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sch_hfsc: make hfsc_qlen_notify() idempotent

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hfsc_qlen_notify() is not idempotent either and not friendly
to its callers, like fq_codel_dequeue(). Let's make it idempotent
to ease qdisc_tree_reduce_backlog() callers' life:

1. update_vf() decreases cl->cl_nactive, so we can check whether it is
non-zero before calling it.

2. eltree_remove() always removes RB node cl->el_node, but we can use
   RB_EMPTY_NODE() + RB_CLEAR_NODE() to make it safe.

Reported-by: Gerrard Tai <gerrard.tai@starlabs.sg>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250403211033.166059-4-xiyou.wangcong@gmail.com
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Cong Wang 2025-04-03 14:10:25 -07:00 committed by Paolo Abeni
parent df008598b3
commit 51eb3b6554
1 changed files with 6 additions and 2 deletions
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8
net/sched/sch_hfsc.c
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@ -203,7 +203,10 @@ eltree_insert(struct hfsc_class *cl)
static inline void static inline void
eltree_remove(struct hfsc_class *cl) eltree_remove(struct hfsc_class *cl)
{ {
rb_erase(&cl->el_node, &cl->sched->eligible); if (!RB_EMPTY_NODE(&cl->el_node)) {
rb_erase(&cl->el_node, &cl->sched->eligible);
RB_CLEAR_NODE(&cl->el_node);
}
} }
static inline void static inline void
@ -1220,7 +1223,8 @@ hfsc_qlen_notify(struct Qdisc *sch, unsigned long arg)
/* vttree is now handled in update_vf() so that update_vf(cl, 0, 0) /* vttree is now handled in update_vf() so that update_vf(cl, 0, 0)
* needs to be called explicitly to remove a class from vttree. * needs to be called explicitly to remove a class from vttree.
*/ */
update_vf(cl, 0, 0); if (cl->cl_nactive)
update_vf(cl, 0, 0);
if (cl->cl_flags & HFSC_RSC) if (cl->cl_flags & HFSC_RSC)
eltree_remove(cl); eltree_remove(cl);
} }