netdev - Re: [net PATCH v2] net: sched: lock imbalance in hhf qdisc

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Date:	Fri, 2 May 2014 01:26:20 -0700
From:	Terry Lam <vtlam@...gle.com>
To:	John Fastabend <john.fastabend@...il.com>
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	Linux Netdev List <netdev@...r.kernel.org>,
	Eric Dumazet <edumazet@...gle.com>
Subject: Re: [net PATCH v2] net: sched: lock imbalance in hhf qdisc

Thanks a lot for the fix, John and Eric!

Regards,
Terry

On Thu, May 1, 2014 at 9:23 AM, John Fastabend <john.fastabend@...il.com> wrote:
> hhf_change() takes the sch_tree_lock and releases it but misses the
> error cases. Fix the missed case here.
>
> To reproduce try a command like this,
>
> # tc qdisc change dev p3p2 root hhf quantum 40960 non_hh_weight 300000
>
> Signed-off-by: John Fastabend <john.r.fastabend@...el.com>
> ---
>  net/sched/sch_hhf.c |   11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/net/sched/sch_hhf.c b/net/sched/sch_hhf.c
> index edee03d..6e957c3 100644
> --- a/net/sched/sch_hhf.c
> +++ b/net/sched/sch_hhf.c
> @@ -553,11 +553,6 @@ static int hhf_change(struct Qdisc *sch, struct nlattr *opt)
>         if (err < 0)
>                 return err;
>
> -       sch_tree_lock(sch);
> -
> -       if (tb[TCA_HHF_BACKLOG_LIMIT])
> -               sch->limit = nla_get_u32(tb[TCA_HHF_BACKLOG_LIMIT]);
> -
>         if (tb[TCA_HHF_QUANTUM])
>                 new_quantum = nla_get_u32(tb[TCA_HHF_QUANTUM]);
>
> @@ -567,6 +562,12 @@ static int hhf_change(struct Qdisc *sch, struct nlattr *opt)
>         non_hh_quantum = (u64)new_quantum * new_hhf_non_hh_weight;
>         if (non_hh_quantum > INT_MAX)
>                 return -EINVAL;
> +
> +       sch_tree_lock(sch);
> +
> +       if (tb[TCA_HHF_BACKLOG_LIMIT])
> +               sch->limit = nla_get_u32(tb[TCA_HHF_BACKLOG_LIMIT]);
> +
>         q->quantum = new_quantum;
>         q->hhf_non_hh_weight = new_hhf_non_hh_weight;
>
>
--
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