On Sat, 8 Aug 2015, Greg Andrzejewski wrote:
> Jumping in to MacsBug on reboot, I found this in __log_buf:
>
> Displaying memory from 3240d0
> 003240D0 0000 0000 0000 0000 004C 003B 0000 0033 .........L.;...3
> 003240E0 4255 473A 2073 6368 6564 756C 696E 6720 BUG: scheduling
> 003240F0 7768 696C 6520 6174 6F6D 6963 3A20 286E while atomic: (n
> 00324100 756C 6C29 2F2D 3136 3232 3532 3337 3736 ull)/-1622523776
> 00324110 2F30 7834 3038 3032 3666 3200 0000 0000 /0x408026f2.....
> 00324120 0000 0000 0022 0012 0000 0014 4D6F 6475 ....."......Modu
> 00324130 6C65 7320 6C69 6E6B 6564 2069 6E3A 0000 les linked in:..
> 00324140 0000 0000 0000 0058 0048 0000 0034 4350 .......X.H...4CP
> 00324150 553A 2030 2050 4944 3A20 3133 3232 3638 U: 0 PID: 132268
> 00324160 3630 3138 2043 6F6D 6D3A 2020 4E6F 7420 6018 Comm: Not
> 00324170 7461 696E 7465 6420 342E 312E 302D 312D tainted 4.1.0-1-
> 00324180 6D36 386B 2023 3120 4465 6269 616E 2034 m68k #1 Debian 4
> 00324190 2E31 2E33 2D31 0000 0000 0000 0000 0000 .1.3-1..........
>
> Signs of life! If the scheduler's starting, we're way past the early
> init stuff, right? Just to be sure, I powered down, verified that region
> of memory was trashed, and tried booting again. Same message.
Nice going!
>
> I was confused at first, because I wasn't seeing all the earlyprintk
> stuff (ABCDEFG...) in the buffer. Then it dawned on me to check if any
> of that stuff goes actually through the log buffer or just directly to
> the console/serial port, and it appears to be the latter. Maybe it needs
> to, but if that were easy/a-good-idea I'd have to imagine it'd be doing
> it already.
I don't know how __log_buf relates to the consoles. Certainly the
"ABCDEFG" is generated before the early console starts. The early console
is normally disabled when tty0 (framebuffer console) or ttyS0 (serial
console) starts up.
If you want to see all kernel messages on the serial console, and then get
a login prompt at the serial console, you need to boot with arguments
"earlyprintk console=tty0 console=ttyS0"
If you want to see all kernel messages on the serial console, but with
login prompt at the framebuffer console, use
"earlyprintk console=ttyS0 console=tty0"
> Guess I could give it a shot, but time's probably better spent figuring
> out what's going on with the display and serial port.
>
I agree. And that reminds me: the Quadra 900 and 950 have an SCC IOP, like
the Mac IIfx. That means you must tell MacOS to switch the serial ports to
IOP-bypass ("compatible") mode. Otherwise the serial port won't work. (I
don't know whether this applies to EMILE.)
There is a control panel for that called Serial Switch, IIRC. That should
get you a working serial console, and a backtrace. I'd be interested to
know whether v3.x kernels also fail with the same BUG splat.
I can't explain why there is no output on the framebuffer. Lots of other
Quadras have a DAFB chip and they generally work OK. Maybe try a different
video mode and/or color depth? Since you have no expansion cards
installed, I don't know what else to try.
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