netdev - Re: [PATCH v2 bpf] bpf: fix lockdep false positive in stackmap

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Date:   Mon, 11 Feb 2019 08:35:22 -0800
From:   Eric Dumazet <edumazet@...gle.com>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        David Miller <davem@...emloft.net>,
        Peter Zijlstra <peterz@...radead.org>, longman@...hat.com,
        Jann Horn <jannh@...gle.com>, netdev <netdev@...r.kernel.org>,
        kernel-team <kernel-team@...com>
Subject: Re: [PATCH v2 bpf] bpf: fix lockdep false positive in stackmap

On Mon, Feb 11, 2019 at 7:39 AM Daniel Borkmann <daniel@...earbox.net> wrote:
>
> On 02/10/2019 09:52 PM, Alexei Starovoitov wrote:
> > Lockdep warns about false positive:
> > [   11.211460] ------------[ cut here ]------------
> > [   11.211936] DEBUG_LOCKS_WARN_ON(depth <= 0)
> > [   11.211985] WARNING: CPU: 0 PID: 141 at ../kernel/locking/lockdep.c:3592 lock_release+0x1ad/0x280
> > [   11.213134] Modules linked in:
> > [   11.214954] RIP: 0010:lock_release+0x1ad/0x280
> > [   11.223508] Call Trace:
> > [   11.223705]  <IRQ>
> > [   11.223874]  ? __local_bh_enable+0x7a/0x80
> > [   11.224199]  up_read+0x1c/0xa0
> > [   11.224446]  do_up_read+0x12/0x20
> > [   11.224713]  irq_work_run_list+0x43/0x70
> > [   11.225030]  irq_work_run+0x26/0x50
> > [   11.225310]  smp_irq_work_interrupt+0x57/0x1f0
> > [   11.225662]  irq_work_interrupt+0xf/0x20
> >
> > since rw_semaphore is released in a different task vs task that locked the sema.
> > It is expected behavior.
> > Fix the warning with up_read_non_owner() and rwsem_release() annotation.
> >
> > Fixes: bae77c5eb5b2 ("bpf: enable stackmap with build_id in nmi context")
> > Signed-off-by: Alexei Starovoitov <ast@...nel.org>
>
> Applied, thanks!

Thanks everyone !