linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Tejun Heo <tj@kernel.org>
To: Peter Chen <hzpeterchen@gmail.com>
Cc: Alan Stern <stern@rowland.harvard.edu>,
	florian@mickler.org, linux-usb@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	usb-storage@lists.one-eyed-alien.net, Jan Kara <jack@suse.com>
Subject: Re: Freezable workqueue blocks non-freezable workqueue during the system resume process
Date: Wed, 2 Mar 2016 11:00:58 -0500	[thread overview]
Message-ID: <20160302160058.GA29826@mtj.duckdns.org> (raw)
In-Reply-To: <20160226061920.GA17288@shlinux2.ap.freescale.net>

Hello,

(cc'ing Jan)

On Fri, Feb 26, 2016 at 02:19:20PM +0800, Peter Chen wrote:
> On Thu, Feb 25, 2016 at 05:01:12PM -0500, Tejun Heo wrote:
> > Hello, Peter.
> > 
> > On Wed, Feb 24, 2016 at 03:24:30PM +0800, Peter Chen wrote:
> > > > You might want to complain to the block-layer people about this.  I 
> > > > don't know if anything can be done to fix it.
> > > > 
> > > > Or maybe flush_work and flush_delayed_work can be changed to avoid 
> > > > blocking if the workqueue is frozen.  Tejun?
> > > > 
> > > 
> > > I have a patch to show the root cause of this issue.
> > > 
> > > http://www.spinics.net/lists/linux-usb/msg136815.html
> > 
> > I don't get it.  Why would it deadlock?  Shouldn't things get rolling
> > once the workqueues are thawed?
> 
> The workqueue writeback can't be thawed due to driver's resume
> (dpm_complete) is lock nested, and can't be finished.

Ugh... that's nasty.  I wonder whether the right thing to do is making
writeback workers non-freezable.  IOs are supposed to be blocked from
lower layer anyway.  Jan, what do you think?

Thanks.

-- 
tejun

  reply	other threads:[~2016-03-02 16:01 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-02-23  3:20 Freezable workqueue blocks non-freezable workqueue during the system resume process Peter Chen
2016-02-23  9:47 ` Peter Chen
2016-02-23 15:34 ` Alan Stern
2016-02-24  7:24   ` Peter Chen
2016-02-25 22:01     ` Tejun Heo
2016-02-26  6:19       ` Peter Chen
2016-03-02 16:00         ` Tejun Heo [this message]
2016-03-03  9:33           ` Jan Kara
2016-03-11 17:56             ` Tejun Heo
2016-03-14  7:22               ` Jan Kara
2016-03-14 14:37                 ` Alan Stern
2016-03-15  9:25                   ` Jan Kara
2016-03-16 15:00                     ` 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=20160302160058.GA29826@mtj.duckdns.org \
    --to=tj@kernel.org \
    --cc=florian@mickler.org \
    --cc=hzpeterchen@gmail.com \
    --cc=jack@suse.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-usb@vger.kernel.org \
    --cc=stern@rowland.harvard.edu \
    --cc=usb-storage@lists.one-eyed-alien.net \
    /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).