From 0ffe86f48026b7f34db22d1004bc9992f0db8b33 Mon Sep 17 00:00:00 2001 From: Trond Myklebust Date: Wed, 30 Jan 2019 14:51:26 -0500 Subject: [PATCH] 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: Trond Myklebust --- net/sunrpc/xprtsock.c | 26 ++++++++++++++++++++++++-- 1 file changed, 24 insertions(+), 2 deletions(-) diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c index f5d7dcd9e8d9..da45bb1e931e 100644 --- a/net/sunrpc/xprtsock.c +++ b/net/sunrpc/xprtsock.c @@ -656,13 +656,34 @@ out_err: 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); }