Re: 2.6.30-rc1: invalid opcode with call trace

[Ingo Molnar <mingo@elte.hu>]

* Jens Axboe <jens.axboe@oracle.com> wrote:

> On Wed, Apr 08 2009, Ingo Molnar wrote:
> > 
> > * Ingo Molnar <mingo@elte.hu> wrote:
> > 
> > > I too have an async hang/crash, on an old-style SCSI (aic7xxx) box 
> > > - hang log attached below.
> > > [...]
> > >
> > > ( Full bootlog attached below as well - i'm sending the config as a 
> > >   reply as this mail is close to lkml size limits already. )
> > 
> > Config attached.
> > 
> >  known bad  : v2.6.29-9854-gd508afb
> >  known good : v2.6.29
> > 
> > Suspected commit introducing the regression:
> > 
> >  9710794: async: remove the temporary (2.6.29) "async is off by default" code
> > 
> > (i'll now try a revert of this.)
> 
> That's what I figured was the culprit as well, but that does not 
> really tell us anything about what part of async.c is buggy :-)

async.c itself is likely not to be buggy - fundamental bugs that 
deep in the center of the kernel usually cannot hide for long :-)

What matters more is the _effects_ of having async bootup now, on 
various subsystems it interacts with. Unexpected parallelism and 
reordering between init sequences.

It would have been far better to not have such a 'flip the switch 
on' moment - but instead a more gradual step by step introduction of 
async bootup, with accompanied strong testing.

	Ingo