Re: [Xen-devel] [PATCH v2 30/48] xen/sched: introduce unit_runnable_state()

[Jan Beulich <jbeulich@xxxxxxxx>]

On 09.08.2019 16:58, Juergen Gross wrote:
> --- a/xen/common/schedule.c
> +++ b/xen/common/schedule.c
> @@ -266,7 +266,7 @@ static inline void sched_unit_runstate_change(struct 
> sched_unit *unit,
>      struct vcpu *v = unit->vcpu_list;
>  
>      if ( running )
> -        vcpu_runstate_change(v, RUNSTATE_running, new_entry_time);
> +        vcpu_runstate_change(v, v->new_state, new_entry_time);

Strictly speaking this is wrong when there's no actual state
change, as the state entry time then shouldn't change. Quite
possibly this would be merely a cosmetic issue though.

> --- a/xen/include/xen/sched-if.h
> +++ b/xen/include/xen/sched-if.h
> @@ -75,6 +75,20 @@ static inline bool unit_runnable(const struct sched_unit 
> *unit)
>      return vcpu_runnable(unit->vcpu_list);
>  }
>  
> +static inline bool unit_runnable_state(const struct sched_unit *unit)
> +{
> +    struct vcpu *v;
> +    bool runnable;
> +
> +    v = unit->vcpu_list;
> +    runnable = vcpu_runnable(v);
> +
> +    v->new_state = runnable ? RUNSTATE_running
> +                            : (v->pause_flags & VPF_blocked)
> +                              ? RUNSTATE_blocked : RUNSTATE_offline;
> +    return runnable;
> +}

Especially for understanding the (correctness of the) credit1
changes it would be rather helpful if once again this function
actually iterated over all vCPU-s right away (even if there's
only one per unit right now), to see how their varying states
get combined.

> --- a/xen/include/xen/sched.h
> +++ b/xen/include/xen/sched.h
> @@ -174,6 +174,7 @@ struct vcpu
>          XEN_GUEST_HANDLE(vcpu_runstate_info_compat_t) compat;
>      } runstate_guest; /* guest address */
>  #endif
> +    int              new_state;

I realize its counterpart (wrongly) is plain int in the public
interface - I think it should be unsigned int here and uint32_t
there. I'm pondering whether to do a swipe across all public
headers to replace all uses of plain int (and alike) with
fixed width types.

Jan

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