Re: [KGDB PATCH][7/7] Move debugger_entry()

[Tom Rini <trini@kernel.crashing.org>]

On Fri, Mar 12, 2004 at 10:12:34AM +0530, Amit S. Kale wrote:
> On Friday 12 Mar 2004 2:54 am, George Anzinger wrote:
> > Amit S. Kale wrote:
> > > On Wednesday 03 Mar 2004 6:38 am, George Anzinger wrote:
> > >>Amit S. Kale wrote:
> > >>>OK to checkin.
> > >>>
> > >>>-Amit
> > >>>
> > >>>On Saturday 28 Feb 2004 3:24 am, Tom Rini wrote:
> > >>>>Hello.  When we use kgdboe, we can't use it until do_basic_setup() is
> > >>>>done. So we have two options, not allow kgdboe to use the initial
> > >>>>breakpoint or move debugger_entry() to be past the point where kgdboe
> > >>>>will be usable. I've opted for the latter, as if an earlier breakpoint
> > >>>>is needed you can still use serial and throw
> > >>>>kgdb_schedule_breakpoint/breakpoint where desired.
> > >>>>
> > >>>>--- linux-2.6.3-rc4/init/main.c	2004-02-17 09:51:19.000000000 -0700
> > >>>>+++ linux-2.6.3-rc4-kgdb/init/main.c	2004-02-17 11:33:51.854388988
> > >>>> -0700 @@ -581,6 +582,7 @@ static int init(void * unused)
> > >>>>
> > >>>>	smp_init();
> > >>>>	do_basic_setup();
> > >>>>+	debugger_entry();
> > >>
> > >>It would be nice to not need this.  Could it be a side effect of
> > >>configuring the interface or some such so we don't have to patch
> > >>init/main.c
> > >
> > > I attempted doing this when I was trying to code a netpoll independent
> > > ethernet interface. I couldn't do without it. I needed one hook to kgdb
> > > in init to mark completion of smp_init. If an interface was ready, that
> > > hook called breakpoint. A similar hook was placed in interface
> > > initialization code, it called breakpoint, if kgdb core was ready on
> > > account of smp_init completion.
> >
> > I guess the real question is why do you need to wait so long?  What is it
> > that needs to be done prior to this call?
> 
> 2.4.x kgdb legacy code! That was needed in some early 2.4 kgdbs. Perhaps we 
> can move it earlier now. If someone tests the patch on an smp machine and 
> confirms that it works, I'll be happy change it.

It's only legacy code under the following conditions (with current code):
- You don't care about getting an initial break from kgdboe (fixable...)
- kgdb_arch_init sets up kgdb_serial to an I/O that is suitably used
  early on.

-- 
Tom Rini
http://gate.crashing.org/~trini/