Subject: Re: [PATCH] powerpc: set the correct ksp_limit on ppc32 when switching to irq stack

From: Guenter Roeck <[email-masked]>
Date: Tue, 21 Jan 2014 08:14:50 -0800

On Fri, Jan 17, 2014 at 12:25:28PM +0800, Kevin Hao wrote:
> Guenter Roeck has got the following call trace on a p2020 board:
>   Kernel stack overflow in process eb3e5a00, r1=eb79df90
>   CPU: 0 PID: 2838 Comm: ssh Not tainted 3.13.0-rc8-juniper-00146-g19eca00 #4
>   task: eb3e5a00 ti: c0616000 task.ti: ef440000
>   NIP: c003a420 LR: c003a410 CTR: c0017518
>   REGS: eb79dee0 TRAP: 0901   Not tainted (3.13.0-rc8-juniper-00146-g19eca00)
>   MSR: 00029000 <CE,EE,ME>  CR: 24008444  XER: 00000000
>   GPR00: c003a410 eb79df90 eb3e5a00 00000000 eb05d900 00000001 65d87646 00000000
>   GPR08: 00000000 020b8000 00000000 00000000 44008442
>   NIP [c003a420] __do_softirq+0x94/0x1ec
>   LR [c003a410] __do_softirq+0x84/0x1ec
>   Call Trace:
>   [eb79df90] [c003a410] __do_softirq+0x84/0x1ec (unreliable)
>   [eb79dfe0] [c003a970] irq_exit+0xbc/0xc8
>   [eb79dff0] [c000cc1c] call_do_irq+0x24/0x3c
>   [ef441f20] [c00046a8] do_IRQ+0x8c/0xf8
>   [ef441f40] [c000e7f4] ret_from_except+0x0/0x18
>   --- Exception: 501 at 0xfcda524
>       LR = 0x10024900
>   Instruction dump:
>   7c781b78 3b40000a 3a73b040 543c0024 3a800000 3b3913a0 7ef5bb78 48201bf9
>   5463103a 7d3b182e 7e89b92e 7c008146 <3ba00000> 7e7e9b78 48000014 57fff87f
>   Kernel panic - not syncing: kernel stack overflow
>   CPU: 0 PID: 2838 Comm: ssh Not tainted 3.13.0-rc8-juniper-00146-g19eca00 #4
>   Call Trace:
> 
> The reason is that we have used the wrong register to calculate the
> ksp_limit in commit cbc9565ee826 (powerpc: Remove ksp_limit on ppc64).
> Just fix it.
> 
> As suggested by Benjamin Herrenschmidt, also add the C prototype of the
> function in the comment in order to avoid such kind of errors in the
> future.
> 
Was this patch accepted, or are there any problems with it ?
I didn't see any comments, and it still isn't upstream nor in linux-next.

Thanks,
Guenter