Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755769AbZJFAcx (ORCPT ); Mon, 5 Oct 2009 20:32:53 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755280AbZJFAcw (ORCPT ); Mon, 5 Oct 2009 20:32:52 -0400 Received: from TYO202.gate.nec.co.jp ([202.32.8.206]:61647 "EHLO tyo202.gate.nec.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755298AbZJFAcv (ORCPT ); Mon, 5 Oct 2009 20:32:51 -0400 Date: Tue, 6 Oct 2009 09:12:54 +0900 From: Daisuke Nishimura To: Greg KH Cc: linux-kernel@vger.kernel.org, stable@kernel.org, stable-review@kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, KAMEZAWA Hiroyuki , Balbir Singh , Hugh Dickins , Johannes Weiner , Alok Kataria , Daisuke Nishimura Subject: Re: [000/136] 2.6.31.2-stable review Message-Id: <20091006091254.448d45e2.nishimura@mxp.nes.nec.co.jp> In-Reply-To: <20091002012911.GA18542@kroah.com> References: <20091002012911.GA18542@kroah.com> Organization: NEC Soft, Ltd. X-Mailer: Sylpheed 2.6.0 (GTK+ 2.10.14; i686-pc-mingw32) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2166 Lines: 53 Hi, Greg. Could you consider adding the following commit in linus-tree to 2.6.31-stable ? I've verified the commit can be applied onto v2.6.31.2. commit 31a5639623a487d6db996c8138c9e53fef2e2d91 Author: Daisuke Nishimura Date: Mon Sep 21 17:02:50 2009 -0700 mm: add_to_swap_cache() must not sleep After commit 355cfa73 ("mm: modify swap_map and add SWAP_HAS_CACHE flag"), read_swap_cache_async() will busy-wait while a entry doesn't exist in swap cache but it has SWAP_HAS_CACHE flag. Such entries can exist on add/delete path of swap cache. On add path, add_to_swap_cache() is called soon after SWAP_HAS_CACHE flag is set, and on delete path, swapcache_free() will be called (SWAP_HAS_CACHE flag is cleared) soon after __delete_from_swap_cache() is called. So, the busy-wait works well in most cases. But this mechanism can cause soft lockup if add_to_swap_cache() sleeps and read_swap_cache_async() tries to swap-in the same entry on the same cpu. This patch calls radix_tree_preload() before swapcache_prepare() and divides add_to_swap_cache() into two part: radix_tree_preload() part and radix_tree_insert() part(define it as __add_to_swap_cache()). Signed-off-by: Daisuke Nishimura Cc: KAMEZAWA Hiroyuki Cc: Balbir Singh Cc: Hugh Dickins Cc: Johannes Weiner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds This is a fix for a soft lockup bug introduced at 2.6.31-rc1. It was rare, but I saw the bug several times, and Alok-san reported me the bug also happens on Ubuntu 9.10(alpha). https://bugs.launchpad.net/ubuntu/+source/linux/+bug/433646 Thanks, Daisuke Nishimura. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/