Re: CVS commit: src/sys/dev/scsipi

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Thu, Apr 19, 2012 at 04:41:04PM +1000, matthew green wrote:
> 
> > Module Name:        src
> > Committed By:       bouyer
> > Date:               Wed Apr 18 20:37:49 UTC 2012
> > 
> > Modified Files:
> >     src/sys/dev/scsipi: scsipi_base.c
> > 
> > Log Message:
> > Fix KASSERT(): autoconf doesn't run under the KERNEL_LOCK
> 
> this is true, but can you please fix it differently?  ie autoconf
> isn't "cold".  most of scsi autoconf runs after cold is gone, so
> i'd rather make whatever callers deal with it so that they work
> cold or not.

But if we're not cold, interrupts are enabled so I hope whatever calls
into scsi autoconf runs under the big lock if the underlying driver
isn't SMP-safe (and if it is, it's its job to take the KERNEL_LOCK).

The problem I've seen is with a driver I'm working on, similar to mfi(4)
(and I suspect mfi(4) would have had the same problem):
the driver's attach calls config_found_sm_loc() to attach the scsibus
while cold, so the big lock isn't helt at this point.

If the driver's attach is called after cold (e.g. after a detach/rescan
of the pci bus), the driver's attach should be called with KERNEL_LOCK
held, or bad things may happen when interrupts are enabled for this driver.

What kind of senario do you have in mind ?

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--