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

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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@hammerspace.com>
This commit is contained in:
Trond Myklebust 2019-01-30 14:51:26 -05:00
parent a1231fda7e
commit 0ffe86f480
1 changed files with 24 additions and 2 deletions
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26
net/sunrpc/xprtsock.c
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@ -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);
}