From: Alan Stern <stern@rowland.harvard.edu>
To: Oliver Neukum <oneukum@suse.com>
Cc: Tejun Heo <tj@kernel.org>,
Kernel development list <linux-kernel@vger.kernel.org>,
USB list <linux-usb@vger.kernel.org>
Subject: Re: [RFC] deadlock with flush_work() in UAS
Date: Mon, 1 Jul 2019 10:20:36 -0400 (EDT) [thread overview]
Message-ID: <Pine.LNX.4.44L0.1907011017130.1536-100000@iolanthe.rowland.org> (raw)
In-Reply-To: <1561978947.10014.12.camel@suse.com>
On Mon, 1 Jul 2019, Oliver Neukum wrote:
> Am Mittwoch, den 26.06.2019, 10:38 -0400 schrieb Alan Stern:
> > On Wed, 26 Jun 2019, Oliver Neukum wrote:
> >
> > > Am Montag, den 24.06.2019, 10:22 -0400 schrieb Alan Stern:
> > > > But that pattern makes no sense; a driver would never use it. The
> > > > driver would just do the reset itself.
> > >
> > > Correct. But UAS and storage themselves still need to use
> > > WQ_MEM_RECLAIM for their workqueues, don't they?
> >
> > Perhaps so for uas. usb-storage uses a work queue only for scanning
> > targets, which doesn't interfere with the block I/O pathway.
>
> Are you sure? What about hub_tt_work?
Technically speaking, hub_tt_work is used by the hub driver, not by
usb-storage. :-)
> As far as I can tell, hub_quiesce
> will flush it, hence it is used in error handling.
Yes, it needs to use a work queue with WQ_MEM_RECLAIM set.
Unfortunately, I don't think we can use hub_wq for this purpose (we
could end up with a work item waiting for another work item later on in
the same queue, not good).
Alan Stern
prev parent reply other threads:[~2019-07-01 14:20 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1560871774.3184.16.camel@suse.com>
2019-06-18 15:59 ` [RFC] deadlock with flush_work() in UAS Alan Stern
2019-06-20 14:10 ` Tejun Heo
2019-06-24 8:56 ` Oliver Neukum
2019-06-24 14:22 ` Alan Stern
2019-06-26 8:10 ` Oliver Neukum
2019-06-26 14:38 ` Alan Stern
2019-07-01 11:02 ` Oliver Neukum
2019-07-01 14:20 ` Alan Stern [this message]
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