(better CC netdev)
Paul Menage wrote:
> cls_cgroup: read classid atomically in classifier
>
> Avoid reading the unsynchronized value cs->classid multiple times,
> since it could change concurrently from non-zero to zero; this would
> result in the classifier returning a positive result with a bogus
> (zero) classid.
>
This patch looks nice. It also narrows rcu read section.
Reviewed-by: Li Zefan <lizf@xxxxxxxxxxxxxx>
> Signed-off-by: Paul Menage <menage@xxxxxxxxxx>
>
> ---
>
> net/sched/cls_cgroup.c | 22 +++++++++++-----------
> 1 files changed, 11 insertions(+), 11 deletions(-)
>
> diff --git a/net/sched/cls_cgroup.c b/net/sched/cls_cgroup.c
> index 1ab4542..4ece6e0 100644
> --- a/net/sched/cls_cgroup.c
> +++ b/net/sched/cls_cgroup.c
> @@ -98,8 +98,7 @@ static int cls_cgroup_classify(struct sk_buff *skb, struct tcf_proto *tp,
> struct tcf_result *res)
> {
> struct cls_cgroup_head *head = tp->root;
> - struct cgroup_cls_state *cs;
> - int ret = 0;
> + u32 classid;
>
> /*
> * Due to the nature of the classifier it is required to ignore all
> @@ -115,17 +114,18 @@ static int cls_cgroup_classify(struct sk_buff *skb, struct tcf_proto *tp,
> return -1;
>
> rcu_read_lock();
> - cs = task_cls_state(current);
> - if (cs->classid && tcf_em_tree_match(skb, &head->ematches, NULL)) {
> - res->classid = cs->classid;
> - res->class = 0;
> - ret = tcf_exts_exec(skb, &head->exts, res);
> - } else
> - ret = -1;
> -
> + classid = task_cls_state(current)->classid;
> rcu_read_unlock();
>
> - return ret;
> + if (!classid)
> + return -1;
> +
> + if (!tcf_em_tree_match(skb, &head->ematches, NULL))
> + return -1;
> +
> + res->classid = classid;
> + res->class = 0;
> + return tcf_exts_exec(skb, &head->exts, res);
> }
>
> static unsigned long cls_cgroup_get(struct tcf_proto *tp, u32 handle)
>
>
>
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