc->sk.sk_state_change(&smc->sk);
}

@@ -185,7 +184,7 @@ int smc_close_active(struct smc_sock *smc)
case SMC_INIT:
sk->sk_state = SMC_CLOSED;
if (smc->smc_listen_work.func)
- flush_work(&smc->smc_listen_work);
+ cancel_work_sync(&smc->smc_listen_work);
sock_put(sk);
break;
case SMC_LISTEN:
@@ -198,7 +197,7 @@ int smc_close_active(struct smc_sock *smc)
}
release_sock(sk);
smc_close_cleanup_listen(sk);
- flush_work(&smc->tcp_listen_work);
+ cancel_work_sync(&smc->smc_listen_work);
lock_sock(sk);
break;
case SMC_ACTIVE:
@@ -306,22 +305,27 @@ static void smc_close_passive_abort_received(struct smc_sock *smc)

/* Some kind of closing has been received: peer_conn_closed, peer_conn_abort,
* or peer_done_writing.
- * Called under tasklet context.
*/
-void smc_close_passive_received(struct smc_sock *smc)
+static void smc_close_passive_work(struct work_struct *work)
{
- struct smc_cdc_conn_state_flags *rxflags =
- &smc->conn.local_rx_ctrl.conn_state_flags;
+ struct smc_connection *conn = container_of(work,
+ struct smc_connection,
+ close_work);
+ struct smc_sock *smc = container_of(conn, struct smc_sock, conn);
+ struct smc_cdc_conn_state_flags *rxflags;
struct sock *sk = &smc->sk;
int old_state;

- sk->sk_shutdown |= RCV_SHUTDOWN;
- if (smc->clcsock && smc->clcsock->sk)
- smc->clcsock->sk->sk_shutdown |= RCV_SHUTDOWN;
- sock_set_flag(&smc->sk, SOCK_DONE);
-
+ lock_sock(&smc->sk);
old_state = sk->sk_state;

+ if (!conn->alert_token_local) {
+ /* abnormal termination */
+ smc_close_active_abort(smc);
+ goto wakeup;
+ }
+
+ rxflags = &smc->conn.local_rx_ctrl.conn_state_flags;
if (rxflags->peer_conn_abort) {
smc_close_passive_abort_received(smc);
goto wakeup;
@@ -373,11 +377,12 @@ void smc_close_passive_received(struct smc_sock *smc)
sk->sk_write_space(sk); /* wakeup blocked sndbuf producers */

if ((sk->sk_state == SMC_CLOSED) &&
- (sock_flag(sk, SOCK_DEAD) || (old_state == SMC_INIT))) {
+ (sock_flag(sk, SOCK_DEAD) || !sk->sk_socket)) {
smc_conn_free(&smc->conn);
schedule_delayed_work(&smc->sock_put_work,
SMC_CLOSE_SOCK_PUT_DELAY);
}
+ release_sock(&smc->sk);
}

void smc_close_sock_put_work(struct work_struct *work)
@@ -442,3 +447,9 @@ int smc_close_shutdown_write(struct smc_sock *smc)
sk->sk_state_change(&smc->sk);
return rc;
}
+
+/* Initialize close properties on connection establishment. */
+void smc_close_init(struct smc_sock *smc)
+{
+ INIT_WORK(&smc->conn.close_work, smc_close_passive_work);
+}
diff --git a/net/smc/smc_close.h b/net/smc/smc_close.h
index bc9a2df..4a3d99a 100644
--- a/net/smc/smc_close.h
+++ b/net/smc/smc_close.h
@@ -21,8 +21,8 @@
void smc_close_wake_tx_prepared(struct smc_sock *smc);
void smc_close_active_abort(struct smc_sock *smc);
int smc_close_active(struct smc_sock *smc);
-void smc_close_passive_received(struct smc_sock *smc);
void smc_close_sock_put_work(struct work_struct *work);
int smc_close_shutdown_write(struct smc_sock *smc);
+void smc_close_init(struct smc_sock *smc);

#endif /* SMC_CLOSE_H */
diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c
index 0eac633..65020e9 100644
--- a/net/smc/smc_core.c
+++ b/net/smc/smc_core.c
@@ -316,7 +316,7 @@ void smc_lgr_terminate(struct smc_link_group *lgr)
smc = container_of(conn, struct smc_sock, conn);
sock_hold(&smc->sk);
__smc_lgr_unregister_conn(conn);
- smc_close_active_abort(smc);
+ schedule_work(&conn->close_work);
sock_put(&smc->sk);
node = rb_first(&lgr->conns_all);
}
--
2.10.2