From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail202.messagelabs.com (mail202.messagelabs.com [216.82.254.227]) by kanga.kvack.org (Postfix) with ESMTP id AABBB6B01B2 for ; Mon, 28 Jun 2010 05:03:23 -0400 (EDT) Received: from hpaq6.eem.corp.google.com (hpaq6.eem.corp.google.com [172.25.149.6]) by smtp-out.google.com with ESMTP id o5S93KWL030677 for ; Mon, 28 Jun 2010 02:03:20 -0700 Received: from pxi1 (pxi1.prod.google.com [10.243.27.1]) by hpaq6.eem.corp.google.com with ESMTP id o5S92lPe028682 for ; Mon, 28 Jun 2010 02:03:19 -0700 Received: by pxi1 with SMTP id 1so2949284pxi.1 for ; Mon, 28 Jun 2010 02:03:18 -0700 (PDT) Date: Mon, 28 Jun 2010 02:03:16 -0700 (PDT) From: David Rientjes Subject: Re: kmem_cache_destroy() badness with SLUB In-Reply-To: <1277688701.4200.159.camel@pasglop> Message-ID: References: <1277688701.4200.159.camel@pasglop> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org To: Benjamin Herrenschmidt Cc: linux-mm@kvack.org, Christoph Lameter , "linux-kernel@vger.kernel.org" List-ID: On Mon, 28 Jun 2010, Benjamin Herrenschmidt wrote: > Hi folks ! > > Internally, I'm hitting a little "nit"... > > sysfs_slab_add() has this check: > > if (slab_state < SYSFS) > /* Defer until later */ > return 0; > > But sysfs_slab_remove() doesn't. > > So if the slab is created -and- destroyed at, for example, arch_initcall > time, then we hit a WARN in the kobject code, trying to dispose of a > non-existing kobject. > Indeed, but shouldn't we be appropriately handling the return value of sysfs_slab_add() so that it fails cache creation? We wouldn't be calling sysfs_slab_remove() on a cache that was never created. > Now, at first sight, just adding the same test to sysfs_slab_remove() > would do the job... but it all seems very racy to me. > > I don't understand in fact how this slab_state deals with races at all. > All modifiers of slab_state are intended to be run only on the boot cpu so the only concern is the ordering. We need slab_state to indicate how far slab has been initialized since we can't otherwise enforce how code uses slab in between things like kmem_cache_init(), kmem_cache_init_late(), and initcalls on the boot cpu. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org