Re: Debugging kernel over serial console?

From: Riley Williams (rhw@MemAlpha.cx)
Date: Fri Jun 09 2000 - 04:28:40 EST


Hi Perry.

> [I'm reading L-K sort-of irregularly, so this is, uh, late.
> Still...]

8-)

>> How about making use of the so-called "break key" that can be
>> sent over the serial link by just about any terminal emulator?
>> When one is using a serial combination, the first character
>> after receipt of such is taken as being a SysRq code and acted
>> on as if pressed with SysRq.

> Be careful about doing something drastic when a serial line
> sees a "break". Depending on the kind of hardware involved,
> plugging and unplugging the serial line may be seen (by the
> serial chip) as a "break".

I would see something like this as being best implemented on the
basis of "BREAK puts us into SysRq mode with a timeout of (say)
15 seconds before we auto-revert to normal mode" to avoid things
like this. Even the slowest of typists should be able to press
the follow-up key within 15 seconds...

> Suns have this problem famously - they drop into the the
> PROM monitor on break, so (accidentally) unplugging a
> serial console terminal (or turning its power off) will
> freeze the machine until someone notices, plugs the
> terminal back in, and types "go"... at which point all the
> network connections usually have timed out. :-(

Ugh !!!

> To a blind optimist, an optimistic realist must seem like
> an Accursed Cynic.

All too true !!!

Best wishes from Riley.

 * Copyright (C) 2000, Memory Alpha Systems.
 * All rights and wrongs reserved.

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