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Re: [PATCH v2] xen: rework error handling in vcpu_create
- To: Jan Beulich <jbeulich@xxxxxxxx>
- From: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>
- Date: Tue, 5 Aug 2025 05:06:30 -0400
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Anthony PERARD <anthony.perard@xxxxxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, "Julien Grall" <julien@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, "Dario Faggioli" <dfaggioli@xxxxxxxx>, Juergen Gross <jgross@xxxxxxxx>, "George Dunlap" <gwd@xxxxxxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Tue, 05 Aug 2025 09:06:57 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 8/5/25 03:44, Jan Beulich wrote:
> On 04.08.2025 18:57, Stewart Hildebrand wrote:
>> On 8/4/25 03:57, Jan Beulich wrote:
>>> On 01.08.2025 22:24, Stewart Hildebrand wrote:
>>>> @@ -839,6 +839,9 @@ void sched_destroy_vcpu(struct vcpu *v)
>>>> {
>>>> struct sched_unit *unit = v->sched_unit;
>>>>
>>>> + if ( !unit )
>>>> + return;
>>>> +
>>>> kill_timer(&v->periodic_timer);
>>>> kill_timer(&v->singleshot_timer);
>>>> kill_timer(&v->poll_timer);
>>>
>>> What if it's the 2nd error path in sched_init_vcpu() that is taken?
^^ This ^^ is what I'm confused about
>>> Then we
>>> might take this path (just out of context here)
>>>
>>> if ( unit->vcpu_list == v )
>>> {
>>> rcu_read_lock(&sched_res_rculock);
>>>
>>> sched_remove_unit(vcpu_scheduler(v), unit);
>>> sched_free_udata(vcpu_scheduler(v), unit->priv);
>>>
>>> and at least Credit1's hook doesn't look to be safe against being passed
>>> NULL.
>>> (Not to speak of the risk of unit->priv being used elsewhere while cleaning
>>> up.)
>>
>>
>> Are you referring to this error path in sched_init_vcpu?
>
> No, given the context I thought it was clear that I was referring to
>
> static void cf_check
> csched_free_udata(const struct scheduler *ops, void *priv)
> {
> struct csched_unit *svc = priv;
>
> BUG_ON( !list_empty(&svc->runq_elem) );
>
> (i.e. particularly this BUG_ON()).
The comment about credit1 was clear
|
