Because we clear XPRT_SOCK_DATA_READY before reading, we can end up
with a situation where new data arrives, causing xs_data_ready() to
queue up a second receive worker job for the same socket, which then
immediately gets stuck waiting on the transport receive mutex.
The fix is to only clear XPRT_SOCK_DATA_READY once we're done reading,
and then to use poll() to check if we might need to queue up a new
job in order to deal with any new data.
Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
---
net/sunrpc/xprtsock.c | 17 +++++++++++++++--
1 file changed, 15 insertions(+), 2 deletions(-)
diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index f5d7dcd9e8d9..a721c843d5d3 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -656,13 +656,25 @@ xs_read_stream(struct sock_xprt *transport, int flags)
return ret != 0 ? ret : -ESHUTDOWN;
}
+static void xs_poll_check_readable(struct sock_xprt *transport)
+{
+ struct socket *sock = transport->sock;
+ __poll_t events;
+
+ clear_bit(XPRT_SOCK_DATA_READY, &transport->sock_state);
+ events = sock->ops->poll(NULL, sock, NULL);
+ if (!(events & (EPOLLIN | EPOLLRDNORM)) || events & EPOLLRDHUP)
+ return;
+ if (!test_and_set_bit(XPRT_SOCK_DATA_READY, &transport->sock_state))
+ queue_work(xprtiod_workqueue, &transport->recv_worker);
+}
+
static void xs_stream_data_receive(struct sock_xprt *transport)
{
size_t read = 0;
ssize_t ret = 0;
mutex_lock(&transport->recv_mutex);
- clear_bit(XPRT_SOCK_DATA_READY, &transport->sock_state);
if (transport->sock == NULL)
goto out;
for (;;) {
@@ -672,6 +684,7 @@ static void xs_stream_data_receive(struct sock_xprt *transport)
read += ret;
cond_resched();
}
+ xs_poll_check_readable(transport);
out:
mutex_unlock(&transport->recv_mutex);
trace_xs_stream_read_data(&transport->xprt, ret, read);
@@ -1362,7 +1375,6 @@ static void xs_udp_data_receive(struct sock_xprt *transport)
int err;
mutex_lock(&transport->recv_mutex);
- clear_bit(XPRT_SOCK_DATA_READY, &transport->sock_state);
sk = transport->inet;
if (sk == NULL)
goto out;
@@ -1374,6 +1386,7 @@ static void xs_udp_data_receive(struct sock_xprt *transport)
consume_skb(skb);
cond_resched();
}
+ xs_poll_check_readable(transport);
out:
mutex_unlock(&transport->recv_mutex);
}
--
2.20.1
