Re: [Xen-devel] [PATCH] Scheduling groups, credit scheduler support

[Samuel Thibault <samuel.thibault@xxxxxxxxxxxxx>]

Samuel Thibault, le Fri 14 Dec 2007 17:01:28 +0000, a écrit :
> Mike D. Day, le Thu 29 Nov 2007 15:19:59 -0500, a écrit :
> > +static inline struct csched_dom *get_master_dom(struct csched_dom *d)
> > +{
> > +    if ( d->is_member )
> > +    {
> > +        if ( get_domain(d->master->dom) )
> > +            return d->master;
> > +        BUG();
> > +    }
> > +    return NULL;
> > +}
> > +
> > +static inline void rem_member_from_master(struct csched_dom *member,
> > +                                          struct csched_dom *master)
> > +{
> > +    reclaim_active_vcpus(master, member);
> > +    member->is_member = 0;
> > +    member->master = NULL;
> > +    list_del(&member->group_elem);
> > +    if (list_empty(&master->group))
> > +        master->is_master = 0;
> > +}
> 
> Mmm, isn't there a race condition between these, if somebody removes a
> member in the middle of somebody else calling master_dom() or
> get_master_dom()?

More precisely, there is one with SGRP_get_master, which doesn't take
the global scheduler lock before calling get_master_dom().

Samuel

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