Re: kernel unaligned accesses on IA64 in IDE

[Nishanth Aravamudan <nacc@us.ibm.com>]

On 22.08.2008 [22:54:31 +0200], Borislav Petkov wrote:
> On Fri, Aug 22, 2008 at 01:36:06PM -0700, Luck, Tony wrote:
> > > How about long instead of int.  int leaves us with the possibility that
> > > something else will expect 8 byte alignment.
> > 
> > How about this?
> > 
> > Align __cmd to ward off kernel unaligned access consoles messages on
> > ia64 (and perhaps make an almost imperceptible performance improvement
> > on other architectures that can handle unaligned access, but do so
> > more slowly than aligned accesses).
> 
> By the way, i've been wondering, this unaligned access breaking should have
> happened earlier, how did we miss that? Nish, Robin, can you see that in some
> older logs?

I replied about this in a separate sub-thread, but you may not have been
on the direct Cc (though linux-ide should have been).

This all began because I noticed one of my automated test machines had
not successfully booted a kernel in some time. I investigated via
bisection and found that CONFIG_PRINTK_TIME=y was broken on my IA64 box.
With Tony and Peter Z's help, that bug was resolved, but then with the
console working, I noticed these unaligned accesses. Sorry if it seemed
like, from my posting, they were a regression, I did not mean to give
that impression.

They may have been there for some time, but I don't have any logs from
kernels before 2.6.27-rc3, because of the CONFIG_PRINTK_TIME=y breakage
(which was being set by default for this box). I could go back and try
older kernels, if you'd like, but it would take some time.

Thanks,
Nish

-- 
Nishanth Aravamudan <nacc@us.ibm.com>
IBM Linux Technology Center