linux-kernel - Re: 2.6.21-rc suspend regression: sysfs deadlock

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Message-ID: <Pine.LNX.4.64.0703151219540.12584@blonde.wat.veritas.com>
Date:	Thu, 15 Mar 2007 12:31:50 +0000 (GMT)
From:	Hugh Dickins <hugh@...itas.com>
To:	Cornelia Huck <cornelia.huck@...ibm.com>
cc:	Alan Stern <stern@...land.harvard.edu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Oliver Neukum <oneukum@...e.de>,
	Maneesh Soni <maneesh@...ibm.com>, gregkh@...e.de,
	Richard Purdie <rpurdie@...ys.net>,
	James Bottomley <James.Bottomley@...elEye.com>,
	Kernel development list <linux-kernel@...r.kernel.org>
Subject: Re: 2.6.21-rc suspend regression: sysfs deadlock

On Thu, 15 Mar 2007, Cornelia Huck wrote:
> On Wed, 14 Mar 2007 15:23:10 -0400 (EDT),
> Alan Stern <stern@...land.harvard.edu> wrote:
> > 
> > sysfs_work_struct is too generic; other parts of sysfs might also want to
> > use workqueues for different purposes.
> 
> > I don't like calling it "delayed"-anything, because the operations aren't
> > necessarily delayed!  On an SMP system they might even execute before the
> > sysfs_access_in_other_task() call returns.  (Although the two examples we
> > have so far can't do that because of lock contention.)
> 
> Sure. But then you shouldn't refer to "delay" in the comments for the
> functions as well :)
> 
> > The major feature added here is that the work takes place in a different 
> > task's context, not that it is delayed.  Hence the choice of names.
> 
> Hm. Perhaps device_schedule_access()?

It's really none of my business, I'm merely the reporter the
deadlock being fixed, and I don't know my way around sysfs at all ...

... but I have to say I share your discomfort with Alan's
"sysfs_access_in_other_task" naming, it sounded very weird to me.

Quite apart from this mysterious "other task", I don't understand
"access" either.

Perhaps "defer" would best capture the idea of another-task and
maybe-delay?  sysfs_defer_work(), struct sysfs_deferred_work?

Hugh
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