netdev - Re: [PATCH v2 net 2/2] net sched actions: decrement module refcount earlier

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Date:   Thu, 20 Apr 2017 06:28:19 -0400
From:   Jamal Hadi Salim <jhs@...atatu.com>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     Wolfgang Bumiller <w.bumiller@...xmox.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Lucas Bates <lucasb@...atatu.com>,
        Roman Mashak <mrv@...atatu.com>
Subject: Re: [PATCH v2 net 2/2] net sched actions: decrement module refcount
 earlier

On 17-04-19 01:25 PM, Cong Wang wrote:
> On Wed, Apr 19, 2017 at 4:32 AM, Jamal Hadi Salim <jhs@...atatu.com> wrote:
>> This solves one issue, but I am afraid the issue Cong mentioned is a
>> possibility still.
>> Lets say user did a replace and tried to also replace the cookie
>> in that transaction. The init() succeeds but the cookie allocation
>> fails. To be correct we'll have to undo the replace i.e something
>> like uninit() which will restore back the old values.
>> This is very complex and unnecessary.
>
> It is not complex once we move to RCU completely, replacement
> is merely a pointer assignment, rollback is same.
>

Nice to hear.

> It is necessary too according to the rules of RCU, as I said before, the
> current code is broken, we can't modify an existing action with RCU,
> we have to make a copy. I do have plan to make actions truly RCU,
> but I have to redesign the action API's first.

Ok ;->
Lucas: Lets work to get those test suites in.

cheers,
jamal