netdev - RE: [patch net v2 1/4] net/sched: Change tc_action refcnt and bindcnt to atomic

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Message-ID: <VI1PR0501MB21437552565B68DC71A7DEE1AB4D0@VI1PR0501MB2143.eurprd05.prod.outlook.com>
Date:   Wed, 18 Oct 2017 01:03:31 +0000
From:   Chris Mi <chrism@...lanox.com>
To:     Cong Wang <xiyou.wangcong@...il.com>
CC:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Lucas Bates <lucasb@...atatu.com>,
        Jiri Pirko <jiri@...nulli.us>,
        David Miller <davem@...emloft.net>
Subject: RE: [patch net v2 1/4] net/sched: Change tc_action refcnt and bindcnt
 to atomic

> -----Original Message-----
> From: Cong Wang [mailto:xiyou.wangcong@...il.com]
> Sent: Tuesday, October 17, 2017 11:53 PM
> To: Chris Mi <chrism@...lanox.com>
> Cc: Linux Kernel Network Developers <netdev@...r.kernel.org>; Jamal Hadi
> Salim <jhs@...atatu.com>; Lucas Bates <lucasb@...atatu.com>; Jiri Pirko
> <jiri@...nulli.us>; David Miller <davem@...emloft.net>
> Subject: Re: [patch net v2 1/4] net/sched: Change tc_action refcnt and
> bindcnt to atomic
> 
> On Mon, Oct 16, 2017 at 6:14 PM, Chris Mi <chrism@...lanox.com> wrote:
> > I don't think this bug were introduced by above two commits only.
> > Actually, this bug were introduced by several commits, at least the
> following:
> > 1. refcnt and bindcnt are not atomic
> 
> Nope, it is perfectly okay with non-atomic as long as no parallel, and without
> RCU callback they are perfectly serialized by RTNL.
Agree.
> 
> 
> > 2. passing actions using list instead of arrays (I think initially we
> > are using arrays)
> 
> We are discussing patch 1/4, this is patch 2/4, so irrelevant.
Agree.
> 
> 
> > 3. using RCU callbacks
> 
> This introduces problem 1.
I think this patch set only fixes one problem, that's the race and the panic.
What do you mean by problem 1.
> 
> 
> > So instead of blaming the latest commit, it is better to say it is a pre-git error.
> 
> You are wrong.
OK, you are right. But could I know what's your suggestion for this patch set?
1. reject it?
2. change the "Fixes" as you suggested?
3. something else?

Thanks,
Chris