Re: [RFC PATCH v5 02/19] af_vsock: separate wait data loop

[Arseny Krasnov]

On 25.02.2021 17:24, Jorgen Hansen wrote:
>> On 18 Feb 2021, at 06:36, Arseny Krasnov <arseny.krasnov@xxxxxxxxxxxxx> wrote:
>>
>> This moves wait loop for data to dedicated function, because later
>> it will be used by SEQPACKET data receive loop.
>>
>> Signed-off-by: Arseny Krasnov <arseny.krasnov@xxxxxxxxxxxxx>
>> ---
>> net/vmw_vsock/af_vsock.c | 155 +++++++++++++++++++++------------------
>> 1 file changed, 83 insertions(+), 72 deletions(-)
>>
>> diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>> index 656370e11707..6cf7bb977aa1 100644
>> --- a/net/vmw_vsock/af_vsock.c
>> +++ b/net/vmw_vsock/af_vsock.c
>> @@ -1832,6 +1832,68 @@ static int vsock_connectible_sendmsg(struct socket *sock, struct msghdr *msg,
>> 	return err;
>> }
>>
>> +static int vsock_wait_data(struct sock *sk, struct wait_queue_entry *wait,
>> +			   long timeout,
>> +			   struct vsock_transport_recv_notify_data *recv_data,
>> +			   size_t target)
>> +{
>> +	const struct vsock_transport *transport;
>> +	struct vsock_sock *vsk;
>> +	s64 data;
>> +	int err;
>> +
>> +	vsk = vsock_sk(sk);
>> +	err = 0;
>> +	transport = vsk->transport;
>> +	prepare_to_wait(sk_sleep(sk), wait, TASK_INTERRUPTIBLE);
>> +
>> +	while ((data = vsock_stream_has_data(vsk)) == 0) {
> In the original code, the prepare_to_wait() is called for each iteration of the while loop. In this
> version, it is only called once. So if we do multiple iterations, the thread would be in the
> TASK_RUNNING state, and subsequent schedule_timeout() will return immediately. So
> looks like the prepare_to_wait() should be move here, in case we have a spurious wake_up.
Thank you, i'll fix it
>
>> +		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;
>> +		}
>> +
>> +		if (recv_data) {
>> +			err = transport->notify_recv_pre_block(vsk, target, recv_data);
>> +			if (err < 0)
>> +				break;
>> +		}
>> +
>> +		release_sock(sk);
>> +		timeout = schedule_timeout(timeout);
>> +		lock_sock(sk);
>> +
>> +		if (signal_pending(current)) {
>> +			err = sock_intr_errno(timeout);
>> +			break;
>> +		} else if (timeout == 0) {
>> +			err = -EAGAIN;
>> +			break;
>> +		}
>> +	}
>> +
>> +	finish_wait(sk_sleep(sk), wait);
>> +
>> +	if (err)
>> +		return err;
>> +
>> +	/* Internal transport error when checking for available
>> +	 * data. XXX This should be changed to a connection
>> +	 * reset in a later change.
>> +	 */
>> +	if (data < 0)
>> +		return -ENOMEM;
>> +
>> +	return data;
>> +}
>> +
>> static int
>> vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
>> 			  int flags)
>> @@ -1911,85 +1973,34 @@ vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
>>
>>
>> 	while (1) {
>> -		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;
>> -			}
>> +		ssize_t read;
>>
>> -			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);
>> +		err = vsock_wait_data(sk, &wait, timeout, &recv_data, target);
>> +		if (err <= 0)
>> +			break;
>>
>> -			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.
>> -				*/
>> -
>> -				err = -ENOMEM;
>> -				goto out;
>> -			}
>> -
>> -			err = transport->notify_recv_pre_dequeue(
>> -					vsk, target, &recv_data);
>> -			if (err < 0)
>> -				break;
>> +		err = transport->notify_recv_pre_dequeue(vsk, target,
>> +							 &recv_data);
>> +		if (err < 0)
>> +			break;
>>
>> -			read = transport->stream_dequeue(
>> -					vsk, msg,
>> -					len - copied, flags);
>> -			if (read < 0) {
>> -				err = -ENOMEM;
>> -				break;
>> -			}
>> +		read = transport->stream_dequeue(vsk, msg, len - copied, flags);
>> +		if (read < 0) {
>> +			err = -ENOMEM;
>> +			break;
>> +		}
>>
>> -			copied += read;
>> +		copied += read;
>>
>> -			err = transport->notify_recv_post_dequeue(
>> -					vsk, target, read,
>> -					!(flags & MSG_PEEK), &recv_data);
>> -			if (err < 0)
>> -				goto out;
>> +		err = transport->notify_recv_post_dequeue(vsk, target, read,
>> +						!(flags & MSG_PEEK), &recv_data);
>> +		if (err < 0)
>> +			goto out;
>>
>> -			if (read >= target || flags & MSG_PEEK)
>> -				break;
>> +		if (read >= target || flags & MSG_PEEK)
>> +			break;
>>
>> -			target -= read;
>> -		}
>> +		target -= read;
>> 	}
>>
>> 	if (sk->sk_err)
>> -- 
>> 2.25.1
>>
>