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SubjectRe: [PATCH v4 3/5] vsock/virtio: fix locking in virtio_transport_inc_tx_pkt()
On Wed, Jul 17, 2019 at 01:30:28PM +0200, Stefano Garzarella wrote:
> fwd_cnt and last_fwd_cnt are protected by rx_lock, so we should use
> the same spinlock also if we are in the TX path.
>
> Move also buf_alloc under the same lock.
>
> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>

Wait a second is this a bugfix?
If it's used under the wrong lock won't values get corrupted?
Won't traffic then stall or more data get to sent than
credits?

> ---
> include/linux/virtio_vsock.h | 2 +-
> net/vmw_vsock/virtio_transport_common.c | 4 ++--
> 2 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
> index 49fc9d20bc43..4c7781f4b29b 100644
> --- a/include/linux/virtio_vsock.h
> +++ b/include/linux/virtio_vsock.h
> @@ -35,7 +35,6 @@ struct virtio_vsock_sock {
>
> /* Protected by tx_lock */
> u32 tx_cnt;
> - u32 buf_alloc;
> u32 peer_fwd_cnt;
> u32 peer_buf_alloc;
>
> @@ -43,6 +42,7 @@ struct virtio_vsock_sock {
> u32 fwd_cnt;
> u32 last_fwd_cnt;
> u32 rx_bytes;
> + u32 buf_alloc;
> struct list_head rx_queue;
> };
>
> diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
> index a85559d4d974..34a2b42313b7 100644
> --- a/net/vmw_vsock/virtio_transport_common.c
> +++ b/net/vmw_vsock/virtio_transport_common.c
> @@ -210,11 +210,11 @@ static void virtio_transport_dec_rx_pkt(struct virtio_vsock_sock *vvs,
>
> void virtio_transport_inc_tx_pkt(struct virtio_vsock_sock *vvs, struct virtio_vsock_pkt *pkt)
> {
> - spin_lock_bh(&vvs->tx_lock);
> + spin_lock_bh(&vvs->rx_lock);
> vvs->last_fwd_cnt = vvs->fwd_cnt;
> pkt->hdr.fwd_cnt = cpu_to_le32(vvs->fwd_cnt);
> pkt->hdr.buf_alloc = cpu_to_le32(vvs->buf_alloc);
> - spin_unlock_bh(&vvs->tx_lock);
> + spin_unlock_bh(&vvs->rx_lock);
> }
> EXPORT_SYMBOL_GPL(virtio_transport_inc_tx_pkt);
>
> --
> 2.20.1

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