From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with SMTP id 840F66B01F1 for ; Thu, 26 Aug 2010 02:41:34 -0400 (EDT) Date: Wed, 25 Aug 2010 23:41:49 -0700 (PDT) Message-Id: <20100825.234149.189710316.davem@davemloft.net> Subject: Re: [PATCH] mm: fix hang on anon_vma->root->lock From: David Miller In-Reply-To: References: Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: hughd@google.com Cc: torvalds@linux-foundation.org, akpm@linux-foundation.org, riel@redhat.com, aarcange@redhat.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: From: Hugh Dickins Date: Wed, 25 Aug 2010 23:12:54 -0700 (PDT) > After several hours, kbuild tests hang with anon_vma_prepare() spinning on > a newly allocated anon_vma's lock - on a box with CONFIG_TREE_PREEMPT_RCU=y > (which makes this very much more likely, but it could happen without). > > The ever-subtle page_lock_anon_vma() now needs a further twist: since > anon_vma_prepare() and anon_vma_fork() are liable to change the ->root > of a reused anon_vma structure at any moment, page_lock_anon_vma() > needs to check page_mapped() again before succeeding, otherwise > page_unlock_anon_vma() might address a different root->lock. > > Signed-off-by: Hugh Dickins Interesting, is the condition which allows this to trigger specific to this merge window or was it always possible? -- 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