From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 20 Nov 2006 17:28:24 +0000 (GMT) From: Hugh Dickins Subject: Re: build error: sparsemem + SLOB In-Reply-To: Message-ID: References: <20061119210545.9708e366.randy.dunlap@oracle.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Christoph Lameter Cc: Randy Dunlap , linux-mm@kvack.org, mpm@selenic.com, Pekka Enberg List-ID: On Mon, 20 Nov 2006, Christoph Lameter wrote: > > As far as I can tell SLOB is fundamentally racy since it does not support > SLAB_DESTROY_BY_RCU correctly. F.e. The constructor for the anon_vma will > be called on alloc without regard for RCU, we free an item and reuse it > without regard to RCU. This can potentially mess up the anon_vma locking > state while we access it. Good find! > Is SLOB used at all or have we been lucky so far? Lucky so far. Well, we'd actually have to be quite unlucky to ever see what page_lock_anon_vma/SLAB_DESTROY_BY_RCU are guarding against. But you're absolutely right that users should not be exposed to such unsafety. I'd say SLOB should be disallowed if SMP. Hugh -- 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