Re: [Xen-devel] What is the current state of Dom0 kernel support? / crash

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Wed, Jul 29, 2009 at 01:48:05PM -0700, Jeremy Fitzhardinge wrote:
> >>>>> The stack backtrace is a bit fuzzy; do you have CONFIG_FRAMEPOINTER 
> >>>>> enabled?  
> >>>>> And if you have CONFIG_DEBUGINFO enabled, you can map the eip c058cdcb 
> >>>>> to a specific source line (its not clear to me which pointer is NULL).
> >>>>>
> >>>>>       
> >>>>>           
> >>>> [root@dom0test linux-2.6-xen]# grep -i CONFIG_FRAMEPOINTER .config
> >>>> [root@dom0test linux-2.6-xen]# grep -i CONFIG_DEBUGINFO .config
> >>>> [root@dom0test linux-2.6-xen]# 
> >>>>
> >>>> Unfortunately those were not enabled.. I'll build a new kernel with
> >>>> CONFIG_DEBUGINFO enabled.
> >>>>
> >>>>     
> >>>>         
> >>> Actually CONFIG_DEBUG_INFO was enabled, if you meant that? 
> >>>   
> >>>       
> >> Yes, that's it.
> >>     
> >>> (gdb) x/i 0xc058cdcb
> >>>   
> >>>       
> >> Try "list *0xc058cdcb".
> >>
> >>     
> >
> > (gdb) list *0xc058cdcb
> > 0xc058cdcb is in active_evtchns (drivers/xen/events.c:237).
> > 232
> > 233     static inline unsigned long active_evtchns(unsigned int cpu,
> > 234                                                struct shared_info *sh,
> > 235                                                unsigned int idx)
> > 236     {
> > 237             return (sh->evtchn_pending[idx] &
> > 238                     cpu_evtchn_mask(cpu)[idx] &
> > 239                     ~sh->evtchn_mask[idx]);
> > 240     }
> > 241
> > (gdb)
> >
> >
> > -- Pasi
> >
> >   
> 
> Does this help?
> 

I'll try it later today. 

-- Pasi

>     J
> 
> Subject: [PATCH] xen: use proper percpu variable for cpu_evtchn_mask
> 
> cpu_evtchn_mask is a per-cpu mask of event channels, so it should
> be implemented as a proper per_cpu variable.
> 
> Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
> 
> diff --git a/drivers/xen/events.c b/drivers/xen/events.c
> index abad71b..4443b0f 100644
> --- a/drivers/xen/events.c
> +++ b/drivers/xen/events.c
> @@ -93,14 +93,11 @@ static struct irq_info irq_info[NR_IRQS];
>  static int evtchn_to_irq[NR_EVENT_CHANNELS] = {
>       [0 ... NR_EVENT_CHANNELS-1] = -1
>  };
> -struct cpu_evtchn_s {
> -     unsigned long bits[NR_EVENT_CHANNELS/BITS_PER_LONG];
> -};
> -static struct cpu_evtchn_s *cpu_evtchn_mask_p;
> -static inline unsigned long *cpu_evtchn_mask(int cpu)
> -{
> -     return cpu_evtchn_mask_p[cpu].bits;
> -}
> +
> +#define NR_EVENT_CHANNEL_LONGS       (NR_EVENT_CHANNELS/BITS_PER_LONG)
> +static DEFINE_PER_CPU(unsigned long,
> +                   cpu_evtchn_mask[NR_EVENT_CHANNEL_LONGS]) =
> +     {[0 ... NR_EVENT_CHANNEL_LONGS-1] = ~0};
>  
>  /* Xen will never allocate port zero for any purpose. */
>  #define VALID_EVTCHN(chn)    ((chn) != 0)
> @@ -223,7 +220,7 @@ static inline unsigned long active_evtchns(unsigned int 
> cpu,
>                                          unsigned int idx)
>  {
>       return (sh->evtchn_pending[idx] &
> -             cpu_evtchn_mask(cpu)[idx] &
> +             per_cpu(cpu_evtchn_mask, cpu)[idx] &
>               ~sh->evtchn_mask[idx]);
>  }
>  
> @@ -236,8 +233,8 @@ static void bind_evtchn_to_cpu(unsigned int chn, unsigned 
> int cpu)
>       cpumask_copy(irq_to_desc(irq)->affinity, cpumask_of(cpu));
>  #endif
>  
> -     __clear_bit(chn, cpu_evtchn_mask(cpu_from_irq(irq)));
> -     __set_bit(chn, cpu_evtchn_mask(cpu));
> +     __clear_bit(chn, per_cpu(cpu_evtchn_mask, cpu_from_irq(irq)));
> +     __set_bit(chn, per_cpu(cpu_evtchn_mask, cpu));
>  
>       irq_info[irq].cpu = cpu;
>  }
> @@ -253,8 +250,6 @@ static void init_evtchn_cpu_bindings(void)
>               cpumask_copy(desc->affinity, cpumask_of(0));
>       }
>  #endif
> -
> -     memset(cpu_evtchn_mask(0), ~0, sizeof(cpu_evtchn_mask(0)));
>  }
>  
>  static inline void clear_evtchn(int port)
> @@ -928,10 +923,6 @@ void __init xen_init_IRQ(void)
>  {
>       int i;
>  
> -     cpu_evtchn_mask_p = kcalloc(nr_cpu_ids, sizeof(struct cpu_evtchn_s),
> -                                 GFP_KERNEL);
> -     BUG_ON(cpu_evtchn_mask_p == NULL);
> -
>       init_evtchn_cpu_bindings();
>  
>       /* No event channels are 'live' right now. */
> 
> 

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