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 SMTP id 70BF66B01F0 for ; Fri, 27 Aug 2010 15:29:33 -0400 (EDT) Date: Fri, 27 Aug 2010 14:29:28 -0500 (CDT) From: Christoph Lameter Subject: Re: [PATCH] mm: fix hang on anon_vma->root->lock In-Reply-To: Message-ID: References: <20100826235052.GZ6803@random.random> <20100827095546.GC6803@random.random> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org To: Hugh Dickins Cc: Andrea Arcangeli , Linus Torvalds , Andrew Morton , Rik van Riel , Peter Zijlstra , linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: On Fri, 27 Aug 2010, Hugh Dickins wrote: > Eh? My solution was a second page_mapped(page) test i.e. testing an atomic. Argh. Right. Looked like a global to me. Did not see the earlier local def. If you still use a pointer then what does insure that the root pointer was not changed after the ACCESS_ONCE? The free semantics of an anon_vma? Since there is no lock taken before the mapped check none of the earlier reads from the anon vma structure nor the page mapped check necessarily reflect a single state of the anon_vma. -- 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