linux-kernel - Re: [PATCH RFC] acpi: Fix unprotected smp_processor_id() in acpi_processor_cst_has

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Message-ID: <20120228133013.GE2465@linux.vnet.ibm.com>
Date:	Tue, 28 Feb 2012 05:30:13 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Yong Zhang <yong.zhang0@...il.com>
Cc:	deepthi@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org,
	lenb@...nel.org, linux-acpi@...r.kernel.org
Subject: Re: [PATCH RFC] acpi: Fix unprotected smp_processor_id() in
 acpi_processor_cst_has_changed()

On Tue, Feb 28, 2012 at 03:19:43PM +0800, Yong Zhang wrote:
> On Thu, Feb 23, 2012 at 12:58:05PM -0800, Paul E. McKenney wrote:
> > The acpi_processor_cst_has_changed() function is invoked from a
> > CPU_ONLINE or CPU_DEAD function, which might well execute on CPU 0
> > even though the CPU being hotplugged is some other CPU.  In addition,
> > acpi_processor_cst_has_changed() invokes smp_processor_id() without
> > protection, resulting in splats when onlining CPUs.
> > 
> > This commit therefore changes the smp_processor_id() to pr->id, as is
> > used elsewhere in the code, for example, in acpi_processor_add().
> > 
> > This works for me, but I don't claim to understand ACPI.
> > 
> > Signed-off-by: Paul E. McKenney <paul.mckenney@...aro.org>
> 
> Got the same warning.
> And the patch works on my side.
> 
> Tested-by: Yong Zhang <yong.zhang0@...il.com>

Thank you, I have added your Tested-by (and Srivatsa's Reviewed-by,
for that matter).

Any takers for this, or should I just push it up the -tip tree?

							Thanx, Paul

> > diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
> > index 0e8e2de..9e57b06 100644
> > --- a/drivers/acpi/processor_idle.c
> > +++ b/drivers/acpi/processor_idle.c
> > @@ -1159,8 +1159,7 @@ int acpi_processor_cst_has_changed(struct acpi_processor *pr)
> >  	 * to make the code that updates C-States be called once.
> >  	 */
> >  
> > -	if (smp_processor_id() == 0 &&
> > -			cpuidle_get_driver() == &acpi_idle_driver) {
> > +	if (pr->id == 0 && cpuidle_get_driver() == &acpi_idle_driver) {
> >  
> >  		cpuidle_pause_and_lock();
> >  		/* Protect against cpu-hotplug */
> > 
> > --
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> 
> -- 
> Only stand for myself
> 

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