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SubjectRe: [PATCH] cpuidle: Fix panic in CPU off-lining with no idle driver
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@hp.com>
>> Cc: Boris Ostrovsky<boris.ostrovsky@amd.com>
>> ---
>> 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@linux.vnet.ibm.com>
> Tested-by: Srivatsa S. Bhat<srivatsa.bhat@linux.vnet.ibm.com>
>
>
> [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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