From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 17 Apr 2008 19:14:43 +0200 From: Andrea Arcangeli Subject: Re: [PATCH 1 of 9] Lock the entire mm to prevent any mmu related operation to happen Message-ID: <20080417171443.GM17187@duo.random> References: <20080416163337.GJ22493@sgi.com> <20080417155157.GC17187@duo.random> <20080417163642.GE11364@sgi.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080417163642.GE11364@sgi.com> Sender: owner-linux-mm@kvack.org Return-Path: To: Robin Holt Cc: Christoph Lameter , akpm@linux-foundation.org, Nick Piggin , Steve Wise , Peter Zijlstra , linux-mm@kvack.org, Kanoj Sarcar , Roland Dreier , Jack Steiner , linux-kernel@vger.kernel.org, Avi Kivity , kvm-devel@lists.sourceforge.net, general@lists.openfabrics.org, Hugh Dickins List-ID: On Thu, Apr 17, 2008 at 11:36:42AM -0500, Robin Holt wrote: > In this case, we are not making the call to unregister, we are waiting > for the _release callout which has already removed it from the list. > > In the event that the user has removed all the grants, we use unregister. > That typically does not occur. We merely wait for exit processing to > clean up the structures. Then it's very strange. LIST_POISON1 is set in n->next. If it was a second hlist_del triggering the bug in theory list_poison2 should trigger first, so perhaps it's really a notifier running despite a mm_lock is taken? Could you post a full stack trace so I can see who's running into LIST_POISON1? If it's really a notifier running outside of some mm_lock that will be _immediately_ visible from the stack trace that triggered the LIST_POISON1! Also note, EMM isn't using the clean hlist_del, it's implementing list by hand (with zero runtime gain) so all the debugging may not be existent in EMM, so if it's really a mm_lock race, and it only triggers with mmu notifiers and not with EMM, it doesn't necessarily mean EMM is bug free. If you've a full stack trace it would greatly help to verify what is mangling over the list when the oops triggers. Thanks! Andrea -- 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