[dpdk-dev] i40e: Unchecked return value

  Calling i40e_switch_tx_queue without checking return value.
Fixed by add warning log information if return failed.

Fixes: 71d35259ff67 ("i40e: tear down flow director")
Coverity ID 13208

Signed-off-by: Slawomir Mrozowicz <slawomirx.mrozowicz@intel.com>
---
 drivers/net/i40e/i40e_fdir.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)
  

> -----Original Message-----
> From: Mrozowicz, SlawomirX
> Sent: Monday, May 23, 2016 8:25 PM
> To: Zhang, Helin <helin.zhang@intel.com>; Wu, Jingjing <jingjing.wu@intel.com>
> Cc: dev@dpdk.org; Mrozowicz, SlawomirX <slawomirx.mrozowicz@intel.com>
> Subject: [PATCH] i40e: Unchecked return value
> 
> Calling i40e_switch_tx_queue without checking return value.
> Fixed by add warning log information if return failed.
> 
> Fixes: 71d35259ff67 ("i40e: tear down flow director") Coverity ID 13208
> 
> Signed-off-by: Slawomir Mrozowicz <slawomirx.mrozowicz@intel.com>
Acked-by: Helin Zhang <helin.zhang@intel.com>
  

On Mon, May 23, 2016 at 02:25:15PM +0200, Slawomir Mrozowicz wrote:
> Calling i40e_switch_tx_queue without checking return value.
> Fixed by add warning log information if return failed.
> 
> Fixes: 71d35259ff67 ("i40e: tear down flow director")
> Coverity ID 13208
> 
> Signed-off-by: Slawomir Mrozowicz <slawomirx.mrozowicz@intel.com>
> ---
>  drivers/net/i40e/i40e_fdir.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/i40e/i40e_fdir.c b/drivers/net/i40e/i40e_fdir.c
> index 8aa41e5..d0bdf2c 100644
> --- a/drivers/net/i40e/i40e_fdir.c
> +++ b/drivers/net/i40e/i40e_fdir.c
> @@ -288,11 +288,14 @@ i40e_fdir_teardown(struct i40e_pf *pf)
>  {
>  	struct i40e_hw *hw = I40E_PF_TO_HW(pf);
>  	struct i40e_vsi *vsi;
> +	int err = I40E_SUCCESS;
>  
>  	vsi = pf->fdir.fdir_vsi;
>  	if (!vsi)
>  		return;
> -	i40e_switch_tx_queue(hw, vsi->base_queue, FALSE);
> +	err = i40e_switch_tx_queue(hw, vsi->base_queue, FALSE);
> +	if (err)
> +		PMD_DRV_LOG(WARNING, "Failed to do FDIR TX switch off.");
>  	i40e_switch_rx_queue(hw, vsi->base_queue, FALSE);

So, we have a failure when we can't swtich off flow director in a queue. How
serious is this? Is it something that can be completely ignored, or is printing
a warning sufficient? What, if anything, should the user do about the warning?

I'm just concerned that this patch doesn't seem to help the overall usability
of DPDK much. We print a warning, which will probably be of absolutely no use
to the user at all. It doesn't tell the user what the failure will mean in
practical terms - will the failure mean that transmit won't work, that packets
may be corrupted, may go out on a wrong queue, etc., or how the user can prevent
the error from happening in the future.

Please review patch to ensure this is the best way to fix this error - if any
fix is needed. If the error doesn't cause any problematic user effects, then
just mark the coverity issue as a false positive (or does it work casting the
function to (void) as it is called?). If the error does have problematic effects,
please provide useful information to the user.

/Bruce