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Commit 0ffe86f4 authored by Trond Myklebust's avatar Trond Myklebust
Browse files

SUNRPC: Use poll() to fix up the socket requeue races 



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: default avatarTrond Myklebust <trond.myklebust@hammerspace.com>
parent a1231fda

net/sunrpc/xprtsock.c

+24 −2
Original line number Diff line number Diff line
@@ -656,13 +656,34 @@ xs_read_stream(struct sock_xprt *transport, int flags) 
	return ret != 0 ? ret : -ESHUTDOWN;

}



static __poll_t xs_poll_socket(struct sock_xprt *transport)

{

	return transport->sock->ops->poll(NULL, transport->sock, NULL);

}



static bool xs_poll_socket_readable(struct sock_xprt *transport)

{

	__poll_t events = xs_poll_socket(transport);



	return (events & (EPOLLIN | EPOLLRDNORM)) && !(events & EPOLLRDHUP);

}



static void xs_poll_check_readable(struct sock_xprt *transport)

{



	clear_bit(XPRT_SOCK_DATA_READY, &transport->sock_state);

	if (!xs_poll_socket_readable(transport))

		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 +693,7 @@ 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 +1384,6 @@ 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 +1395,7 @@ 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);

}