From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nishanth Aravamudan Subject: Re: kernel unaligned accesses on IA64 in IDE Date: Fri, 22 Aug 2008 14:38:12 -0700 Message-ID: <20080822213812.GC11781@us.ibm.com> References: <20080819225606.GB22088@us.ibm.com> <20080822164538.GB9047@us.ibm.com> <9ea470500808221029l6bd79c62w4c06d948f962d95c@mail.gmail.com> <200808222036.00536.bzolnier@gmail.com> <57C9024A16AD2D4C97DC78E552063EA309EDE187@orsmsx505.amr.corp.intel.com> <200808222036.m7MKa6bT008897@agluck-lia64.sc.intel.com> <20080822205431.GA5968@gollum.tnic> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from e6.ny.us.ibm.com ([32.97.182.146]:53433 "EHLO e6.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754896AbYHVVim (ORCPT ); Fri, 22 Aug 2008 17:38:42 -0400 Content-Disposition: inline In-Reply-To: <20080822205431.GA5968@gollum.tnic> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Borislav Petkov Cc: "Luck, Tony" , Robin Holt , Bartlomiej Zolnierkiewicz , "linux-ia64@vger.kernel.org" , "linux-ide@vger.kernel.org" , FUJITA Tomonori 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 IBM Linux Technology Center