linux-kernel - Re: [PATCH] cpuidle: coupled: Enable interrupts when early returning on invalid driver

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Date:	Thu, 24 Jul 2014 11:46:31 +0200
From:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
To:	Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, Colin Cross <ccross@...roid.com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	stable@...r.kernel.org
Subject: Re: [PATCH] cpuidle: coupled: Enable interrupts when early returning
 on invalid driver

On czw, 2014-07-24 at 11:35 +0200, Daniel Lezcano wrote:
> On 07/24/2014 11:26 AM, Krzysztof Kozlowski wrote:
> > cpuidle_enter_state is expected to return with interrupts enabled.
> > However cpuidle_enter_state_coupled returned with interrupts disabled if
> > the cpuidle driver was registered without mask of coupled cpus.
> 
> Hi Krzysztof,
> 
> may be your patch is right but I would like to clarify one thing. This 
> is the cpuidle driver for exynos. AFAICT, the coupled states shouldn't 
> be enabled for this driver, so how did you face this issue ?

I faced this on cpuidle drivers on both Exynos and MSM. But these were
not mainline cpuidle drivers.

Best regards,
Krzysztof

> > This could be observed as a warning:
> > [    1.613132] ------------[ cut here ]------------
> > [    1.613244] WARNING: CPU: 0 PID: 0 at kernel/sched/idle.c:175 cpu_idle_loop+0x2dc/0x6d0()
> > [    1.620268] Modules linked in:
> > [    1.623311] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.16.0-rc4-00102-g7669ccdbf8af-dirty #81
> > [    1.623619] dwmmc_exynos 12510000.mshc: 1 slots initialized
> > [    1.624890] logger: created 256K log 'log_main'
> > [    1.625483] logger: created 256K log 'log_events'
> > [    1.626084] logger: created 256K log 'log_radio'
> > [    1.626699] logger: created 256K log 'log_system'
> > [    1.655960] [<c00167cc>] (unwind_backtrace) from [<c0012c28>] (show_stack+0x10/0x14)
> > [    1.663679] [<c0012c28>] (show_stack) from [<c050ab00>] (dump_stack+0x70/0xbc)
> > [    1.670883] [<c050ab00>] (dump_stack) from [<c0023ac8>] (warn_slowpath_common+0x68/0x8c)
> > [    1.678954] [<c0023ac8>] (warn_slowpath_common) from [<c0023b08>] (warn_slowpath_null+0x1c/0x24)
> > [    1.687720] [<c0023b08>] (warn_slowpath_null) from [<c006ddd4>] (cpu_idle_loop+0x2dc/0x6d0)
> > [    1.696052] [<c006ddd4>] (cpu_idle_loop) from [<c006e1d4>] (cpupri_find+0x0/0xd4)
> > [    1.703518] [<c006e1d4>] (cpupri_find) from [<c07cdd14>] (processor_id+0x0/0x2c)
> > [    1.710917] ---[ end trace a85327313857296e ]---
> >
> > Enable the interrupts also when early returning from
> > cpuidle_enter_state_coupled due to invalid coupled configuration.
> >
> > Signed-off-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>
> > Fixes: 4126c0197bc8 ("cpuidle: add support for states that affect multiple cpus")
> > Cc: <stable@...r.kernel.org>
> > ---
> >   drivers/cpuidle/coupled.c | 4 +++-
> >   1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/cpuidle/coupled.c b/drivers/cpuidle/coupled.c
> > index 73fe2f8d7f96..2b57c267e855 100644
> > --- a/drivers/cpuidle/coupled.c
> > +++ b/drivers/cpuidle/coupled.c
> > @@ -463,8 +463,10 @@ int cpuidle_enter_state_coupled(struct cpuidle_device *dev,
> >   	struct cpuidle_coupled *coupled = dev->coupled;
> >   	int w;
> >
> > -	if (!coupled)
> > +	if (!coupled) {
> > +		local_irq_enable();
> >   		return -EINVAL;
> > +	}
> >
> >   	while (coupled->prevent) {
> >   		cpuidle_coupled_clear_pokes(dev->cpu);
> >
> 
> 

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