Re: [Xen-users] Xen- SEDF credit scheduler

[Dario Faggioli <raistlin@xxxxxxxx>]

On Thu, 2012-03-22 at 09:32 +0100, Christine MAYAP wrote:
> +/*Simple test*/
> +
> +static void sedf_dyn_monit(const struct scheduler *ops, int cpu)
> +{
> +         uint64_t  idle_time;
> +
> +        idle_time = get_cpu_idle_time(cpu);
> +  
Ok, notice that this on its turn calls vcpu_runtime_get(), which might
try to acquire the rq spinlock.

> +        printk("[HERE]idle_time = %llu \n", idle_time);
> +
> +}
> +
>
> +static struct task_slice sedf_do_schedule(const struct scheduler
> *ops, s_time_t now, bool_t tasklet_work_scheduled)
>  {
>      int                   cpu      = smp_processor_id();
>      struct list_head     *runq     = RUNQ(cpu);
> @@ -799,6 +811,10 @@
>      struct sedf_vcpu_info *runinf, *waitinf;
>      struct task_slice      ret;
>  
> +
> +      if ( NOW() >= (10*PERIOD_MAX)) sedf_dyn_monit(ops,cpu);
> +
And here you go... I can't be 100% sure, as I only had time to give a
very quick look for now, but I smell deadlock! :-/

I might be wrong, but given how the code looks, calling
get_cpu_idle_time() from a context already holding the rq spinlock does
not seem to be a good idea.

I can't be of much more help, as I don't know what you're trying to
accomplish here, but there are few chances for your approach to be the
correct one.

There seems to be other means for getting the information you're looking
for. Again, I can't be precise and am just shooting in the dark here,
but, e.g., hypercalls (have you looked at getcpuinfo ?).

Hope I helped at least a bit,
Dario

-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-------------------------------------------------------------------
Dario Faggioli, Ph.D, http://retis.sssup.it/people/faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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