Re: 3.14.3-rt5: at91: Crash early at boot

[Christian Jann <Christian.Jann@elektrobit.com>]

Alexandre Belloni <alexandre.belloni <at> free-electrons.com> writes:

Hi all,

> 
> Hi Maxime,
> 
> On 16/03/2015 at 19:19:00 +0100, Maxime Ripard wrote :
> > Hi,
> > 
> > On Tue, Feb 17, 2015 at 09:38:59AM +0100, Sebastian Andrzej Siewior wrote:
> > > * Maxime Ripard | 2014-06-13 16:25:06 [+0200]:
> > > 
> > > >Preemptible hierarchical RCU implementation.
> > > >NR_IRQS:16 nr_irqs:16 16
> > > >Unable to handle kernel NULL pointer dereference at virtual address
00000000
> > > >pgd = c0004000
> > > >[00000000] *pgd=00000000
> > > >Internal error: Oops: 5 [#1] PREEMPT ARM
> > > >Modules linked in:
> > > >CPU: 0 PID: 0 Comm: swapper Not tainted 3.14.3-rt4+ #11
> > > >task: c05ecb28 ti: c05e2000 task.ti: c05e2000
> > > >PC is at wake_up_process+0x8/0x40
> > > >LR is at kthread_create_on_node+0xb0/0x178
> > > …
> > > >Do you know what could be the cause of this, or is this any known issue?
> > > 
> > > No. This is very early in the boot process. I upgrade the at91's timer
> > > patches but have no HW to actually check if this is still working.
> > 
> > Do you have a link to these patches?
> > 
> The issue has been solved at emtrion but I think the patches were not
> sent yet. The issue is that threading the timer IRQs leads to a crash
> because kthreadd is not started yet.
> 


Are there any updates concerning the patches or does anybody have some more
information on how the problem was resolved on the Atmel controller?

I'm encountering the same problem on a Tegra K1 processor with a
3.10.61-rt65 kernel and I'm unsure what's the best way to fix it.

Unable to handle kernel NULL pointer dereference at virtual address 00000000
[<c0072c80>] (wake_up_process+0x10/0x4c) from [<c005ff20>]
(kthread_create_on_node+0x84/0xec)
[<c005ff20>] (kthread_create_on_node+0x84/0xec) from [<c00bb67c>]
(__setup_irq+0x29c/0x4cc)
[<c00bb67c>] (__setup_irq+0x29c/0x4cc) from [<c00bb8f4>] (setup_irq+0x48/0x90)
[<c00bb8f4>] (setup_irq+0x48/0x90) from [<c06d9f38>]
(tegra3_register_wake_timer+0x28/0x64)
[<c06d9f38>] (tegra3_register_wake_timer+0x28/0x64) from [<c0cea0fc>]
(tegra_init_timer+0x23c/0x36c)
[<c0cea0fc>] (tegra_init_timer+0x23c/0x36c) from [<c0ce9a88>]
(clocksource_of_init+0x34/0x58)
[<c0ce9a88>] (clocksource_of_init+0x34/0x58) from [<c0cba2b4>]
(time_init+0x2c/0x38)
[<c0cba2b4>] (time_init+0x2c/0x38) from [<c0cb79ac>] (start_kernel+0x234/0x370)
Kernel panic - not syncing: Attempted to kill the idle task!

The problem is time_init() gets executed far before rest_init() where
kthreadd_task gets initialized and wake_up_process(kthreadd_task) failes in
kthread_create_on_node().

Best regards
Christian Jann