From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sc8-sf-mx1-b.sourceforge.net ([10.3.1.91] helo=mail.sourceforge.net) by sc8-sf-list1-new.sourceforge.net with esmtp (Exim 4.43) id 1Kaodu-0001jd-2G for user-mode-linux-devel@lists.sourceforge.net; Wed, 03 Sep 2008 02:27:14 -0700 Received: from wa-out-1112.google.com ([209.85.146.179]) by mail.sourceforge.net with esmtp (Exim 4.44) id 1Kaods-0004lo-O6 for user-mode-linux-devel@lists.sourceforge.net; Wed, 03 Sep 2008 02:27:14 -0700 Received: by wa-out-1112.google.com with SMTP id j5so2261845wah.18 for ; Wed, 03 Sep 2008 02:27:12 -0700 (PDT) Message-ID: <84144f020809030227jce7d3c2wab9e9c00b2fcdfe5@mail.gmail.com> Date: Wed, 3 Sep 2008 12:27:12 +0300 From: "Pekka Enberg" In-Reply-To: MIME-Version: 1.0 Content-Disposition: inline References: <84144f020808300350i7cb2d23aj6d1ffcbeceaf7e9c@mail.gmail.com> Subject: Re: [uml-devel] [PATCH 5/6] slab: Annotate slab List-Id: The user-mode Linux development list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: user-mode-linux-devel-bounces@lists.sourceforge.net Errors-To: user-mode-linux-devel-bounces@lists.sourceforge.net To: Steve VanDeBogart Cc: user-mode-linux-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, "Paul E. McKenney" , Ingo Molnar , dkegel@google.com, jiayingz@google.com Hi Steve, On Wed, Sep 3, 2008 at 8:08 AM, Steve VanDeBogart wrote: > Thank you for pointing out the location of the kmemcheck code. I looked > around briefly but didn't find the latest version. It does seem that > kmemcheck and Valgrind annotations want to live in the same places so it > makes perfect sense to combine them where possible. I'm not exactly sure > what you find so ugly about the Valgrind annotations, please elaborate. Upper case macros and littering #ifdefs in the code. See the kmemcheck hooks how to do it in a clean way. On Wed, Sep 3, 2008 at 8:08 AM, Steve VanDeBogart wrote: > It is true that code above the allocator should not be touching free'd > slab objects. However, it is also true that objects from slabs that > have a constructor should retain their per byte un/initialized state > through allocation and free cycles (just the semantic of slabs with > constructors AFAICT). Sorry for being unclear, sure, object should be marked as initialized when they're returned from kmem_cache_alloc(). However, what I disagree with is *where* you're marking them as initialized. Surely they're not semantically initialized when the slabs are allocated (although technically they are). On Wed, Sep 3, 2008 at 8:08 AM, Steve VanDeBogart wrote: > Ideally, we'd tell Valgrind that the bytes of a free'd slab object are > no longer accessible, but the initialized state should remain the same > until the object is made accessible again by the next allocation of > the object. Unfortunately, the compression method for A & V bits in > Valgrind doesn't allow a region to be inaccessible and retain validness > bits. I don't see why you should mark them initialized all the time. Just mark them as uninitialized on kmem_cache_free() and again as initialized when they're about to be returned from kmem_cache_alloc() like we do in kmemcheck. Pekka ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel