From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Yonghong Song <yhs@fb.com>
Cc: bpf@vger.kernel.org, Alexei Starovoitov <ast@fb.com>,
Daniel Borkmann <daniel@iogearbox.net>,
kernel-team@fb.com, Song Liu <songliubraving@fb.com>
Subject: Re: [PATCH bpf v3 1/2] bpf: Fix deadlock with rq_lock in bpf_send_signal()
Date: Thu, 5 Mar 2020 14:14:58 -0800 [thread overview]
Message-ID: <20200305221456.mh72lwvp55l32rfm@ast-mbp> (raw)
In-Reply-To: <20200304191104.2796501-1-yhs@fb.com>
On Wed, Mar 04, 2020 at 11:11:04AM -0800, Yonghong Song wrote:
>
> - if (in_nmi()) {
> + /* Delay sending signal if irq is disabled. Otherwise,
> + * we risk deadlock with rq_lock.
> + */
This comment read in isolation is confusing. It's not clear how irq
has anything to do with rq_lock and why deadlock is possible.
But commit log has very nice summary,
so I've just deleted that comment and applied to bpf tree.
The patch 2 did reproduce the lockdep splat for me. Which was great.
Running test_progs few times before and after I noticed that older
send_signal tests are flaky and fail from time to time.
It's unrelated to this patch, but please take a look.
next prev parent reply other threads:[~2020-03-05 22:15 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-04 19:11 [PATCH bpf v3 0/2] bpf: Fix deadlock with rq_lock in bpf_send_signal() Yonghong Song
2020-03-04 19:11 ` [PATCH bpf v3 1/2] " Yonghong Song
2020-03-05 22:14 ` Alexei Starovoitov [this message]
2020-03-04 19:11 ` [PATCH bpf v3 2/2] selftests/bpf: add send_signal_sched_switch test Yonghong Song
2020-03-04 20:21 ` Andrii Nakryiko
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