On 12.08.2017 00:38, Cong Wang wrote:
On Fri, Aug 11, 2017 at 1:36 PM, Konstantin Khlebnikov
<khlebni...@yandex-team.ru> wrote:
On 11.08.2017 23:18, Cong Wang wrote:
On Thu, Aug 10, 2017 at 2:31 AM, Konstantin Khlebnikov
<khlebni...@yandex-team.ru> wrote:
In previous API tcf_destroy_chain() could be called several times and
some schedulers like hfsc and atm use that. In new API tcf_block_put()
frees block but leaves stale pointer, second call will free it once
again.
Which call path do we call tcf_block_put() for multiple times on
the same block? Please be specific, it is not obvious.
For example in hfsc_destroy_qdisc() since
a4aebb83cf0da0363684f1c339f7e6149a3e74c1
second time in hfsc_destroy_class() called from it.
Actually, I see the same pattern in all classy qdiscs.
Good find! But that means we can just move it up??
Something like (PoC only, not even compile):
This should work, I suppose.
But this approach requires careful review for all qdisc, mine is completely
mechanical.
diff --git a/net/sched/sch_hfsc.c b/net/sched/sch_hfsc.c
index b52f74610dc7..c7db8060e8ef 100644
--- a/net/sched/sch_hfsc.c
+++ b/net/sched/sch_hfsc.c
@@ -1099,7 +1099,6 @@ hfsc_destroy_class(struct Qdisc *sch, struct
hfsc_class *cl)
{
struct hfsc_sched *q = qdisc_priv(sch);
- tcf_block_put(cl->block);
qdisc_destroy(cl->qdisc);
gen_kill_estimator(&cl->rate_est);
if (cl != &q->root)
@@ -1243,8 +1242,10 @@ hfsc_put_class(struct Qdisc *sch, unsigned long arg)
{
struct hfsc_class *cl = (struct hfsc_class *)arg;
- if (--cl->refcnt == 0)
+ if (--cl->refcnt == 0) {
+ tcf_block_put(cl->block);
hfsc_destroy_class(sch, cl);
+ }
}
static unsigned long
