Re: rte_bus_probe() does not exit on error

[Thomas Monjalon <thomas@monjalon.net>]

Hello,

02/05/2022 23:20, McDaniel, Timothy:
> Hello DPDK community,
> 
> I am following up on a question/comment that I submitted on April 18, for which
> I have not received any responses. See the original comment below for context.
> 
> Are there objections to modifying the behavior of rte_bus_probe() so that it propagates
> any errors detected while processing the command line arguments? It currently ignores
> errors and continues on, always returning success instead of any error that was returned
> by the probe function.

You are suggesting to stop if probing of one device fails.
I am not sure it is a good idea, because sometimes we are OK
to proceed even if one device is missing.

We could differentiate a fatal error like parsing syntax,
and "normal error" of a device which cannot be probed in some conditions.


> > -----Original Message-----
> > Hello DPDK community,
> > 
> > We are looking into an issue where we pass an invalid command line argument
> > to a vdev, and we print out an error message but don't exit.  This is an issue with
> > all of the command line options that we handle in dlb2_parse_params().  In a
> > nutshell, it looks like when we encounter an error in parsing, the error code is
> > propagated to event_dlb2_vdev_probe() (event_dlb2_pci_probe() for PF), which
> > is called by EAL during device probe in rte_bus_probe().  The problem is that
> > rte_bus_probe() calls the .probe function for each device but doesn't exit on
> > error:
> > 
> > if (vbus) {
> >                 ret = vbus->probe();
> >                 if (ret)
> >                         RTE_LOG(ERR, EAL, "Bus (%s) probe failed.\n", vbus->name);
> > }
> > return 0;
> > 
> > We want to exit if the command line arguments can't be parsed, so we have a
> > couple of options:
> > 
> > 
> >   1.  In the DLB PMD, if we get an error while parsing parameters, exit right
> > away.
> >   2.  Change the behavior of rte_bus_probe() so that it propagates the error,
> > which causes the program to exit due to EAL error.
> > 
> > if (vbus) {
> >                 ret = vbus->probe();
> >                 if (ret) {
> >                         RTE_LOG(ERR, EAL, "Bus (%s) probe failed.\n", vbus->name);
> >                         return ret;
> >                 }
> > }
> > return 0;
> > 
> > Any preference, or other ideas?  Option 1 is simple and contained in our code,
> > but does call rte_exit() from library code.  I'm not sure if that's really an issue
> > because we do want to exit if the DLB-specific options are malformed.  Option 2
> > is simple and seems like a better option, but requires changes outside of DLB, so
> > may be more difficult to upstream?  (There may be reasons why the error is
> > ignored for some devices).  Let me know what you think.
> > 
> > Thanks you for your comments,
> > Tim McDaniel