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rds: use RCU to synchronize work-enqueue with connection teardown 

rds_sendmsg() can enqueue work on cp_send_w from process context, but
it should not enqueue this work if connection teardown  has commenced
(else we risk enquing work after rds_conn_path_destroy() has assumed that
all work has been cancelled/flushed).

Similarly some other functions like rds_cong_queue_updates
and rds_tcp_data_ready are called in softirq context, and may end
up enqueuing work on rds_wq after rds_conn_path_destroy() has assumed
that all workqs are quiesced.

Check the RDS_DESTROY_PENDING bit and use rcu synchronization to avoid
all these races.

Signed-off-by: Sowmini Varadhan <sowmini.varadhan@oracle.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Sowmini Varadhan 2018-01-04 06:53:00 -08:00 committed by David S. Miller
parent c90ecbfaf5
commit 3db6e0d172
6 changed files with 81 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
net/rds/cong.c
View File

@ -219,7 +219,11 @@ void rds_cong_queue_updates(struct rds_cong_map *map)
spin_lock_irqsave(&rds_cong_lock, flags);
list_for_each_entry(conn, &map->m_conn_list, c_map_item) {
if (!test_and_set_bit(0, &conn->c_map_queued)) {
struct rds_conn_path *cp = &conn->c_path[0];
rcu_read_lock();
if (!test_and_set_bit(0, &conn->c_map_queued) &&
!test_bit(RDS_DESTROY_PENDING, &cp->cp_flags)) {
rds_stats_inc(s_cong_update_queued);
/* We cannot inline the call to rds_send_xmit() here
* for two reasons (both pertaining to a TCP transport):
@ -235,9 +239,9 @@ void rds_cong_queue_updates(struct rds_cong_map *map)
* therefore trigger warnings.
* Defer the xmit to rds_send_worker() instead.
*/
queue_delayed_work(rds_wq,
&conn->c_path[0].cp_send_w, 0);
queue_delayed_work(rds_wq, &cp->cp_send_w, 0);
}
rcu_read_unlock();
}
spin_unlock_irqrestore(&rds_cong_lock, flags);

21
net/rds/connection.c
View File

@ -366,8 +366,6 @@ void rds_conn_shutdown(struct rds_conn_path *cp)
* to the conn hash, so we never trigger a reconnect on this
* conn - the reconnect is always triggered by the active peer. */
cancel_delayed_work_sync(&cp->cp_conn_w);
if (test_bit(RDS_DESTROY_PENDING, &cp->cp_flags))
return;
rcu_read_lock();
if (!hlist_unhashed(&conn->c_hash_node)) {
rcu_read_unlock();
@ -390,6 +388,7 @@ static void rds_conn_path_destroy(struct rds_conn_path *cp)
return;
/* make sure lingering queued work won't try to ref the conn */
synchronize_rcu();
cancel_delayed_work_sync(&cp->cp_send_w);
cancel_delayed_work_sync(&cp->cp_recv_w);
@ -407,6 +406,11 @@ static void rds_conn_path_destroy(struct rds_conn_path *cp)
if (cp->cp_xmit_rm)
rds_message_put(cp->cp_xmit_rm);
WARN_ON(delayed_work_pending(&cp->cp_send_w));
WARN_ON(delayed_work_pending(&cp->cp_recv_w));
WARN_ON(delayed_work_pending(&cp->cp_conn_w));
WARN_ON(work_pending(&cp->cp_down_w));
cp->cp_conn->c_trans->conn_free(cp->cp_transport_data);
}
@ -686,10 +690,13 @@ void rds_conn_path_drop(struct rds_conn_path *cp, bool destroy)
{
atomic_set(&cp->cp_state, RDS_CONN_ERROR);
if (!destroy && test_bit(RDS_DESTROY_PENDING, &cp->cp_flags))
rcu_read_lock();
if (!destroy && test_bit(RDS_DESTROY_PENDING, &cp->cp_flags)) {
rcu_read_unlock();
return;
}
queue_work(rds_wq, &cp->cp_down_w);
rcu_read_unlock();
}
EXPORT_SYMBOL_GPL(rds_conn_path_drop);
@ -706,9 +713,15 @@ EXPORT_SYMBOL_GPL(rds_conn_drop);
*/
void rds_conn_path_connect_if_down(struct rds_conn_path *cp)
{
rcu_read_lock();
if (test_bit(RDS_DESTROY_PENDING, &cp->cp_flags)) {
rcu_read_unlock();
return;
}
if (rds_conn_path_state(cp) == RDS_CONN_DOWN &&
!test_and_set_bit(RDS_RECONNECT_PENDING, &cp->cp_flags))
queue_delayed_work(rds_wq, &cp->cp_conn_w, 0);
rcu_read_unlock();
}
EXPORT_SYMBOL_GPL(rds_conn_path_connect_if_down);

37
net/rds/send.c
View File

@ -162,6 +162,12 @@ restart:
goto out;
}
if (test_bit(RDS_DESTROY_PENDING, &cp->cp_flags)) {
release_in_xmit(cp);
ret = -ENETUNREACH; /* dont requeue send work */
goto out;
}
/*
* we record the send generation after doing the xmit acquire.
* if someone else manages to jump in and do some work, we'll use
@ -437,7 +443,12 @@ over_batch:
!list_empty(&cp->cp_send_queue)) && !raced) {
if (batch_count < send_batch_count)
goto restart;
queue_delayed_work(rds_wq, &cp->cp_send_w, 1);
rcu_read_lock();
if (test_bit(RDS_DESTROY_PENDING, &cp->cp_flags))
ret = -ENETUNREACH;
else
queue_delayed_work(rds_wq, &cp->cp_send_w, 1);
rcu_read_unlock();
} else if (raced) {
rds_stats_inc(s_send_lock_queue_raced);
}
@ -1151,6 +1162,11 @@ int rds_sendmsg(struct socket *sock, struct msghdr *msg, size_t payload_len)
else
cpath = &conn->c_path[0];
if (test_bit(RDS_DESTROY_PENDING, &cpath->cp_flags)) {
ret = -EAGAIN;
goto out;
}
rds_conn_path_connect_if_down(cpath);
ret = rds_cong_wait(conn->c_fcong, dport, nonblock, rs);
@ -1190,9 +1206,17 @@ int rds_sendmsg(struct socket *sock, struct msghdr *msg, size_t payload_len)
rds_stats_inc(s_send_queued);
ret = rds_send_xmit(cpath);
if (ret == -ENOMEM || ret == -EAGAIN)
queue_delayed_work(rds_wq, &cpath->cp_send_w, 1);
if (ret == -ENOMEM || ret == -EAGAIN) {
ret = 0;
rcu_read_lock();
if (test_bit(RDS_DESTROY_PENDING, &cpath->cp_flags))
ret = -ENETUNREACH;
else
queue_delayed_work(rds_wq, &cpath->cp_send_w, 1);
rcu_read_unlock();
}
if (ret)
goto out;
rds_message_put(rm);
return payload_len;
@ -1270,7 +1294,10 @@ rds_send_probe(struct rds_conn_path *cp, __be16 sport,
rds_stats_inc(s_send_pong);
/* schedule the send work on rds_wq */
queue_delayed_work(rds_wq, &cp->cp_send_w, 1);
rcu_read_lock();
if (!test_bit(RDS_DESTROY_PENDING, &cp->cp_flags))
queue_delayed_work(rds_wq, &cp->cp_send_w, 1);
rcu_read_unlock();
rds_message_put(rm);
return 0;

8
net/rds/tcp_recv.c
View File

@ -321,8 +321,12 @@ void rds_tcp_data_ready(struct sock *sk)
ready = tc->t_orig_data_ready;
rds_tcp_stats_inc(s_tcp_data_ready_calls);
if (rds_tcp_read_sock(cp, GFP_ATOMIC) == -ENOMEM)
queue_delayed_work(rds_wq, &cp->cp_recv_w, 0);
if (rds_tcp_read_sock(cp, GFP_ATOMIC) == -ENOMEM) {
rcu_read_lock();
if (!test_bit(RDS_DESTROY_PENDING, &cp->cp_flags))
queue_delayed_work(rds_wq, &cp->cp_recv_w, 0);
rcu_read_unlock();
}
out:
read_unlock_bh(&sk->sk_callback_lock);
ready(sk);

5
net/rds/tcp_send.c
View File

@ -202,8 +202,11 @@ void rds_tcp_write_space(struct sock *sk)
tc->t_last_seen_una = rds_tcp_snd_una(tc);
rds_send_path_drop_acked(cp, rds_tcp_snd_una(tc), rds_tcp_is_acked);
if ((refcount_read(&sk->sk_wmem_alloc) << 1) <= sk->sk_sndbuf)
rcu_read_lock();
if ((refcount_read(&sk->sk_wmem_alloc) << 1) <= sk->sk_sndbuf &&
!test_bit(RDS_DESTROY_PENDING, &cp->cp_flags))
queue_delayed_work(rds_wq, &cp->cp_send_w, 0);
rcu_read_unlock();
out:
read_unlock_bh(&sk->sk_callback_lock);

20
net/rds/threads.c
View File

@ -87,8 +87,12 @@ void rds_connect_path_complete(struct rds_conn_path *cp, int curr)
cp->cp_reconnect_jiffies = 0;
set_bit(0, &cp->cp_conn->c_map_queued);
queue_delayed_work(rds_wq, &cp->cp_send_w, 0);
queue_delayed_work(rds_wq, &cp->cp_recv_w, 0);
rcu_read_lock();
if (!test_bit(RDS_DESTROY_PENDING, &cp->cp_flags)) {
queue_delayed_work(rds_wq, &cp->cp_send_w, 0);
queue_delayed_work(rds_wq, &cp->cp_recv_w, 0);
}
rcu_read_unlock();
}
EXPORT_SYMBOL_GPL(rds_connect_path_complete);
@ -133,7 +137,10 @@ void rds_queue_reconnect(struct rds_conn_path *cp)
set_bit(RDS_RECONNECT_PENDING, &cp->cp_flags);
if (cp->cp_reconnect_jiffies == 0) {
cp->cp_reconnect_jiffies = rds_sysctl_reconnect_min_jiffies;
queue_delayed_work(rds_wq, &cp->cp_conn_w, 0);
rcu_read_lock();
if (!test_bit(RDS_DESTROY_PENDING, &cp->cp_flags))
queue_delayed_work(rds_wq, &cp->cp_conn_w, 0);
rcu_read_unlock();
return;
}
@ -141,8 +148,11 @@ void rds_queue_reconnect(struct rds_conn_path *cp)
rdsdebug("%lu delay %lu ceil conn %p for %pI4 -> %pI4\n",
rand % cp->cp_reconnect_jiffies, cp->cp_reconnect_jiffies,
conn, &conn->c_laddr, &conn->c_faddr);
queue_delayed_work(rds_wq, &cp->cp_conn_w,
rand % cp->cp_reconnect_jiffies);
rcu_read_lock();
if (!test_bit(RDS_DESTROY_PENDING, &cp->cp_flags))
queue_delayed_work(rds_wq, &cp->cp_conn_w,
rand % cp->cp_reconnect_jiffies);
rcu_read_unlock();
cp->cp_reconnect_jiffies = min(cp->cp_reconnect_jiffies * 2,
rds_sysctl_reconnect_max_jiffies);