From: Tejun Heo <tj@kernel.org>
To: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Bart Van Assche <bvanassche@acm.org>,
syzbot <syzbot+831661966588c802aae9@syzkaller.appspotmail.com>,
jgg@ziepe.ca, linux-kernel@vger.kernel.org,
linux-rdma@vger.kernel.org, syzkaller-bugs@googlegroups.com,
Lai Jiangshan <jiangshanlai@gmail.com>
Subject: Re: [syzbot] possible deadlock in worker_thread
Date: Mon, 14 Feb 2022 07:34:42 -1000 [thread overview]
Message-ID: <YgqSsuSN5C7StvKx@slm.duckdns.org> (raw)
In-Reply-To: <8ebd003c-f748-69b4-3a4f-fb80a3f39d36@I-love.SAKURA.ne.jp>
Hello,
On Mon, Feb 14, 2022 at 10:36:57PM +0900, Tetsuo Handa wrote:
> OK. Then, I propose below patch. If you are OK with this approach, I can
> keep this via my tree as a linux-next only experimental patch for one or
> two weeks, in order to see if someone complains.
I don't mind you testing that way but this and would much prefer this and
related changes in the wq tree.
> +static void warn_if_flushing_global_workqueue(struct workqueue_struct *wq)
> +{
> +#ifdef CONFIG_PROVE_LOCKING
> + static DEFINE_RATELIMIT_STATE(flush_warn_rs, 600 * HZ, 1);
> + const char *name;
> +
> + if (wq == system_wq)
> + name = "system_wq";
> + else if (wq == system_highpri_wq)
> + name = "system_highpri_wq";
> + else if (wq == system_long_wq)
> + name = "system_long_wq";
> + else if (wq == system_unbound_wq)
> + name = "system_unbound_wq";
> + else if (wq == system_freezable_wq)
> + name = "system_freezable_wq";
> + else if (wq == system_power_efficient_wq)
> + name = "system_power_efficient_wq";
> + else if (wq == system_freezable_power_efficient_wq)
> + name = "system_freezable_power_efficient_wq";
> + else
> + return;
> + ratelimit_set_flags(&flush_warn_rs, RATELIMIT_MSG_ON_RELEASE);
> + if (!__ratelimit(&flush_warn_rs))
> + return;
> + pr_warn("Since system-wide WQ is shared, flushing system-wide WQ can introduce unexpected locking dependency. Please replace %s usage in your code with your local WQ.\n",
> + name);
> + dump_stack();
> +#endif
Instead of doing the above, please add a wq flag to mark system wqs and
trigger the warning that way and I'd leave it regardless of PROVE_LOCKING.
Thanks.
--
tejun
next prev parent reply other threads:[~2022-02-14 17:34 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-10 19:27 [syzbot] possible deadlock in worker_thread syzbot
2022-02-11 18:59 ` Bart Van Assche
2022-02-12 5:31 ` Tetsuo Handa
2022-02-12 16:37 ` Bart Van Assche
2022-02-12 17:14 ` Tetsuo Handa
2022-02-13 15:33 ` Leon Romanovsky
2022-02-13 23:06 ` Bart Van Assche
2022-02-14 1:08 ` Tetsuo Handa
2022-02-14 3:44 ` Tejun Heo
2022-02-14 13:36 ` Tetsuo Handa
2022-02-14 17:34 ` Tejun Heo [this message]
2022-02-15 10:26 ` Tetsuo Handa
2022-02-15 10:43 ` Haakon Bugge
2022-02-15 12:48 ` Tetsuo Handa
2022-02-15 17:05 ` Bart Van Assche
2022-02-15 22:05 ` Tetsuo Handa
2022-02-22 18:26 ` Tejun Heo
2022-02-17 11:22 ` [PATCH v2] workqueue: Warn flush attempt using system-wide workqueues Tetsuo Handa
2022-02-22 18:36 ` Tejun Heo
[not found] ` <CGME20220223212048eucas1p1fab5e35ff398eff57808a8f1125dd15f@eucas1p1.samsung.com>
2022-02-23 21:20 ` Marek Szyprowski
2022-02-23 21:35 ` Tejun Heo
2022-02-23 22:06 ` Tetsuo Handa
2022-02-17 12:27 ` [syzbot] possible deadlock in worker_thread Fabio M. De Francesco
2022-02-22 18:30 ` Tejun Heo
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