From mboxrd@z Thu Jan  1 00:00:00 1970
From: George Dunlap <george.dunlap@eu.citrix.com>
Subject: Re: [PATCH 1/7] xen: sched_rt: avoid ASSERT()ing on
 runq dump if there are no domains
Date: Mon, 16 Mar 2015 18:18:15 +0000
Message-ID: <55071E67.4060306@eu.citrix.com>
References: <20150316165642.10279.86684.stgit@Solace.station>
	<20150316170450.10279.38060.stgit@Solace.station>
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To: Dario Faggioli <dario.faggioli@citrix.com>, Xen-devel <xen-devel@lists.xen.org>
Cc: Keir Fraser <keir@xen.org>, Meng Xu <xumengpanda@gmail.com>, Jan Beulich <JBeulich@suse.com>
List-Id: xen-devel@lists.xenproject.org

On 03/16/2015 05:04 PM, Dario Faggioli wrote:
> being serviced by the RTDS scheduler, as that is a
> legit situation to be in: think, for instance, of a
> newly created RTDS cpupool, with no domains migrated
> to it yet.
> 
> 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>

You're not going to mention fixing a race condition while you're at it? :-)

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

> ---
>  xen/common/sched_rt.c |   10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/xen/common/sched_rt.c b/xen/common/sched_rt.c
> index df4adac..055a50f 100644
> --- a/xen/common/sched_rt.c
> +++ b/xen/common/sched_rt.c
> @@ -264,18 +264,17 @@ rt_dump(const struct scheduler *ops)
>      struct list_head *iter_sdom, *iter_svc, *runq, *depletedq, *iter;
>      struct rt_private *prv = rt_priv(ops);
>      struct rt_vcpu *svc;
> -    cpumask_t *online;
>      struct rt_dom *sdom;
>      unsigned long flags;
>  
> -    ASSERT(!list_empty(&prv->sdom));
> +    spin_lock_irqsave(&prv->lock, flags);
> +
> +    if (list_empty(&prv->sdom))
> +        goto out;
>  
> -    sdom = list_entry(prv->sdom.next, struct rt_dom, sdom_elem);
> -    online = cpupool_scheduler_cpumask(sdom->dom->cpupool);
>      runq = rt_runq(ops);
>      depletedq = rt_depletedq(ops);
>  
> -    spin_lock_irqsave(&prv->lock, flags);
>      printk("Global RunQueue info:\n");
>      list_for_each( iter, runq )
>      {
> @@ -303,6 +302,7 @@ rt_dump(const struct scheduler *ops)
>          }
>      }
>  
> +out:
>      spin_unlock_irqrestore(&prv->lock, flags);
>  }
>  
>