Re: [PATCH] net/sched: use spin_lock_bh() on &gact->tcf_lock

[Horatiu Vultur <horatiu.vultur@microchip.com>]

The 10/05/2023 07:46, Jamal Hadi Salim wrote:

Hi Jamal,

> On Thu, Oct 5, 2023 at 5:01 AM Chengfeng Ye <dg573847474@gmail.com> wrote:
> >
> > Hi Jakub,
> >
> > Thanks for the reply,
> >
> > I inspected the code a bit more, it seems that the TC action is called from
> > tcf_proto_ops.classify() callback, which is called from Qdisc_ops enqueue
> > callback.
> >
> > Then Qdisc enqueue callback is from
> >
> > -> __dev_queue_xmit()
> > -> __dev_xmit_skb()
> > -> dev_qdisc_enqueue()
> >
> > inside the net core. It seems that this __dev_queue_xmit() callback is
> > typically called from BH context (e.g.,  NET_TX_SOFTIRQ) with BH
> > already disabled, but sometimes also can from a work queue under
> > process context, one case is the br_mrp_test_work_expired() inside
> > net/bridge/br_mrp.c. Does it indicate that this TC action could also be
> > called with BH enable? I am not a developer so really not sure about it,
> > as the networking code is a bit long and complicated.
> 
> net/bridge/br_mrp.c seems to need some love +Cc Horatiu Vultur
> <horatiu.vultur@microchip.com>
> Maybe that code needs to run in a tasklet?
> In any case your patch is incorrect.

I am currently out traveling and it would be a little bit hard for me to
look at this right now. I can have a look after I come back in office
around mid November.
But I was wondering if this is stil an issue for MRP as Cong Wang
pointed out, the function __dev_queue_xmit is already disabling the BH.

> 
> cheers,
> jamal
> 

-- 
/Horatiu