linux-kernel - RE: [PATCH V3] cpuidle: check dev before usage in cpuidle_use_deepest

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Date:   Fri, 5 May 2017 01:53:24 +0000
From:   "Li, Fei" <fei.li@...el.com>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
CC:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        "Shi, FengX" <fengx.shi@...el.com>,
        "rjw@...ysocki.net" <rjw@...ysocki.net>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Koul, Vinod" <vinod.koul@...el.com>
Subject: RE: [PATCH V3] cpuidle: check dev before usage in
 cpuidle_use_deepest_state

On Thursday, May 4, 2017 6:16 PM Daniel Lezcano wrote:
> >
> >     preempt_disable();
> >     dev = cpuidle_get_device();
> > -   dev->use_deepest_state = enable;
> > +   if (dev)
> > +       dev->use_deepest_state = enable;
> 
> 
> This change is acceptable as a hot fix but the question is 'why is this
> function called if there is no cpuidle driver registered?'

It's called as below:
clamp_idle_injection_func
	-> play_idle
		-> cpuidle_use_deepest_state
In play_idle, if no cpuidle driver registered, cpu_idle_poll can be called.
It seems to go too far if not calling play_idle in case of no cpuidle driver
registered.
At present no other suitable and simple fix seen.

> 
> >     preempt_enable();
> >  }
> >
> > --
> > 1.9.1
> >
> > Best Regards,
> > Fei
> 
> --
> 
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Best Regards,
Fei