[Olsr-dev] olsr strange behaving / nearly no outgoing packets [partly solved]

[Henning Rogge]

Yes, it is...

and its definitely a compiler bug! You should file a bug report.

I do not like the volatile thing at all, because it prevents the
working compilers from optimizing the variables away.

Henning Rogge

On Mon, Aug 13, 2012 at 5:17 PM, Lars Kruse <(spam-protected)> wrote:
> Hi,
>
>> > Besides this approach I don't see any other options for further
>> > investigations. Or what would you say?
>>
>> Maybe we could just add a new variable and calculate the return value in
>> two steps. Most compilers should optimize the variable away anyways.
>>
>> uint32_t ms;
>>
>> ....
>>
>> t = (tv.tv_sec  - first_tv.tv_sec)  * 1000;
>> ms = (tv.tv_usec - first_tv.tv_usec) / 1000;
>>
>> return t + ms;
>> }
>>
>> Does this help ?
>
> Almost - but thanks for the hint!
>
>
> The following patch fixes it:
>
> --- olsrd-0.6.2.orig/src/scheduler.c    2012-08-13 14:59:43.000000000 +0200
> +++ olsrd-0.6.2/src/scheduler.c 2012-08-13 15:00:46.000000000 +0200
> @@ -87,7 +87,7 @@ static uint32_t
>  olsr_times(void)
>  {
>    struct timeval tv;
> -  uint32_t t;
> +  volatile uint32_t t, ms;
>
>    if (gettimeofday(&tv, NULL) != 0) {
>      olsr_exit("OS clock is not working, have to shut down OLSR", 1);
> @@ -114,7 +114,9 @@ olsr_times(void)
>      return t;
>    }
>    last_tv = tv;
> -  return (tv.tv_sec - first_tv.tv_sec) * 1000 + (tv.tv_usec -
> first_tv.tv_usec) / 1000;
> +  t = (tv.tv_sec - first_tv.tv_sec) * 1000;
> +  ms = (tv.tv_usec - first_tv.tv_usec) / 1000;
> +  return t + ms;
>  }
>
>  /**
>
>
>
> It seems that the "volatile" keyword prevents the compiler from doing evil
> things. This is ugly! :(
>
> cheers,
> Lars
>
> --
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> (spam-protected)
> https://lists.olsr.org/mailman/listinfo/olsr-dev



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