Messages in this thread | | | Date | Fri, 31 Jan 2020 11:20:59 +0100 | From | Oleksandr Natalenko <> | Subject | Re: [PATCH BUGFIX 3/6] block, bfq: get extra ref to prevent a queue from being freed during a group move |
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Hello.
On 31.01.2020 10:24, Paolo Valente wrote: > In bfq_bfqq_move(), the bfq_queue, say Q, to be moved to a new group > may happen to be deactivated in the scheduling data structures of the > source group (and then activated in the destination group). If Q is > referred only by the data structures in the source group when the > deactivation happens, then Q is freed upon the deactivation. > > This commit addresses this issue by getting an extra reference before > the possible deactivation, and releasing this extra reference after Q > has been moved. > > Tested-by: Chris Evich <cevich@redhat.com> > Signed-off-by: Paolo Valente <paolo.valente@linaro.org> > --- > block/bfq-cgroup.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c > index e1419edde2ec..8ab7f18ff8cb 100644 > --- a/block/bfq-cgroup.c > +++ b/block/bfq-cgroup.c > @@ -651,6 +651,12 @@ void bfq_bfqq_move(struct bfq_data *bfqd, struct > bfq_queue *bfqq, > bfq_bfqq_expire(bfqd, bfqd->in_service_queue, > false, BFQQE_PREEMPTED); > > + /* > + * get extra reference to prevent bfqq from being freed in > + * next possible deactivate > + */ > + bfqq->ref++;
Shouldn't this be hidden under some macro (bfq_get_queue_ref(), for instance) and also converted from int into refcount_t?
> + > if (bfq_bfqq_busy(bfqq)) > bfq_deactivate_bfqq(bfqd, bfqq, false, false); > else if (entity->on_st) > @@ -670,6 +676,8 @@ void bfq_bfqq_move(struct bfq_data *bfqd, struct > bfq_queue *bfqq, > > if (!bfqd->in_service_queue && !bfqd->rq_in_driver) > bfq_schedule_dispatch(bfqd); > + /* release extra ref taken above */ > + bfq_put_queue(bfqq); > } > > /**
-- Oleksandr Natalenko (post-factum)
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