Re: [Xen-devel] [for-4.9 PATCH] xen: credit: change an ASSERT on nr_runnable so that it makes sense.

[Julien Grall <julien.grall@xxxxxxx>]

Hi Dario,

On 13/04/17 08:49, Dario Faggioli wrote:
> Since the counter is unsigned, it's pointless/bogous to check
> for if to be above zero.
>
> Check that it is at least one before it's decremented, instead.
>
> Spotted by Coverity.
Do you have the Coverity-ID? :)

> Reported-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Signed-off-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx>
> ---
> Cc: George Dunlap <george.dunlap@xxxxxxxxxx>
> Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Cc: Julien Grall <julien.grall@xxxxxxx>
> ---
> Julien,
>
> This is very low risk, and I'd call it a bugfix in the sense that it quiesces
> coverity.
Release-Acked-by: Julien Grall <julien.grall@xxxxxxx>

> Dario
> ---
>  xen/common/sched_credit.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/xen/common/sched_credit.c b/xen/common/sched_credit.c
> index 93658dc..efdf6bf 100644
> --- a/xen/common/sched_credit.c
> +++ b/xen/common/sched_credit.c
> @@ -275,8 +275,8 @@ static inline void
>  dec_nr_runnable(unsigned int cpu)
>  {
>      ASSERT(spin_is_locked(per_cpu(schedule_data, cpu).schedule_lock));
> +    ASSERT(CSCHED_PCPU(cpu)->nr_runnable >= 1);
>      CSCHED_PCPU(cpu)->nr_runnable--;
> -    ASSERT(CSCHED_PCPU(cpu)->nr_runnable >= 0);
>  }
>
>  static inline void
Cheers,

--
Julien Grall

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