linux-kernel - Re: [PATCH 3/3] serial: 8250: Add a wakeup

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Date:	Fri, 20 Jan 2012 01:03:34 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	paulmck@...ux.vnet.ibm.com
Cc:	Simon Glass <sjg@...omium.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	LKML <linux-kernel@...r.kernel.org>,
	"Greg Kroah-Hartman" <gregkh@...e.de>, linux-serial@...r.kernel.org
Subject: Re: [PATCH 3/3] serial: 8250: Add a wakeup_capable module param

On Thursday, January 19, 2012, Paul E. McKenney wrote:
> On Thu, Jan 19, 2012 at 01:02:58AM +0100, Rafael J. Wysocki wrote:
> > On Wednesday, January 18, 2012, Paul E. McKenney wrote:
> > > On Wed, Jan 18, 2012 at 02:15:59PM -0800, Simon Glass wrote:
[...] 
> > Yes, you can, but then I'd say it's not necessary for user space to
> > be able to carry that out in a tight loop.  So, it seems, alternatively,
> > we could make that loop a bit less tight, e.g. by adding an arbitrary
> > sleep to the user space interface for the "disable" case.
> 
> Good point, that would work just as well and be simpler.

Thanks for the confirmation! :-)

By the way, I wonder, would it help to add synchronize_rcu() to
wakeup_source_add() too?  Then, even if device_wakeup_enable() and
device_wakeup_disable() are executed in a tight loop for the same
device, the list_add/list_del operations will always happen in
different RCU cycles (or at least it seems so).

Thanks,
Rafael
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