On Tue, 2024-04-23 at 06:57 +0300, Daniel Jurgens wrote:
> Once the RTNL locking around the control buffer is removed there can be
> contention on the per queue RX interrupt coalescing data. Use a mutex
> per queue. A mutex is required because virtnet_send_command can sleep.
> 
> Signed-off-by: Daniel Jurgens <dani...@nvidia.com>
> ---
>  drivers/net/virtio_net.c | 53 +++++++++++++++++++++++++++++++---------
>  1 file changed, 41 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index af9048ddc3c1..033e1d6ea31b 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -184,6 +184,9 @@ struct receive_queue {
>       /* Is dynamic interrupt moderation enabled? */
>       bool dim_enabled;
>  
> +     /* Used to protect dim_enabled and inter_coal */
> +     struct mutex dim_lock;
> +
>       /* Dynamic Interrupt Moderation */
>       struct dim dim;
>  
> @@ -2218,6 +2221,10 @@ static int virtnet_poll(struct napi_struct *napi, int 
> budget)
>       /* Out of packets? */
>       if (received < budget) {
>               napi_complete = virtqueue_napi_complete(napi, rq->vq, received);
> +             /* Intentionally not taking dim_lock here. This could result
> +              * in a net_dim call with dim now disabled. But 
> virtnet_rx_dim_work
> +              * will take the lock not update settings if dim is now 
> disabled.

Minor nit: the above comment looks confusing/mangled to me ?!?

                   will take the lock and will not update settings...

Thanks,

Paolo


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