linux-kernel - Re: [RFC PATCH 0/3] sysfs: allow suicide

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Date:	Thu, 26 Mar 2009 15:56:09 +0100
From:	Cornelia Huck <cornelia.huck@...ibm.com>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Tejun Heo <htejun@...il.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Alex Chiang <achiang@...com>, <greg@...ah.com>,
	<kay.sievers@...y.org>, <rusty@...tcorp.com.au>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 0/3] sysfs: allow suicide

On Thu, 26 Mar 2009 10:21:23 -0400 (EDT),
Alan Stern <stern@...land.harvard.edu> wrote:

> The idea is that this would come in useful both for suicidal sysfs 
> attributes and for hot-unplug events detected by an interrupt handler.

Yes; the ccw bus uses it's own workqueue, so it doesn't need
device_schedule_callback() to commit suicide. I guess other busses
could do the same.

> 
> But there's something I'm not clear on.  If hot-unplug events are
> detected by an interrupt handler, then what about hot-plug events?  
> Wouldn't they be detected by the same interrupt handler?  Obviously you
> can't register new devices in interrupt context, so there must be a
> workqueue or kernel thread involved somewhere.  Shouldn't the two types
> of events be managed by the same workqueue/thread?

They should, you want to serialize plug/unplug. You'll even want to use
the same queue for plug/unplug not detected in interrupt context.

The next question is how granular those workqueues should be. Per
subsystem? Per bus? Something else?
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