On 06/05/20 14:43 +0100, Ferruh Yigit wrote:
> On 5/6/2020 1:33 PM, Gaëtan Rivet wrote:
> > On 06/05/20 12:48 +0100, Ferruh Yigit wrote:
> >> On 5/5/2020 8:10 PM, Gaetan Rivet wrote:
> >>> When a net_ring device is allocated, its device pointer is not set
> >>> before calling rte_eth_dev_probing_finish, which is incorrect.
> >>>
> >>> The following:
> >>> commit: 96cb19521147 ("net/ring: use EAL APIs in PMD specific API")
> >>> commit: a6992e961050 ("net/ring: set ethernet device field")
> >>>
> >>> already attempted to fix this issue in 17.08, which was fine at the
> >>> time. Adding the hook rte_eth_dev_probing_finish() however created this
> >>> bug, as the eth_dev exposed when this hook is executed is expected to be
> >>> complete.
> >>>
> >>> Remove the prior attempts to fix the issue in rte_pmd_ring_probe() and
> >>> write the pointer properly in do_eth_dev_ring_create().
> >>>
> >>> Cc: sta...@dpdk.org
> >>> Fixes: fbe90cdd776c ("ethdev: add probing finish function")
> >>> Cc: ferruh.yi...@intel.com
> >>> Cc: tho...@monjalon.net
> >>> Signed-off-by: Gaetan Rivet <gr...@u256.net>
> >>
> >> <...>
> >>
> >>> @@ -325,10 +346,17 @@ do_eth_dev_ring_create(const char *name,
> >>> data->kdrv = RTE_KDRV_NONE;
> >>> data->numa_node = numa_node;
> >>>
> >>> - /* finally assign rx and tx ops */
> >>> + /* assign rx and tx ops */
> >>> eth_dev->rx_pkt_burst = eth_ring_rx;
> >>> eth_dev->tx_pkt_burst = eth_ring_tx;
> >>>
> >>> + /* finally set the rte_device pointer in eth_dev. */
> >>> + eth_dev->device = ring_device_from_name(name);
> >>> + if (eth_dev->device == NULL) {
> >>> + rte_errno = ENODEV;
> >>> + goto error;
> >>> + }
> >>> +
> >>> rte_eth_dev_probing_finish(eth_dev);
> >>> *eth_dev_p = eth_dev;
> >>
> >> Why not move the 'rte_eth_dev_probing_finish()' to the
> >> 'rte_pmd_ring_probe()',
> >> below where 'eth_dev->device' set?
> >
> > Hi Ferruh,
> >
> > Sure it would work. The reason I did it this way is two-fold:
> >
> > * I disliked having two places where eth_dev->device was conditionally
> > set. It makes it harder to read rte_pmd_ring_probe.
>
> Agree, what about using a 'goto' to have the assignment and
> 'rte_eth_dev_probing_finish()' in a single place?
> But check seems needed since creation may failed at that stage, if you think
> better check can be done on 'ret' instead of 'eth_dev'...
>
> >
> > * I was actually thinking, doing this patch, that we should modify
> > rte_eth_dev_allocate() to take an rte_device as parameter, as all
> > eth_dev are meant to be backed by an rte_device. Keeping this in
> > mind, I meant to move writing the pointer closer to the
> > rte_eth_dev_allocate() call.
>
> That is a bigger change, may affect many (if not all) PMDs, so I think this
> can
> be considered when that change is available.
>
> And although that change may fix the issues that 'eth_dev->device' is not set,
> which we had a few times before, not sure it worth to change all PMDs and
> ethdev
> API directly couple with rte_device, instead of PMD being the glue. Can be
> discussed more on its own patch.
>
> >
> > But you are right that it is needlessly verbose, using
> > vdev_bus->find_device() to do this stuff. I'm ok with changing it as you
> > described if you prefer.
> >
>
> That was the concern, that is too much code to take a value which is already
> available a few level up the stack.
Ok, future-proofing is a bad habit so let's not do it.
I'm not a fan of the goto for the 'happy path' though. Another simple
way would be to bring the vdev pointer with me as we go down the stack.
I will send a v2 shortly, if it's too ugly to move the pointer down I'll
use the goto, or if you tell me you'd prefer it.
--
Gaëtan
