[dpdk-dev] [PATCH v5] net/virtio: fix wrong variable assignment in helper macro

[Maxime Coquelin]

On 9/18/20 11:55 AM, Vipul Ashri wrote:
> Inside Macro ASSIGN_UNLESS_EQUAL(var, val), assignment to var is always
> failing as assignment done using var_ having local scope only.
> This leads to TX packets not going out and found broken due to cleanup
> malfunctioning. This patch fixes the wrong variable assignment.
> 
> Fixes: 57f90f894588 ("net/virtio: reuse packed ring functions")
> Cc: stable at dpdk.org
> 
> Signed-off-by: Vipul Ashri <vipul.ashri at oracle.com>
> ---
>  drivers/net/virtio/virtqueue.h | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/virtio/virtqueue.h b/drivers/net/virtio/virtqueue.h
> index 105a9c00c..6ed50648c 100644
> --- a/drivers/net/virtio/virtqueue.h
> +++ b/drivers/net/virtio/virtqueue.h
> @@ -607,10 +607,10 @@ virtqueue_notify(struct virtqueue *vq)
>  
>  /* avoid write operation when necessary, to lessen cache issues */
>  #define ASSIGN_UNLESS_EQUAL(var, val) do {	\
> -	typeof(var) var_ = (var);		\
> -	typeof(val) val_ = (val);		\
> -	if ((var_) != (val_))			\
> -		(var_) = (val_);		\
> +	typeof(var) *const var_ = &(var);	\
> +	typeof(val)  const val_ = (val);	\
> +	if (*var_ != val_)			\
> +		*var_ = val_;			\
>  } while (0)
>  
>  #define virtqueue_clear_net_hdr(hdr) do {		\
> 

Reviewed-by: Maxime Coquelin <maxime.coquelin at redhat.com>

Thanks,
Maxime