Re: [PATCHSET] block: fix PIO cache coherency bug, take 2

[Russell King <rmk+lkml@arm.linux.org.uk>]

On Sun, Jun 04, 2006 at 12:41:19PM +0900, Tejun Heo wrote:
> Russell, can you please verify arm's flush_kernel_dcache_page()?

That should be fine from a theoretical standpoint, but I can't say much
more than that - I have _great_ difficulty in reproducing the problem
with IDE and as such I consider myself out of the game of testing for
this problem:

| Date:   Fri, 13 Jan 2006 22:02:15 +0000
| From:   Russell King <rmk+lkml@arm.linux.org.uk>
| To:     Tejun Heo <htejun@gmail.com>
| Subject: Re: [PATCHSET] block: fix PIO cache coherency bug
|
| On Sat, Jan 14, 2006 at 12:24:16AM +0900, Tejun Heo wrote:
| > Russell, can you please test whether this fixes the bug on arm?  If
| > this fixes the bug and people agree with the approach, I'll follow up
| > with patches for yet unconverted drivers and documentation update.
|
| Unfortunately, as I previously explained, I'm not able to test this.
| The reason is that in order to reproduce the bug, you need a system
| with a VIVT write-back write-allocate cache.
|
| Unfortunately, the few systems I have which have such a cache do not
| have IDE, SCSI nor SATA (not even PCMCIA.)  I suggest contacting the
| folk who reported the bug in the first instance.

You need to approach other members of the ARM community to test these
patches.  Unfortunately I don't have a list of who has found the problem
and who is in a state to be able to reproduce it - since most members
are embedded engineers, they tend to move on to other projects quite
rapidly.

What I suggest is that we just throw _something_ which looks right into
the kernel and see what happens.  I can't see any other possible way to
proceed, _especially_ as we've had 6 months of very little progress on
this issue.

> I tried to implement flush_anon_page() too but didn't know what to do
> with anon_vma object.

I'm not sure what this is about...

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:  2.6 Serial core