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

Arseny Krasnov
2021-02-25T17:04:00Z

On 25.02.2021 17:24, Jorgen Hansen wrote:
>> On 18 Feb 2021, at 06:36, Arseny Krasnov <arseny.krasnov@kaspersky.com> 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@kaspersky.com>
>> ---
>> 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
>>
>