"Core" thread doesn't become active in kernel initialization

[Martin Stein]

Hi Bob,

On 03.07.2015 13:52, Bob Stewart wrote:
> Regarding possible issues with CXA guards, I did change the constructor 
> of Core_thread to be public and applied your [4] modification. That did 
> allow allow the kernel initialization to complete and I got the "kernel 
> initialized" message on the console. 

Nice! :)

> Now I need to study the guard code 
> to see what is going on.

Regarding the CXA guards: The reason why we have introduced the
unmanaged_singleton was that we already had troubles with the atomic
operations in the cmpxchg that is used by the guards. It was on the
Raspberry PI where atomic ops do not work until the caches are enabled.
Thus we replaced every static variable in an early called function by an
unmanaged_singleton. What made me rule out this explanation in your case
is that the problem definitely occurs after the MMU and thereby the
caches have been enabled (Cpu::init_virt_kernel in init_kernel_mp).

Did you change something regarding this, e.g. switched off caches in
[1]? Can you please post the output of [2]. It may also help if you
enable the hw_info test by doing [3] and post the output. If the hw_info
test gets stuck at any point before it prints "--- End ---" you can
uncomment the respective register read in [4] (some registers are not
accessible on all platforms).

Another idea: The atomic ops in ARM are realized through a so-called
"exclusive" state that a CPU can set. This state can be cleared via
assembly op "clrex". Maybe your exclusive state is erroneously set when
entering the kernel and clearing it right before [5] solves the problem.

Cheers,
Martin

[1]
Arm::Sctlr::init_common in
base-hw/src/core/include/spec/arm/cpu_support.h

[2]
PINF("Sctlr %x", Genode::Arm::Sctlr::read());
during init_kernel_mp_primary

[3]
cp base-hw/lib/mk/platform_panda/test-hw_info.mk
base-hw/lib/mk/platform_am437x/

[4] base-hw/src/test/hw_info/spec/arm_v7/info.cc

[5]
"ldr r0, =_bss_start" in
base-hw/src/core/spec/arm/kernel/crt0.s