BUG: Null pointer dereference on booting TC2 with vexpress_defconfig

[Christoffer Dall]

On 18 February 2014 03:04, Sudeep Holla <Sudeep.Holla at arm.com> wrote:
> On 17/02/14 22:39, Christoffer Dall wrote:
>> Booting my TC2 using 3.14-rc3 and vexpress_defconfig causes a NULL
>> pointer dereference in schedule_work_on.
>>
>> A quick look at the trace indicates that schedule_work() is called
>> before system_wq is initialized.
>>
>> Further, a bisect seems to indicate that this call path is triggered by
>> the changes in this merge commit of Theodore T'so's random_for_linus
>> tag:
>> 0891ad829d2a0501053703df66029e843e3b8365
>>
>> (However, my bisect may not be 100% correct, as some of the commits
>> between 3.13 and 3.12 don't boot the TC2 with vexpress_defconfig,
>> specifically the ones after f9300eaaac1ca300083ad41937923a90cc3a2394,
>> which causes boot to halt after "ARM CCI driver probed").
>>
> Yes that requires some changes in defconfig to continue to work across
> these changes(mainly have all these new configs disabled)
>

So vexpress_defconfig is known to not work on TC2?

>> Disabling CONFIG_ARCH_VEXPRESS_TC2_PM avoids the issue.
>>
> Are you just disabling this or even CONFIG_MCPM ? Are the secondaries cpus
> coming up ?
>

Disabling CONFIG_ARCH_VEXPRESS_TC2_PM allows the system to boot, but
only with one CPU.

Disabling CONFIG_MCPM allows SMP boot as well.

>> I'm not familiar enough with any of these code paths to quicly identify
>> what the issue could be.  Apologies if I missed a previous post about
>> this issue (I couldn't find anything but would be surprised if I'm the
>> only one doing vexpress_defconfig on a TC2).
>>
> I just tried and it works fine. If CONFIG_MCPM and CONFIG_ARCH_VEXPRESS_TC2_PM,
> it requires some changes in board configurations(for bootmon), I assume you have
> done those changes.
>

What works fine? With both configs enabled?

I didn't change anything on the boot monitor side.  Can you give me a
pointer to the specifics?  Was there an announcement about this
somewhere that I failed to locate?

Thanks for your help!

-Christoffer