Re: [PATCH] Readd BUG for SMP TLB IPI

[Andi Kleen <ak@suse.de>]

On 09 Jul 2003 18:04:15 +0100
Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:

> On Mer, 2003-07-09 at 17:58, Andi Kleen wrote:
> > > It can happen to any PII/PIII box, its just very very rare on others, so
> > > rare I guess such crashes are in the noise.
> > 
> > How do you know it an happen on them? Do you have backtraces?
> 
> I sat down with a BP6 owner and did lots of debugging.

I meant on the not known-to-be-nearly-unusable boards. Or are you saying that
on the other boards the APIC bus could be lossy too, but it's very unlikely? 

[my personal feeling would be to consider the lossy APIC bus to be a hardware
problem, like an MCE that cannot be really handled] 

> > If the BUG was there they wouldn't be in the noise.  With the incomplete/broken
> > handling it's just a silent hang.
> 
> I'm not arguing BUG is better than hang, but working right is better than BUG 8)

I suspect when you have a lossy APIC bug you will run into problems with other IPIs too,
it's really an uphill fight which you are likely to lose.

Anyways, having a clear BUG will make it easier to evaluate if there is really
a problem.

-Andi