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

[George Anzinger]

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@xxxxxxxxxx
High-res-timers:  http://sourceforge.net/projects/high-res-timers/
Preemption patch: http://www.kernel.org/pub/linux/kernel/people/rml

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