From: Tejun Heo <tj@kernel.org>
To: "Fabio M. De Francesco" <fmdefrancesco@gmail.com>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
syzkaller-bugs@googlegroups.com,
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,
Lai Jiangshan <jiangshanlai@gmail.com>
Subject: Re: [syzbot] possible deadlock in worker_thread
Date: Tue, 22 Feb 2022 08:30:22 -1000 [thread overview]
Message-ID: <YhUrvpwkH07Yr2sW@slm.duckdns.org> (raw)
In-Reply-To: <4168398.ejJDZkT8p0@leap>
Hello,
On Thu, Feb 17, 2022 at 01:27:08PM +0100, Fabio M. De Francesco wrote:
> Just to think and understand... what if the system-wide WQ were allocated as unbound
> ordered (i.e., as in alloc_ordered_workqueue()) with "max_active" of one?
>
> 1) Would it solve the locks dependency problem?
It'll actually make deadlocks a lot more prevalent. Some work items take
more than one work to complete (e.g. flushing another work directly or
waiting for something which must be completed by something else which may
involve a system work item) and system wq's max active must be high enough
that all those chains taking place at the same time should require fewer
number of work items than max_active.
> 2) Would it introduce performance penalties (bottlenecks)?
I'd be surprised it wouldn't cause at least notcieable latency increases for
some workloads.
Thanks.
--
tejun
prev parent reply other threads:[~2022-02-22 18:30 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
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 [this message]
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=YhUrvpwkH07Yr2sW@slm.duckdns.org \
--to=tj@kernel.org \
--cc=bvanassche@acm.org \
--cc=fmdefrancesco@gmail.com \
--cc=jgg@ziepe.ca \
--cc=jiangshanlai@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-rdma@vger.kernel.org \
--cc=penguin-kernel@i-love.sakura.ne.jp \
--cc=syzbot+831661966588c802aae9@syzkaller.appspotmail.com \
--cc=syzkaller-bugs@googlegroups.com \
/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).