linux-kernel - Re: [microblaze-uclinux] Re: [PATCH 1/2] microblaze: add stack unwinder

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Date:	Fri, 16 Apr 2010 09:33:30 -0500
From:	"Steven J. Magnani" <steve@...idescorp.com>
To:	Michal Simek <monstr@...str.eu>
Cc:	linux-kernel@...r.kernel.org, microblaze-uclinux@...e.uq.edu.au
Subject: Re: [microblaze-uclinux] Re: [PATCH 1/2] microblaze: add stack
 unwinder

On Fri, 2010-04-16 at 10:32 +0200, Michal Simek wrote:
> Please apply this patch and do the same testing as I did.
> 
> diff --git a/arch/microblaze/kernel/reset.c b/arch/microblaze/kernel/reset.c
> index a1721a3..76f6587 100644
> --- a/arch/microblaze/kernel/reset.c
> +++ b/arch/microblaze/kernel/reset.c
> @@ -112,8 +112,8 @@ void of_platform_reset_gpio_probe(void)
>   void machine_restart(char *cmd)
>   {
>          printk(KERN_NOTICE "Machine restart...\n");
> +       machine_shutdown();
>          gpio_system_reset();
> -       dump_stack();
>          while (1)
>                  ;
>   }
> @@ -121,6 +121,7 @@ void machine_restart(char *cmd)
>   void machine_shutdown(void)
>   {
>          printk(KERN_NOTICE "Machine shutdown...\n");
> +       dump_stack();
>          while (1)
>                  ;
>   }

I get this:

Call Trace:
[<20003008>] microblaze_unwind+0x68/0x94
[<20002c24>] show_stack+0x134/0x174
[<20002c80>] dump_stack+0x1c/0x3c
[<20001d84>] machine_shutdown+0x30/0x40
[<20001dc0>] machine_restart+0x2c/0x48
[<2002a540>] kernel_restart+0x5c/0x80
[<2002a6b8>] sys_reboot+0x11c/0x218
SYSCALL
[<2d5c0248>] PID 118 [reboot]

Is your problem on a MMU or noMMU system?

If the unwinder stops early, it found a return address outside the
kernel text, or couldn't find the addik that creates a stack frame - but
there's not enough information here to tell what happened. In your case
the backtrace goes off the rails before getting to the frame for
dump_stack(), which is where the stack dump begins. We'd need to see the
21 words preceding the dump (show_stack's frame is 13 words, and
microblaze_unwind's is 8) to know why.

Can you uncomment the #define DEBUG in unwind.c and try it again?

Thanks,
------------------------------------------------------------------------
 Steven J. Magnani               "I claim this network for MARS!
 www.digidescorp.com              Earthling, return my space modulator!"

 #include <standard.disclaimer>

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