Commit 9a349219 authored by David S. Miller's avatar David S. Miller
Browse files

Merge branch 'AF_VSOCK-missed-wakeups' 

Claudio Imbrenda says:

====================
AF_VSOCK: Shrink the area influenced by prepare_to_wait

This patchset applies on net-next.

I think I found a problem with the patch submitted by Laura Abbott
( https://lkml.org/lkml/2016/2/4/711 ): we might miss wakeups.
Since the condition is not checked between the prepare_to_wait and the
schedule(), if a wakeup happens after the condition is checked but before
the sleep happens, and we miss it. ( A description of the problem can be
found here: http://www.makelinux.net/ldd3/chp-6-sect-2

 ).

The first patch reverts the previous broken patch, while the second patch
properly fixes the sleep-while-waiting issue.
====================

Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parents 9a0384c0 f7f9b5e7

net/vmw_vsock/af_vsock.c

+87 −68
Original line number Diff line number Diff line
@@ -1209,10 +1209,14 @@ static int vsock_stream_connect(struct socket *sock, struct sockaddr *addr, 


		if (signal_pending(current)) {

			err = sock_intr_errno(timeout);

			goto out_wait_error;

			sk->sk_state = SS_UNCONNECTED;

			sock->state = SS_UNCONNECTED;

			goto out_wait;

		} else if (timeout == 0) {

			err = -ETIMEDOUT;

			goto out_wait_error;

			sk->sk_state = SS_UNCONNECTED;

			sock->state = SS_UNCONNECTED;

			goto out_wait;

		}



		prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
@@ -1220,20 +1224,17 @@ static int vsock_stream_connect(struct socket *sock, struct sockaddr *addr, 


	if (sk->sk_err) {

		err = -sk->sk_err;

		goto out_wait_error;

	} else

		sk->sk_state = SS_UNCONNECTED;

		sock->state = SS_UNCONNECTED;

	} else {

		err = 0;

	}



out_wait:

	finish_wait(sk_sleep(sk), &wait);

out:

	release_sock(sk);

	return err;



out_wait_error:

	sk->sk_state = SS_UNCONNECTED;

	sock->state = SS_UNCONNECTED;

	goto out_wait;

}



static int vsock_accept(struct socket *sock, struct socket *newsock, int flags)
@@ -1270,18 +1271,20 @@ static int vsock_accept(struct socket *sock, struct socket *newsock, int flags) 
	       listener->sk_err == 0) {

		release_sock(listener);

		timeout = schedule_timeout(timeout);

		finish_wait(sk_sleep(listener), &wait);

		lock_sock(listener);



		if (signal_pending(current)) {

			err = sock_intr_errno(timeout);

			goto out_wait;

			goto out;

		} else if (timeout == 0) {

			err = -EAGAIN;

			goto out_wait;

			goto out;

		}



		prepare_to_wait(sk_sleep(listener), &wait, TASK_INTERRUPTIBLE);

	}

	finish_wait(sk_sleep(listener), &wait);



	if (listener->sk_err)

		err = -listener->sk_err;
@@ -1301,19 +1304,15 @@ static int vsock_accept(struct socket *sock, struct socket *newsock, int flags) 
		 */

		if (err) {

			vconnected->rejected = true;

			release_sock(connected);

			sock_put(connected);

			goto out_wait;

		}



		} else {

			newsock->state = SS_CONNECTED;

			sock_graft(connected, newsock);

		}



		release_sock(connected);

		sock_put(connected);

	}



out_wait:

	finish_wait(sk_sleep(listener), &wait);

out:

	release_sock(listener);

	return err;
@@ -1557,9 +1556,11 @@ static int vsock_stream_sendmsg(struct socket *sock, struct msghdr *msg, 
	if (err < 0)

		goto out;





	while (total_written < len) {

		ssize_t written;



		prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);

		while (vsock_stream_has_space(vsk) == 0 &&

		       sk->sk_err == 0 &&

		       !(sk->sk_shutdown & SEND_SHUTDOWN) &&
@@ -1568,27 +1569,33 @@ static int vsock_stream_sendmsg(struct socket *sock, struct msghdr *msg, 
			/* Don't wait for non-blocking sockets. */

			if (timeout == 0) {

				err = -EAGAIN;

				goto out_wait;

				finish_wait(sk_sleep(sk), &wait);

				goto out_err;

			}



			err = transport->notify_send_pre_block(vsk, &send_data);

			if (err < 0)

				goto out_wait;

			if (err < 0) {

				finish_wait(sk_sleep(sk), &wait);

				goto out_err;

			}



			release_sock(sk);

			prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);

			timeout = schedule_timeout(timeout);

			finish_wait(sk_sleep(sk), &wait);

			lock_sock(sk);

			if (signal_pending(current)) {

				err = sock_intr_errno(timeout);

				goto out_wait;

				finish_wait(sk_sleep(sk), &wait);

				goto out_err;

			} else if (timeout == 0) {

				err = -EAGAIN;

				goto out_wait;

				finish_wait(sk_sleep(sk), &wait);

				goto out_err;

			}



			prepare_to_wait(sk_sleep(sk), &wait,

					TASK_INTERRUPTIBLE);

		}

		finish_wait(sk_sleep(sk), &wait);



		/* These checks occur both as part of and after the loop

		 * conditional since we need to check before and after
@@ -1596,16 +1603,16 @@ static int vsock_stream_sendmsg(struct socket *sock, struct msghdr *msg, 
		 */

		if (sk->sk_err) {

			err = -sk->sk_err;

			goto out_wait;

			goto out_err;

		} else if ((sk->sk_shutdown & SEND_SHUTDOWN) ||

			   (vsk->peer_shutdown & RCV_SHUTDOWN)) {

			err = -EPIPE;

			goto out_wait;

			goto out_err;

		}



		err = transport->notify_send_pre_enqueue(vsk, &send_data);

		if (err < 0)

			goto out_wait;

			goto out_err;



		/* Note that enqueue will only write as many bytes as are free

		 * in the produce queue, so we don't need to ensure len is
@@ -1618,7 +1625,7 @@ static int vsock_stream_sendmsg(struct socket *sock, struct msghdr *msg, 
				len - total_written);

		if (written < 0) {

			err = -ENOMEM;

			goto out_wait;

			goto out_err;

		}



		total_written += written;
@@ -1626,11 +1633,11 @@ static int vsock_stream_sendmsg(struct socket *sock, struct msghdr *msg, 
		err = transport->notify_send_post_enqueue(

				vsk, written, &send_data);

		if (err < 0)

			goto out_wait;

			goto out_err;



	}



out_wait:

out_err:

	if (total_written > 0)

		err = total_written;

out:
@@ -1715,17 +1722,58 @@ vsock_stream_recvmsg(struct socket *sock, struct msghdr *msg, size_t len, 




	while (1) {

		s64 ready = vsock_stream_has_data(vsk);

		s64 ready;



		prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);

		ready = vsock_stream_has_data(vsk);



		if (ready == 0) {

			if (sk->sk_err != 0 ||

			    (sk->sk_shutdown & RCV_SHUTDOWN) ||

			    (vsk->peer_shutdown & SEND_SHUTDOWN)) {

				finish_wait(sk_sleep(sk), &wait);

				break;

			}

			/* Don't wait for non-blocking sockets. */

			if (timeout == 0) {

				err = -EAGAIN;

				finish_wait(sk_sleep(sk), &wait);

				break;

			}



			err = transport->notify_recv_pre_block(

					vsk, target, &recv_data);

			if (err < 0) {

				finish_wait(sk_sleep(sk), &wait);

				break;

			}

			release_sock(sk);

			timeout = schedule_timeout(timeout);

			lock_sock(sk);



			if (signal_pending(current)) {

				err = sock_intr_errno(timeout);

				finish_wait(sk_sleep(sk), &wait);

				break;

			} else if (timeout == 0) {

				err = -EAGAIN;

				finish_wait(sk_sleep(sk), &wait);

				break;

			}

		} else {

			ssize_t read;



			finish_wait(sk_sleep(sk), &wait);



			if (ready < 0) {

			/* Invalid queue pair content. XXX This should be

			 * changed to a connection reset in a later change.

				/* Invalid queue pair content. XXX This should

				* be changed to a connection reset in a later

				* change.

				*/



				err = -ENOMEM;

				goto out;

		} else if (ready > 0) {

			ssize_t read;

			}



			err = transport->notify_recv_pre_dequeue(

					vsk, target, &recv_data);
@@ -1752,35 +1800,6 @@ vsock_stream_recvmsg(struct socket *sock, struct msghdr *msg, size_t len, 
				break;



			target -= read;

		} else {

			if (sk->sk_err != 0 || (sk->sk_shutdown & RCV_SHUTDOWN)

			    || (vsk->peer_shutdown & SEND_SHUTDOWN)) {

				break;

			}

			/* Don't wait for non-blocking sockets. */

			if (timeout == 0) {

				err = -EAGAIN;

				break;

			}



			err = transport->notify_recv_pre_block(

					vsk, target, &recv_data);

			if (err < 0)

				break;



			release_sock(sk);

			prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);

			timeout = schedule_timeout(timeout);

			finish_wait(sk_sleep(sk), &wait);

			lock_sock(sk);



			if (signal_pending(current)) {

				err = sock_intr_errno(timeout);

				break;

			} else if (timeout == 0) {

				err = -EAGAIN;

				break;

			}

		}

	}

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