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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