From mboxrd@z Thu Jan 1 00:00:00 1970 From: Russell King - ARM Linux Subject: Re: alignment faults in 3.6 Date: Fri, 12 Oct 2012 13:24:02 +0100 Message-ID: <20121012122402.GI21164@n2100.arm.linux.org.uk> References: <20121005082439.GF4625@n2100.arm.linux.org.uk> <201210120811.43290.arnd@arndb.de> <20121012090321.GA21164@n2100.arm.linux.org.uk> <1350036263.21172.11438.camel@edumazet-glaptop> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Arnd Bergmann , linux-arm-kernel@lists.infradead.org, =?iso-8859-1?Q?M=E5ns_Rullg=E5rd?= , David Laight , netdev@vger.kernel.org, Jon Masters To: Eric Dumazet Return-path: Received: from caramon.arm.linux.org.uk ([78.32.30.218]:51099 "EHLO caramon.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753512Ab2JLMY1 (ORCPT ); Fri, 12 Oct 2012 08:24:27 -0400 Content-Disposition: inline In-Reply-To: <1350036263.21172.11438.camel@edumazet-glaptop> Sender: netdev-owner@vger.kernel.org List-ID: On Fri, Oct 12, 2012 at 12:04:23PM +0200, Eric Dumazet wrote: > On Fri, 2012-10-12 at 10:03 +0100, Russell King - ARM Linux wrote: > > > No. It is my understanding that various IP option processing can also > > cause the alignment fault handler to be invoked, even when the packet is > > properly aligned, and then there's jffs2/mtd which also relies upon > > alignment faults being fixed up. > > Oh well. > > We normally make sure we dont have alignment faults on arches that dont > have CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS (or a non null NET_IP_ALIGN) > > So if you find an offender, please report a bug, because I can guarantee > you we will _fix_ it. I think one change I will make to the ARM alignment fixup is to get it to record the last PC where a misaligned kernel fault occurred, and report it via our statistics procfs file. That should allow us to track down where some of these occur. They aren't anywhere near regular though - looking at the statistics, my firewall seems to do an average of around 2-3 a day, and a web server around 7-8 a day.