Re: 3.1rc10 null pointer dereferenceideapad_backlight_notify_power

[David Rientjes]

On Wed, 19 Oct 2011, Sam Tygier wrote:

> In kernels 3.1rc9 and 3.1rc10 (from the ubuntu mainline repo) I get a crash
> when disabling and then enabling the screen backlight with the alt+f2 key on a
> lenovo ideapad S12 (intel version). The crash does not occur with 3.0 kernels
> in ubuntu.  I have not tested earlier 3.1 rcs.
> 
> The crash message scrolls to fast to see, it is not writen to a log, and i
> dont see it on a USB serial console (I may be doing something wrong, but I do
> see other messages during boot). I managed to get some photos of the message.
> interesting parts are:
> 
> BUG: unable to handle kernel NULL pointer dereference at 00000008
> IP: [<f807b29e>]  ideapad_backlight_notify_power+0x2e/0x40 [ideapad_laptop]
> *pde = 00000000
> Oops: 0002 [#1] SMP
> 
> call trace functions:
> ideapad_acpi_notify
> acpi_device_notify
> acpi_ev_notify_dispach
> acpi_os_execute_deferred
> process_one_work
> ? acpi_os_wait_events_complete
> ????????? can't read this one
> kthread
> kthread_bind
> kernel_thread_helper
> 
> i put the photos at http://www.hep.manchester.ac.uk/u/sam/pub/ideapad/
> 
> if it would be helpfull, i could try a few more times for sharper photos.
> please let me know if there is any other useful information you need.
> 

Looks light it may be changed via the acpi video driver where ->blight is 
NULL.  Adding Ike and Matthew to the cc.
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