Subject: Re: [RFC] consistent_sync and non L1 cache line aligned buffers

From: Matt Porter <[email-masked]>
Date: Tue, 15 Jul 2003 16:51:16 -0700

On Tue, Jul 15, 2003 at 09:27:10AM -0700, Eugene Surovegin wrote:
>
> At 09:17 AM 7/15/2003, Matt Porter wrote:
> >I'll agree that it's a better hack, but since the offending areas in
> >the SCSI subsystem are easily located, it seems wiser to fix upstream.
>
> Matt, the problem is it wasn't that *easy* to locate this, at least for me :)
> I'm not sure that this is the only place..

I didn't mean to trivialize the difficulty of finding this from the path
of tracking the symptom to the source. :)  I merely was pointing out
that now that you know the source of the problem, it's not *too* difficult
to look for buffers allocated on the stack by simple inspection of the
SCSI code.  I only jumped in on this because I felt a little guilty that
when I noticed this sometime back I got distracted and never tried to
send a patch to the maintainers. :-/

> >We still need someone with interest AND time to properly fix the
> >consistent alloc from irq issue. :)  All of the patches post to date
> >are incomplete bandaids.
>
> Uhh, I switched to solution which uses pre allocated consistent memory (10
> pages are enough for sym53c8xx_2).
> It's still not a generic solution, but at least it's safe :)

Are you doing this in the sym_2 driver or in the ppc consistent_*
implementations?  I only ask because I finally convinced myself
recently that attempting to make all the locking safe in the VM
subsystem was too much work.  I think Paul suggested at one point
that we might just preallocate a pool for atomic consistent allocations
anyway.

Regards,
--
Matt Porter
[email-masked]

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