Re: [discuss] Re: kgdb for x86_64 2.6 kernels

[George Anzinger <george@mvista.com>]

Amit S. Kale wrote:
> On Wednesday 14 Jan 2004 2:56 am, George Anzinger wrote:
> 
>>Amit S. Kale wrote:
>>
>>>8250.patch changes generic 8250/16550 driver behavior only in following
>>>ways 1. It adds a function serial8250_release_irq to release those serial
>>>ports which share an irq with kgdb irq.
>>>2. There are checks so that a serial port that uses an irq used by an
>>>initialized kgdb can't be initialized or started.
>>>
>>>File kgdb_8250.c is independent of 8250.c kgdb_8250.c depends on
>>>KGDB_8250 and 8250.c depends on SERIAL_8250 which can be independently
>>>configured. kgdb_8250.c can be compiled even if 8250.c is not included.
>>>kgdb_8250.c does only the _minimum_ set of initializations required by
>>>hardware.
>>
>>Ok.
>>
>>
>>>Serial interface should be configurable independent of kgdb and may not
>>>be configured if ethernet interface is configured.  Serial interface is
>>>far simpler hence superior for debugging purposes. If it's available,
>>>using ethernet interface is out of question. Ethernet interface can be
>>>used when serial hardware isn't present or is being used for some other
>>>purposes.
>>
>>I rather think that the serial inteface should be the fall back unless the
>>user has told us at configure time that it is not available.  I am not
>>prepared to make a statment that it is better than eth.  The eth intface
>>should be much faster, but it has its fingers into a large part of the
>>kernel that MAY be the subject of the current session.  Thus, I think that
>>eth may be better, IF one is clearly not involved in debugging those areas
>>of the kernel.  (Which, by the way, we need to enumerate at some point.)
> 
> 
> Ethernet interface spans a large part of the kernel, so is going to be limited 
> in near future. When it becomes as minimal as the serial interface, both may 
> be given equal priority.
> 
> At 115kbps, serial interface is usable even when doing a thread list of 200 
> threads.

Only 200? :)

Yes, I agree, but the thing I see about the eth interface is that it allows much 
more remote debugging, like accrost the country, and it is every so much easier 
to set up.  I don't know about you, but my experience with rs232, which after 
all, can only be wired one of two ways, it that the probability of getting it 
wrong is about 90%.

-g
-- 
George Anzinger   george@mvista.com
High-res-timers:  http://sourceforge.net/projects/high-res-timers/
Preemption patch: http://www.kernel.org/pub/linux/kernel/people/rml