Subject: Re: Warnings when booting rc5 on a mpc83xx based board

From: Nathan Lynch <[email-masked]>
Date: Tue, 16 Jan 2007 14:11:10 -0600

Joakim Tjernlund wrote:
> after upgrading to rc5 I get this:
> 
> IPIC (128 IRQ sources) at fdefd700
> QEIC (64 IRQ sources) at fdefc080
> PID hash table entries: 512 (order: 9, 2048 bytes)
> ------------[ cut here ]------------
> Badness at c00f4278 [verbose debug info unavailable]
> Call Trace:
> [C0249DC0] [C00085BC] show_stack+0x48/0x194 (unreliable)
> [C0249DF0] [C00F2158] report_bug+0x84/0xac
> [C0249E00] [C000DD28] program_check_exception+0xe0/0x538
> [C0249E40] [C000F78C] ret_from_except_full+0x0/0x4c
> --- Exception: 700 at kref_get+0xc/0x24
>     LR = of_node_get+0x20/0x38
> [C0249F00] [FFFFFFFF] 0xffffffff (unreliable)
> [C0249F10] [C000CCA0] of_find_node_by_type+0x8c/0xd0
> [C0249F30] [C02198A0] get_freq+0x2c/0x80
> [C0249F50] [C021992C] generic_calibrate_decr+0x38/0xdc
> [C0249F70] [C0219E5C] time_init+0x48c/0x530
> [C0249FD0] [C02135F4] start_kernel+0x120/0x250
> [C0249FF0] [00003438] 0x3438

Looks like it could be an unbalanced of_node_put causing a node's
refcount to underflow, probably the root node.  The warning in
kref_get has unearthed a couple of these recently, see

http://patchwork.ozlabs.org/linuxppc/patch?id=8840

for example.