From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yongseok Koh Subject: Re: [PATCH] net/mlx5: handle expected errno properly Date: Tue, 28 Aug 2018 13:42:18 -0700 Message-ID: <20180828204217.GA45628@yongseok-MBP.local> References: <20180823063851.32559-1-jackmin@mellanox.com> <20180823210808.GA31847@yongseok-MBP.local> <20180824064500.uopotkliiaygvvny@MTBC-JACKMIN.mtl.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii To: Shahaf Shuler , dev@dpdk.org, xuemingl@mellanox.com Return-path: Received: from EUR01-HE1-obe.outbound.protection.outlook.com (mail-he1eur01on0050.outbound.protection.outlook.com [104.47.0.50]) by dpdk.org (Postfix) with ESMTP id AB24C2BB1 for ; Tue, 28 Aug 2018 22:42:12 +0200 (CEST) Content-Disposition: inline In-Reply-To: <20180824064500.uopotkliiaygvvny@MTBC-JACKMIN.mtl.com> List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On Fri, Aug 24, 2018 at 02:45:00PM +0800, Jack MIN wrote: > On Thu, Aug 23, 2018 at 02:08:09PM -0700, Yongseok Koh wrote: > > On Thu, Aug 23, 2018 at 02:38:51PM +0800, Xiaoyu Min wrote: > > > rte_errno is a per thread variable and is widely used as an > > > error indicator, which means a function could affect > > > other functions' results by setting rte_errno carelessly > > > > > > During rxq setup, an EINVAL rte_errno is expected since > > > the queues are not created yet > > > So rte_errno is cleared when it is EINVAL as expected > > > > > > Signed-off-by: Xiaoyu Min > > > --- > > > drivers/net/mlx5/mlx5_rxq.c | 20 +++++++++++++++----- > > > 1 file changed, 15 insertions(+), 5 deletions(-) > > > > > > diff --git a/drivers/net/mlx5/mlx5_rxq.c b/drivers/net/mlx5/mlx5_rxq.c > > > index 1f7bfd4..e7056e8 100644 > > > --- a/drivers/net/mlx5/mlx5_rxq.c > > > +++ b/drivers/net/mlx5/mlx5_rxq.c > > > @@ -443,6 +443,7 @@ > > > struct mlx5_rxq_data *rxq = (*priv->rxqs)[idx]; > > > struct mlx5_rxq_ctrl *rxq_ctrl = > > > container_of(rxq, struct mlx5_rxq_ctrl, rxq); > > > + int ret = 0; > > > > > > if (!rte_is_power_of_2(desc)) { > > > desc = 1 << log2above(desc); > > > @@ -459,13 +460,21 @@ > > > rte_errno = EOVERFLOW; > > > return -rte_errno; > > > } > > > - if (!mlx5_rxq_releasable(dev, idx)) { > > > + ret = mlx5_rxq_releasable(dev, idx); > > > + if (!ret) { > > > DRV_LOG(ERR, "port %u unable to release queue index %u", > > > dev->data->port_id, idx); > > > rte_errno = EBUSY; > > > return -rte_errno; > > > + } else if (ret == -EINVAL) { > > > + /** > > > + * on the first time, rx queue doesn't exist, > > > + * so just ignore this error and reset rte_errno. > > > + */ > > > + rte_errno = 0; > > > > Unless this function returns failure, the rte_errno will be ignored by caller > > and caller shouldn't assume rte_errno has 0. Caller will assume it is garbage > > data in case of success. So we can silently ignore this case. Does it cause any > > issue in application side? > > > Not application side but mlx5 PMD this time: > **mlx5_fdir_filter_delete** > which just _return -rte_errno;_ Looks like an error. mlx5_fdir_filter_delete() can't be like that. We seem to have lost the code while refactoring it. Let take it offline. > For sure, _mlx5_fdir_filter_delete_ should be more defensive, should not assume > rte_errno is zero if no error happened. > However if the caller know that an error will happen and rte_errno will become > meaningless (garbage) for the succeeding functions, Catching the expected error > and resetting rte_errno will be better. What do you think? Still don't understand clearly. There would be many other similar cases where we don't clear rte_errno when returning success. I don't understand why this case should be taken as a special one?? Thanks Yongseok