>>> On 23.06.15 at 09:19, <chao.p.p...@linux.intel.com> wrote:
> On Tue, Jun 16, 2015 at 08:08:34AM +0100, Jan Beulich wrote:
>> >>> On 03.06.15 at 06:53, <chao.p.p...@linux.intel.com> wrote:
>> > +int psr_set_l3_cbm(struct domain *d, unsigned int socket, uint64_t cbm)
>> > +{
>> > + unsigned int old_cos, cos;
>> > + struct psr_cat_cbm *map, *found = NULL;
>> > + struct psr_cat_socket_info *info = NULL;
>> > + int ret = get_cat_socket_info(socket, &info);
>> > +
>> > + if ( ret )
>> > + return ret;
>> > +
>> > + if ( !psr_check_cbm(info->cbm_len, cbm) )
>> > + return -EINVAL;
>> > +
>> > + old_cos = d->arch.psr_cos_ids[socket];
>> > + map = info->cos_to_cbm;
>> > +
>> > + spin_lock(&info->cbm_lock);
>> > +
>> > + for ( cos = 0; cos <= info->cos_max; cos++ )
>> > + {
>> > + /* If still not found, then keep unused one. */
>> > + if ( !found && cos != 0 && map[cos].ref == 0 )
>> > + found = map + cos;
>> > + else if ( map[cos].cbm == cbm )
>> > + {
>> > + if ( unlikely(cos == old_cos) )
>> > + {
>> > + spin_unlock(&info->cbm_lock);
>> > + return 0;
>>
>> Is this in particular, but also the surrounding "else if", correct when
>> map[cos].ref == 0?
>
> I can't see any problem now.
Further down in the function you increment found->ref, and it looks
suspicious that you return success here having found a slot possibly
having refount zero (and thus available for re-use for another CBM).
I.e. if this indeed is intended and correct, I think this needs to be
explained in a brief comment.
>> I can't seem to see map[cos].cbm getting
>> invalidated when an entry's refcount drops to zero...
>
> map[cos].cbm is not invalidated when refcount == 0 so that when a same
> cbm is requested again I don't need to write the corresponding register.
Ah, makes sense.
Jan
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