On Thu, May 04, 2017 at 09:00:52AM +0000, Li, Fei wrote: > In case of there is no cpuidle devices registered, dev will be null, and > panic will be triggered like below; > In this patch, add checking of dev before usage, like that done in > cpuidle_idle_call. > > Panic without fix: > [ 184.961328] BUG: unable to handle kernel NULL pointer dereference at > (null) > [ 184.961328] IP: cpuidle_use_deepest_state+0x30/0x60 > ... > [ 184.961328] play_idle+0x8d/0x210 > [ 184.961328] ? __schedule+0x359/0x8e0 > [ 184.961328] ? _raw_spin_unlock_irqrestore+0x28/0x50 > [ 184.961328] ? kthread_queue_delayed_work+0x41/0x80 > [ 184.961328] clamp_idle_injection_func+0x64/0x1e0 > > Fixes: bb8313b603eb8 ("cpuidle: Allow enforcing deepest idle state selection") > Signed-off-by: Li, Fei <fei...@intel.com> > Tested-by: Shi, Feng <fengx....@intel.com> > Reviewed-by: Andy Shevchenko <andriy.shevche...@linux.intel.com> > Reviewed-by: Koul, Vinod <vinod.k...@intel.com> > --- > drivers/cpuidle/cpuidle.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c > index 548b90b..2706be7 100644 > --- a/drivers/cpuidle/cpuidle.c > +++ b/drivers/cpuidle/cpuidle.c > @@ -111,7 +111,8 @@ void cpuidle_use_deepest_state(bool enable) > > 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?' > preempt_enable(); > } > > -- > 1.9.1 > > Best Regards, > Fei -- <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook | <http://twitter.com/#!/linaroorg> Twitter | <http://www.linaro.org/linaro-blog/> Blog