Re: [net-next] bpf: avoid hashtab deadlock with try_lock

[Tonghao Zhang]

On Wed, Nov 30, 2022 at 1:02 PM Hao Luo <haoluo@xxxxxxxxxx> wrote:
>
> On Tue, Nov 29, 2022 at 8:13 PM Hou Tao <houtao@xxxxxxxxxxxxxxx> wrote:
> >
> > On 11/30/2022 10:47 AM, Tonghao Zhang wrote:
> <...>
> > >         if (in_nmi()) {
> > >                 if (!raw_spin_trylock_irqsave(&b->raw_lock, flags))
> > >                         return -EBUSY;
> >
> > The only purpose of trylock here is to make lockdep happy and it may lead to
> > unnecessary -EBUSY error for htab operations in NMI context. I still prefer add
> > a virtual lock-class for map_locked to fix the lockdep warning. So could you use
> > separated patches to fix the potential dead-lock and the lockdep warning ? It
> > will be better you can also add a bpf selftests for deadlock problem as said before.
> >
>
> Agree with Tao here. Tonghao, could you send another version which:
>
> - separates the fix to deadlock and the fix to lockdep warning
> - includes a bpf selftest to verify the fix to deadlock
> - with bpf-specific tag: [PATCH bpf-next]
>
> There are multiple ideas on the fly in this thread, it's easy to lose
> track of what has been proposed and what change you intend to make.
Hi, I will send v2 soon. Thanks.
> Thanks,
> Hao



-- 
Best regards, Tonghao