netdev - Re: [RFC PATCH net-next] net: sched: flower: refactor reoffload for concurrent access

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Date:   Thu, 18 Apr 2019 11:15:42 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Vlad Buslov <vladbu@...lanox.com>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "jhs@...atatu.com" <jhs@...atatu.com>,
        "xiyou.wangcong@...il.com" <xiyou.wangcong@...il.com>,
        "jiri@...nulli.us" <jiri@...nulli.us>,
        "davem@...emloft.net" <davem@...emloft.net>
Subject: Re: [RFC PATCH net-next] net: sched: flower: refactor reoffload for
 concurrent access

On Thu, 18 Apr 2019 18:13:37 +0000, Vlad Buslov wrote:
> On Thu 18 Apr 2019 at 21:02, Jakub Kicinski <jakub.kicinski@...ronome.com> wrote:
> > On Thu, 18 Apr 2019 17:58:26 +0000, Vlad Buslov wrote:  
> >> On Thu 18 Apr 2019 at 20:46, Jakub Kicinski <jakub.kicinski@...ronome.com> wrote:  
> >> > On Thu, 18 Apr 2019 16:33:22 +0000, Vlad Buslov wrote:    
> >> >> Considering this, I tried to improve my solution to remove possibility
> >> >> of multiple adds of same filter and it seems to me that it would be
> >> >> enough to move hw_filters list management in flower offloads functions:
> >> >> add filter to list while holding rtnl lock in fl_hw_replace_filter() and
> >> >> remove it from list while holding rtnl lock in fl_hw_destroy_filter().
> >> >> What do you think?    
> >> >
> >> > Sounds good for now, but I presume the plan is to get rid of rtnl
> >> > around the driver call.. at which point we would switch to a rwlock? :)    
> >> 
> >> Yes, but I would like the lock to be in cls hw offloads API
> >> (tc_setup_cb_replace(), etc) and not in flower itself. That would also
> >> solve deadlock issue and make code reusable for any further unlocked
> >> classifiers implementations.  
> >
> > And then the HW list goes along with it into the common code?
> > That'd be quite nice.  
> 
> The goal is to have a lock in tcf_block and use it synchronize cb_list
> and all related counters (offloadcnt, etc). Now I also want to use it to
> protect hw_filters list and prevent the double-add issue. Meanwhile rtnl
> lock can do the job.

SGTM 👍