netdev - Re: [PATCH bpf-next 2/4] bpf: fix lockdep false positive in stackmap

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Wed, 30 Jan 2019 15:05:23 -0500
From:   Waiman Long <longman@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Alexei Starovoitov <ast@...nel.org>, davem@...emloft.net,
        daniel@...earbox.net, edumazet@...gle.com, jannh@...gle.com,
        netdev@...r.kernel.org, kernel-team@...com
Subject: Re: [PATCH bpf-next 2/4] bpf: fix lockdep false positive in stackmap

On 01/30/2019 02:44 PM, Peter Zijlstra wrote:
> On Wed, Jan 30, 2019 at 11:30:41AM -0800, Alexei Starovoitov wrote:
>> On Wed, Jan 30, 2019 at 11:15:30AM +0100, Peter Zijlstra wrote:
>>> On Tue, Jan 29, 2019 at 08:04:56PM -0800, Alexei Starovoitov wrote:
>>>> Lockdep warns about false positive:
>>> This is not a false positive, and you probably also need to use
>>> down_read_non_owner() to match this up_read_non_owner().
>>>
>>> {up,down}_read() and {up,down}_read_non_owner() are not only different
>>> in the lockdep annotation; there is also optimistic spin stuff that
>>> relies on 'owner' tracking.
>> Can you point out in the code the spin bit?
> Hurmph, looks like you're right. I got lost in that stuff again. I hate
> that rwsem code :/

It is actually related to how the lockdep code track if a lock is
acquired or released. It is not actually related to how the rwsem code work.

>
> Rewriting that all is on the todo list somewhere, but it's far down :/
>

I am actually planning to rewrite it. Hopefully, I can send out the
patch soon.

Cheers,
Longman