Re: [PATCH 1/1] 8250_kgdb driver reworked

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

On Thu, Sep 01, 2005 at 11:44:44PM +0100, Alan Cox wrote:
> On Iau, 2005-09-01 at 14:47 -0700, Tom Rini wrote:
> > > > +	 * If  there is some other CPU in KGDB then this is a
> > > > +	 * spurious interrupt. so return without even checking a byte
> > > > +	 */
> > > > +	if (atomic_read(&debugger_active))
> > > > +		return IRQ_NONE;
> > > > +
> > > 
> > > Shared IRQ -> hung box. 
> > 
> > Can you elaborate a bit more please?  When we're actually in KGDB and
> > working on stuff we're polling so it's really just the
> > GDB-is-interrupting case.
> 
> If the IRQ source is level triggered and the device is the cause then as
> soon as you exit the IRQ handler, you'll be called again and again and
> again until the IRQ is cleared or 10,000 tries or so occur when the IRQ
> is disabled

But in the shared IRQ and other source is the other uart still
registered to the real 8250 driver, we'd luck out.  I know this has been
tested on a shared serial irq box, so it's not immediate and always
death at least...

> Does this only occur if there is a stray IRQ under delivery as kgdb is
> entered ? (ie you do something like

So digging back in CVS it seems this was added to fix a spurious
interrupt that occured on an (probably) an x86_64 box when NMI support
didn't work correctly.  I think it's safe enough to just drop this.

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