bug with 3.4.6, 3.5.3, 3.6.1

Gilles Chanteperdrix gilles.chanteperdrix at xenomai.org
Thu Oct 11 09:32:06 EDT 2012

On 10/11/2012 12:36 PM, Will Deacon wrote:
> On Thu, Oct 11, 2012 at 06:46:35AM +0100, Gilles Chanteperdrix wrote:
>> Hi,
> Hi Gilles,
>> when booting Linux v3.4.6, v3.5.3, or v3.6.1 on a pandaboard with an 
>> OMAP4430 ES2.1, compiled with the following configuration:
>> http://xenomai.org/~gch/config-panda
>> I get the bug below after mounting the root filesystem.
>> CONFIG_VMSPLIT_2G and CONFIG_THUMB2_KERNEL disabled seems to be the 
>> combination which triggers the bug.
>> With this configuration, it seems the init_mm.mm_count incrementation
>> done at the beginning of secondary_start_kernel() is "lost" after the
>> calls to cpu_switch_mm() and local_flush_tlb().
>> Modifying the secondary_startup() function in head.S to pass the 
>> swapper pgdir instead of the idmap pgdir in r4 also avoids the issue.
> What's your PHYS_OFFSET? I suspect it's >= 2GB, in which case I have some
> ideas about this problem.

Yes, according to /proc/iomem:
80000000-bfefffff : System RAM
  80008000-80339fff : Kernel code
  80364000-803c52e7 : Kernel data

So, PHYS_OFFSET is 0x80000000 that is, 2GB.


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