Re: [Xen-devel] [PATCH v11 5/9] x86: dynamically attach/detach QoS monitoring service for a guest

["Xu, Dongxiao" <dongxiao.xu@xxxxxxxxx>]

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: Friday, June 20, 2014 11:08 PM
> To: Xu, Dongxiao
> Cc: andrew.cooper3@xxxxxxxxxx; Ian.Campbell@xxxxxxxxxx;
> George.Dunlap@xxxxxxxxxxxxx; Ian.Jackson@xxxxxxxxxxxxx;
> stefano.stabellini@xxxxxxxxxxxxx; xen-devel@xxxxxxxxxxxxx;
> konrad.wilk@xxxxxxxxxx; dgdegra@xxxxxxxxxxxxx; keir@xxxxxxx
> Subject: Re: [PATCH v11 5/9] x86: dynamically attach/detach QoS monitoring
> service for a guest
> 
> >>> On 20.06.14 at 16:31, <dongxiao.xu@xxxxxxxxx> wrote:
> > +int pqos_monitor_alloc_rmid(struct domain *d)
> > +{
> > +    int rc = 0;
> > +    unsigned int rmid;
> > +
> > +    ASSERT(pqos_monitor_enabled());
> > +
> > +    spin_lock(&pqosm->pqosm_lock);
> > +
> > +    if ( d->arch.pqos_rmid > 0 )
> > +    {
> > +        rc = -EEXIST;
> > +        goto out;
> > +    }
> 
> Does this check really need to be inside the locked region? You're
> already protected against races by the domctl lock.

It seems no need any more for these qos monitor related lock. Will remove it.

Thanks,
Dongxiao

> 
> > +void pqos_monitor_free_rmid(struct domain *d)
> > +{
> > +    unsigned int rmid;
> > +
> > +    spin_lock(&pqosm->pqosm_lock);
> > +    rmid = d->arch.pqos_rmid;
> > +    /* We do not free system reserved "RMID=0" */
> > +    if ( rmid == 0 )
> > +        goto out;
> 
> Similarly here.
> 
> Jan


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