From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
To: 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,
Tejun Heo <tj@kernel.org>, Lai Jiangshan <jiangshanlai@gmail.com>
Subject: Re: [syzbot] possible deadlock in worker_thread
Date: Sun, 13 Feb 2022 02:14:09 +0900 [thread overview]
Message-ID: <309c86b7-2a4c-1332-585f-7bcd59cfd762@I-love.SAKURA.ne.jp> (raw)
In-Reply-To: <71d6f14e-46af-cc5a-bc70-af1cdc6de8d5@acm.org>
On 2022/02/13 1:37, Bart Van Assche wrote:
> On 2/11/22 21:31, Tetsuo Handa wrote:
>> But this report might be suggesting us that we should consider
>> deprecating (and eventually getting rid of) system-wide workqueues
>> (declared in include/linux/workqueue.h), for since flush_workqueue()
>> synchronously waits for completion, sharing system-wide workqueues
>> among multiple modules can generate unexpected locking dependency
>> chain (like this report).
>
> I do not agree with deprecating system-wide workqueues. I think that
> all flush_workqueue(system_long_wq) calls should be reviewed since
> these are deadlock-prone.
>
> Thanks,
>
> Bart.
The loop module is not using flush_workqueue(system_long_wq) call; it only
scheduled a work via system_long_wq which will call flush_workqueue() (of
a local workqueue) from drain_workqueue() from destroy_workqueue() from
work function.
How can reviewing all flush_workqueue(system_long_wq) calls help?
next prev parent reply other threads:[~2022-02-12 17:14 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 [this message]
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
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=309c86b7-2a4c-1332-585f-7bcd59cfd762@I-love.SAKURA.ne.jp \
--to=penguin-kernel@i-love.sakura.ne.jp \
--cc=bvanassche@acm.org \
--cc=jgg@ziepe.ca \
--cc=jiangshanlai@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-rdma@vger.kernel.org \
--cc=syzbot+831661966588c802aae9@syzkaller.appspotmail.com \
--cc=syzkaller-bugs@googlegroups.com \
--cc=tj@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).