Re: [PATCH 2/3] media: staging: rkisp1: params: don't release lock in isr before buffer is done

[Helen Koike <helen.koike@xxxxxxxxxxxxx>]

Hi Dafna,

Thanks for the patch

On 6/25/20 2:42 PM, Dafna Hirschfeld wrote:
> In the irq handler 'rkisp1_params_isr', the lock 'config_lock'
> should be held as long as the current buffer is used. Otherwise the
> stop_streaming calback might remove it from the list and
> pass it to userspace while it is referenced in the irq handler.
> 
> Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld@xxxxxxxxxxxxx>

I think we need to clarify what 'config_lock' protects, it seems it protects
the is_streaming variable and the buffer list.
I see it being used by rkisp1_params_config_parameter(), which doesn't look right to me.

> ---
>  drivers/staging/media/rkisp1/rkisp1-params.c | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/staging/media/rkisp1/rkisp1-params.c b/drivers/staging/media/rkisp1/rkisp1-params.c
> index 762c2259b807..bf006dbeee2d 100644
> --- a/drivers/staging/media/rkisp1/rkisp1-params.c
> +++ b/drivers/staging/media/rkisp1/rkisp1-params.c
> @@ -1210,10 +1210,11 @@ void rkisp1_params_isr(struct rkisp1_device *rkisp1, u32 isp_mis)
>  	if (!list_empty(&params->params))
>  		cur_buf = list_first_entry(&params->params,
>  					   struct rkisp1_buffer, queue);
> -	spin_unlock(&params->config_lock);
>  
> -	if (!cur_buf)
> +	if (!cur_buf) {
> +		spin_unlock(&params->config_lock);
>  		return;
> +	}
>  
>  	new_params = (struct rkisp1_params_cfg *)(cur_buf->vaddr[0]);
>  
> @@ -1228,13 +1229,11 @@ void rkisp1_params_isr(struct rkisp1_device *rkisp1, u32 isp_mis)
>  		isp_ctrl |= RKISP1_CIF_ISP_CTRL_ISP_CFG_UPD;
>  		rkisp1_write(params->rkisp1, isp_ctrl, RKISP1_CIF_ISP_CTRL);
>  
> -		spin_lock(&params->config_lock);
>  		list_del(&cur_buf->queue);
> -		spin_unlock(&params->config_lock);
> -
>  		cur_buf->vb.sequence = frame_sequence;
>  		vb2_buffer_done(&cur_buf->vb.vb2_buf, VB2_BUF_STATE_DONE);
>  	}

Maybe we could refactor this whole function, as mentioned by Robin in patch 3/3, we could remove
this identation with:

if (!(isp_mis & RKISP1_CIF_ISP_FRAME))
    return;

Keep in mind that params and stats were barely touched from the original driver, so don't be afraid to refactor things :)

Thanks
Helen


> +	spin_unlock(&params->config_lock);
>  }
>  
>  static const struct rkisp1_cif_isp_awb_meas_config rkisp1_awb_params_default_config = {
>