Re: [PATCH] cpuidle: Fix panic in CPU off-lining with no idle driver

[Toshi Kani]

On 4/3/2012 8:08 AM, Srivatsa S. Bhat wrote:
> On 04/01/2012 09:07 AM, Toshi Kani wrote:
>
> > Fix a NULL pointer dereference panic in cpuidle_play_dead() during
> > CPU off-lining when no cpuidle driver is registered.  A cpuidle
> > driver may be registered at boot-time based on CPU type.  This patch
> > allows an off-lined CPU to enter HLT-based idle in this condition.
> >
> > Signed-off-by: Toshi Kani<toshi.kani@xxxxxx>
> > Cc: Boris Ostrovsky<boris.ostrovsky@xxxxxxx>
> > ---
> >   drivers/cpuidle/cpuidle.c |    5 ++++-
> >   1 files changed, 4 insertions(+), 1 deletions(-)
> >
> > diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
> > index 87411ce..2f0083a 100644
> > --- a/drivers/cpuidle/cpuidle.c
> > +++ b/drivers/cpuidle/cpuidle.c
> > @@ -74,7 +74,7 @@ static cpuidle_enter_t cpuidle_enter_ops;
> >   /**
> >    * cpuidle_play_dead - cpu off-lining
> >    *
> > - * Only returns in case of an error
> > + * Returns in case of an error or no driver
> >    */
> >   int cpuidle_play_dead(void)
> >   {
> > @@ -83,6 +83,9 @@ int cpuidle_play_dead(void)
> >   	int i, dead_state = -1;
> >   	int power_usage = -1;
> >
> > +	if (!drv)
> > +		return -ENODEV;
> > +
> >   	/* Find lowest-power state that supports long-term idle */
> >   	for (i = CPUIDLE_DRIVER_STATE_START; i<  drv->state_count; i++) {
> >   		struct cpuidle_state *s =&drv->states[i];
>
>
> Reviewed-by: Srivatsa S. Bhat<srivatsa.bhat@xxxxxxxxxxxxxxxxxx>
> Tested-by: Srivatsa S. Bhat<srivatsa.bhat@xxxxxxxxxxxxxxxxxx>
>
>
> [The machine I tested on did support mwait. So, to disable mwait and ensure
> that no idle driver is registered, I applied my fix for "idle=" parameters
> (https://lkml.org/lkml/2012/4/3/158) and then passed idle=halt in the kernel
> command line. Then the machine crashed during CPU offline. Then I tried your
> patch and it fixed the issue.]

Great!  Thanks a lot Srivatsa for reviewing and testing!
-Toshi

> Regards,
> Srivatsa S. Bhat
> IBM Linux Technology Center

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