From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pete Zaitcev Subject: Re: [2.6.24 REGRESSION] BUG: Soft lockup - with VFS Date: Mon, 11 Feb 2008 18:12:54 -0800 Message-ID: <20080211181254.5029b8b4.zaitcev@redhat.com> References: <6101e8c40802051348w2250e593x54f777bb771bd903@mail.gmail.com> <20080205140506.c6354490.akpm@linux-foundation.org> <20080208234619.385bcab9.zaitcev@redhat.com> <20080212104612S.fujita.tomonori@lab.ntt.co.jp> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, oliver.pntr-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, jmorris-gx6/JNMH7DfYtjvyW6yDsg@public.gmane.org, linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, zaitcev-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org To: FUJITA Tomonori Return-path: In-Reply-To: <20080212104612S.fujita.tomonori-Zyj7fXuS5i5L9jVzuh4AOg@public.gmane.org> Sender: linux-usb-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-fsdevel.vger.kernel.org On Tue, 12 Feb 2008 10:46:12 +0900, FUJITA Tomonori wrote: > On a serious note, it seems that two scatter lists per request leaded > to this bug. Can the scatter list in struct ub_request be removed? Good question. It's an eyesore to be sure. The duplication exists for the sake of retries combined with the separation of requests from commands. Please bear with me, if you're curious: commands can be launched without requests (at probe time, for instance, or when sense is requested). So, they need an s/g table. But then, the lifetime of a request is greater than than of a command, in case of a retry especially. Therefore a request needs the s/g table too. So, one way to kill this duplication is to mandate that a request existed for every command. It seemed like way more code than just one memcpy() when I wrote it. Another way would be to make commands flexible, e.g. sometimes with just a virtual address and size, sometimes with an s/g table. If you guys make struct scatterlist illegal to copy with memcpy one day, this is probably what I'll do. -- Pete