From: Peter Zijlstra <peterz@infradead.org>
To: Song Liu <songliubraving@fb.com>
Cc: Networking <netdev@vger.kernel.org>,
Kernel Team <Kernel-team@fb.com>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>
Subject: Re: [PATCH bpf-next 1/2] bpf: enable stackmap with build_id in nmi context
Date: Wed, 2 May 2018 19:30:27 +0200 [thread overview]
Message-ID: <20180502173027.GM12180@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <30F32ACF-5155-459B-BD47-5060CCA52788@fb.com>
On Wed, May 02, 2018 at 04:48:32PM +0000, Song Liu wrote:
> > It's broken though, I've bet you've never actually ran this with lockdep
> > enabled for example.
>
> I am not following here. I just run the new selftest with CONFIG_LOCKDEP on,
> and got no warning for this.
Weird, I would be expecting complaints about releasing an unheld lock.
nmi_enter(),nmi_exit() have lockdep_off(),lockdep_on() resp. Which means
that the down_trylock() will not be recorded. The up, which is done from
IRQ context, will not be so supressed and should hit
print_unlock_imbalance_bug().
> > Also, you set work->sem before you do trylock, if the trylock fails you
> > return early and keep work->sem set, which will thereafter always result
> > in irq_work_busy.
>
> work->sem was set after down_read_trylock(). I guess you misread the patch?
Argh, yes indeed. Sorry.
next prev parent reply other threads:[~2018-05-02 17:30 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-02 0:02 [PATCH bpf-next 1/2] bpf: enable stackmap with build_id in nmi context Song Liu
2018-05-02 0:02 ` [PATCH bpf-next 2/2] bpf: add selftest for stackmap with build_id in NMI context Song Liu
2018-05-02 3:34 ` [RFC PATCH] bpf: __pcpu_scope_irq_work can be static kbuild test robot
2018-05-02 3:34 ` [PATCH bpf-next 1/2] bpf: enable stackmap with build_id in nmi context kbuild test robot
2018-05-02 9:21 ` Peter Zijlstra
2018-05-02 16:48 ` Song Liu
2018-05-02 17:30 ` Peter Zijlstra [this message]
2018-05-02 17:57 ` Song Liu
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