Re: [dpdk-dev] [PATCH] eal/linux: fix return after alarm registration failure

[Thomas Monjalon <thomas@monjalon.net>]

26/06/2019 14:52, Burakov, Anatoly:
> On 26-Jun-19 1:36 PM, Bruce Richardson wrote:
> > On Wed, Jun 26, 2019 at 01:55:53PM +0200, Thomas Monjalon wrote:
> >> 26/06/2019 13:43, Burakov, Anatoly:
> >>> On 26-Jun-19 12:39 PM, David Marchand wrote:
> >>>> On Wed, Jun 26, 2019 at 1:36 PM Thomas Monjalon <thomas@monjalon.net> wrote:
> >>>>
> >>>>> 26/06/2019 13:20, David Marchand:
> >>>>>> On Wed, Jun 26, 2019 at 12:41 PM Thomas Monjalon <thomas@monjalon.net>
> >>>>>> wrote:
> >>>>>>
> >>>>>>> When adding an alarm, if an error happen when registering
> >>>>>>> the common alarm callback, it is not considered as a major failure.
> >>>>>>> The alarm is then inserted in the list.
> >>>>>>> However it was returning an error code after inserting the alarm.
> >>>>>>>
> >>>>>>> The error code is reset to 0 so the behaviour and the return code
> >>>>>>> are consistent.
> >>>>>>> Other return code related lines are cleaned up for easier
> >>>>> understanding.
> >>>>>>>
> >>>>> [...]
> >>>>>>> --- a/lib/librte_eal/linux/eal/eal_alarm.c
> >>>>>>> +++ b/lib/librte_eal/linux/eal/eal_alarm.c
> >>>>>>>           if (!handler_registered) {
> >>>>>>> -               ret |= rte_intr_callback_register(&intr_handle,
> >>>>>>> +               ret = rte_intr_callback_register(&intr_handle,
> >>>>>>>                                   eal_alarm_callback, NULL);
> >>>>>>> -               handler_registered = (ret == 0) ? 1 : 0;
> >>>>>>> +               if (ret == 0)
> >>>>>>> +                       handler_registered = 1;
> >>>>>>> +               else
> >>>>>>> +                       /* not fatal, callback can be registered later
> >>>>> */
> >>>>>>> +                       ret = 0;
> >>>>>>>           }
> >>>>>>
> >>>>>> Well, then it means that you don't want to touch ret at all.
> >>>>>> How about:
> >>>>>> if (rte_intr_callback_register(&intr_handle,
> >>>>>>                                  eal_alarm_callback, NULL) == 0)
> >>>>>>           handler_registered = 1;
> >>>>>>
> >>>>>> ?
> >>>>>
> >>>>> Too much simple :)
> >>>>>
> >>>>> I think we try to avoid calling a function in a "if"
> >>>>> per coding style.
> >>>>> And my proposal has the benefit of offering a comment
> >>>>> about the non-fatal error.
> >>>>>
> >>>>
> >>>> /* not fatal, callback can be registered later */
> >>>> if (rte_intr_callback_register(&intr_handle,
> >>>>                                 eal_alarm_callback, NULL) == 0)
> >>>>          handler_registered = 1;
> >>>>
> >>>
> >>> I prefer the original. It's more explicit and conveys the intention
> >>> better. Did i break the tie? :)
> >>
> >> I was going to send a v2 with David's suggestion.
> >> Now I'm confused.
> >>
> > I always tend to prefer shorter versions, so +1 for v2 (does that make it a
> > v3? :-) )
> > 
> > /Bruce
> > 
> 
> OK, but then the suggested comment needs to be fixed. It makes it seem 
> like registering the handler is the "non fatal" part. Perhaps something 
> like:
> 
> /* failed register is not a fatal error - callback can be registered 
> later */

Of course! I had prepared this:
/* registration can fail, callback can be registered later */