linux-kernel - Re: [PATCH 2/2]ACPI: assign different lockdep key for acpi works

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Date:	Mon, 14 Dec 2009 09:08:29 +0800
From:	Shaohua Li <shaohua.li@...el.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"lenb@...nel.org" <lenb@...nel.org>,
	"mingo@...e.hu" <mingo@...e.hu>
Subject: Re: [PATCH 2/2]ACPI: assign different lockdep key for acpi works

On Sat, Dec 12, 2009 at 05:57:16AM +0800, Andrew Morton wrote:
> On Fri, 11 Dec 2009 11:04:58 +0800
> Shaohua Li <shaohua.li@...el.com> wrote:
> 
> > Differentiate works for three different workqueue in ACPI. This fixes
> > a fase alarm from lockdep, as acpi hotplug workqueue waits other
> > workqueues.
> > 
> > http://bugzilla.kernel.org/show_bug.cgi?id=14553
> > 
> > Signed-off-by: Shaohua Li <shaohua.li@...el.com>
> > ---
> >  drivers/acpi/osl.c |   12 +++++++++++-
> >  1 file changed, 11 insertions(+), 1 deletion(-)
> > 
> > Index: linux/drivers/acpi/osl.c
> > ===================================================================
> > --- linux.orig/drivers/acpi/osl.c	2009-12-10 10:40:15.000000000 +0800
> > +++ linux/drivers/acpi/osl.c	2009-12-10 10:43:25.000000000 +0800
> > @@ -729,6 +729,8 @@ static acpi_status __acpi_os_execute(acp
> >  	struct acpi_os_dpc *dpc;
> >  	struct workqueue_struct *queue;
> >  	int ret;
> > +	static struct lock_class_key hp_key, notify_key, acpid_key;
> > +
> >  	ACPI_DEBUG_PRINT((ACPI_DB_EXEC,
> >  			  "Scheduling function [%p(%p)] for deferred execution.\n",
> >  			  function, context));
> > @@ -758,7 +760,15 @@ static acpi_status __acpi_os_execute(acp
> >  	queue = hp ? kacpi_hotplug_wq :
> >  		(type == OSL_NOTIFY_HANDLER ? kacpi_notify_wq : kacpid_wq);
> >  	dpc->wait = hp ? 1 : 0;
> > -	INIT_WORK(&dpc->work, acpi_os_execute_deferred);
> > +	if (queue == kacpi_hotplug_wq)
> > +		INIT_WORK_KEY(&dpc->work, acpi_os_execute_deferred,
> > +				hp_key, "acpi_hp_work");
> > +	else if (queue == kacpi_notify_wq)
> > +		INIT_WORK_KEY(&dpc->work, acpi_os_execute_deferred,
> > +				notify_key, "acpi_notify_work");
> > +	else
> > +		INIT_WORK_KEY(&dpc->work, acpi_os_execute_deferred,
> > +				acpid_key, "acpi_acpid_work");
> >  	ret = queue_work(queue, &dpc->work);
> >  
> >  	if (!ret) {
> 
> Yes, that's a shortcoming in the present INIT_WORK().  However I think
> you can solve this more simply, without introducing INIT_WORK_KEY():
> 
> 	if (queue == kacpi_hotplug_wq)
> 		INIT_WORK(&dpc->work, acpi_os_execute_deferred);
> 	else if (queue == kacpi_notify_wq)
> 		INIT_WORK(&dpc->work, acpi_os_execute_deferred);
> 	else
> 		INIT_WORK(&dpc->work, acpi_os_execute_deferred);
> 
> it looks silly, but I think the compiler will do the right thing with it
> - you'll get a separate lock_class_key at each site.
> 
> Obviously it would need an explanatory comment.
Yes, I tried this way before, it centainly works. I just thought maybe
others need similar API. If I'm over thinking, let's take your way.

Thanks,
Shaohua
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