Re: [PATCH 05/14] net: sched: always take reference to action

Jiri Pirko
2018-05-15T08:59:05Z

Mon, May 14, 2018 at 08:49:07PM CEST, vladbu@mellanox.com wrote:
>
>On Mon 14 May 2018 at 16:23, Jiri Pirko <jiri@resnulli.us> wrote:
>> Mon, May 14, 2018 at 04:27:06PM CEST, vladbu@mellanox.com wrote:
>>>Without rtnl lock protection it is no longer safe to use pointer to tc
>>>action without holding reference to it. (it can be destroyed concurrently)
>>>
>>>Remove unsafe action idr lookup function. Instead of it, implement safe tcf
>>>idr check function that atomically looks up action in idr and increments
>>>its reference and bind counters.
>>>
>>>Implement both action search and check using new safe function.
>>>
>>>Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
>>>---
>>> net/sched/act_api.c | 38 ++++++++++++++++----------------------
>>> 1 file changed, 16 insertions(+), 22 deletions(-)
>>>
>>>diff --git a/net/sched/act_api.c b/net/sched/act_api.c
>>>index 1331beb..9459cce 100644
>>>--- a/net/sched/act_api.c
>>>+++ b/net/sched/act_api.c
>>>@@ -284,44 +284,38 @@ int tcf_generic_walker(struct tc_action_net *tn, struct sk_buff *skb,
>>> }
>>> EXPORT_SYMBOL(tcf_generic_walker);
>>>
>>>-static struct tc_action *tcf_idr_lookup(u32 index, struct tcf_idrinfo *idrinfo)
>>>+bool __tcf_idr_check(struct tc_action_net *tn, u32 index, struct tc_action **a,
>>>+ int bind)
>>> {
>>>- struct tc_action *p = NULL;
>>>+ struct tcf_idrinfo *idrinfo = tn->idrinfo;
>>>+ struct tc_action *p;
>>>
>>> spin_lock_bh(&idrinfo->lock);
>>
>> Why "_bh" variant is necessary here?
>
>It is not my code.

Yeah, yet still I wonder :)