linux-kernel - Re: Freezable workqueue blocks non-freezable workqueue during the system resume process

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Date:	Thu, 25 Feb 2016 17:01:12 -0500
From:	Tejun Heo <tj@...nel.org>
To:	Peter Chen <hzpeterchen@...il.com>
Cc:	Alan Stern <stern@...land.harvard.edu>, florian@...kler.org,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	usb-storage@...ts.one-eyed-alien.net
Subject: Re: Freezable workqueue blocks non-freezable workqueue during the
 system resume process

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?

Thanks.

-- 
tejun