Re: [PATCH 2/7] xen: sched_rt: implement the .free_pdata hook

[George Dunlap <george.dunlap@eu.citrix.com>]

On 03/16/2015 05:04 PM, Dario Faggioli wrote:
> which is called by cpu_schedule_down(), and is necessary
> for resetting the spinlock pointers in schedule_data from
> the RTDS global runqueue lock, back to the default _lock
> fields in the struct.
> 
> Not doing so causes Xen to explode, e.g., when removing
> pCPUs from an RTDS cpupool and assigning them to another
> one.
> 
> Signed-off-by: Dario Faggioli <dario.faggioli@citrix.com>
> Cc: George Dunlap <george.dunlap@eu.citrix.com>
> Cc: Meng Xu <xumengpanda@gmail.com>
> Cc: Jan Beulich <JBeulich@suse.com>
> Cc: Keir Fraser <keir@xen.org>

Reviewed-by: George Dunlap <george.dunlap@eu.citrix.com>

> ---
>  xen/common/sched_rt.c |   18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/xen/common/sched_rt.c b/xen/common/sched_rt.c
> index 055a50f..3e37e62 100644
> --- a/xen/common/sched_rt.c
> +++ b/xen/common/sched_rt.c
> @@ -444,6 +444,23 @@ rt_alloc_pdata(const struct scheduler *ops, int cpu)
>      return (void *)1;
>  }
>  
> +static void
> +rt_free_pdata(const struct scheduler *ops, void *pcpu, int cpu)
> +{
> +    struct rt_private *prv = rt_priv(ops);
> +    struct schedule_data *sd = &per_cpu(schedule_data, cpu);
> +    unsigned long flags;
> +
> +    spin_lock_irqsave(&prv->lock, flags);
> +
> +    /* Move spinlock back to the default lock */
> +    ASSERT(sd->schedule_lock == &prv->lock);
> +    ASSERT(!spin_is_locked(&sd->_lock));
> +    sd->schedule_lock = &sd->_lock;
> +
> +    spin_unlock_irqrestore(&prv->lock, flags);
> +}
> +
>  static void *
>  rt_alloc_domdata(const struct scheduler *ops, struct domain *dom)
>  {
> @@ -1090,6 +1107,7 @@ const struct scheduler sched_rtds_def = {
>      .init           = rt_init,
>      .deinit         = rt_deinit,
>      .alloc_pdata    = rt_alloc_pdata,
> +    .free_pdata     = rt_free_pdata,
>      .alloc_domdata  = rt_alloc_domdata,
>      .free_domdata   = rt_free_domdata,
>      .init_domain    = rt_dom_init,
>