On Thu, Mar 21, 2024 at 7:46 PM Heng Qi <hengqi@xxxxxxxxxxxxxxxxx> wrote:
>
> When the dim worker is scheduled, if it fails to acquire the lock,
> dim may not be able to return to the working state later.
>
> For example, the following single queue scenario:
> 1. The dim worker of rxq0 is scheduled, and the dim status is
> changed to DIM_APPLY_NEW_PROFILE;
> 2. The ethtool command is holding rtnl lock;
> 3. Since the rtnl lock is already held, virtnet_rx_dim_work fails
> to acquire the lock and exits;
>
> Then, even if net_dim is invoked again, it cannot work because the
> state is not restored to DIM_START_MEASURE.
>
> Fixes: 6208799553a8 ("virtio-net: support rx netdim")
> Signed-off-by: Heng Qi <hengqi@xxxxxxxxxxxxxxxxx>
> ---
> drivers/net/virtio_net.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index c22d111..0ebe322 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -3563,8 +3563,10 @@ static void virtnet_rx_dim_work(struct work_struct *work)
> struct dim_cq_moder update_moder;
> int i, qnum, err;
>
> - if (!rtnl_trylock())
> + if (!rtnl_trylock()) {
> + schedule_work(&dim->work);
> return;
> + }
Patch looks fine but I wonder if a delayed schedule is better.
Thanks
>
> /* Each rxq's work is queued by "net_dim()->schedule_work()"
> * in response to NAPI traffic changes. Note that dim->profile_ix
> --
> 1.8.3.1
>
