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 ESMTP id 24E569000BD for ; Tue, 27 Sep 2011 22:45:38 -0400 (EDT) Received: from m3.gw.fujitsu.co.jp (unknown [10.0.50.73]) by fgwmail5.fujitsu.co.jp (Postfix) with ESMTP id 6C3753EE0AE for ; Wed, 28 Sep 2011 11:45:34 +0900 (JST) Received: from smail (m3 [127.0.0.1]) by outgoing.m3.gw.fujitsu.co.jp (Postfix) with ESMTP id 540C345DEB4 for ; Wed, 28 Sep 2011 11:45:34 +0900 (JST) Received: from s3.gw.fujitsu.co.jp (s3.gw.fujitsu.co.jp [10.0.50.93]) by m3.gw.fujitsu.co.jp (Postfix) with ESMTP id 3AD6945DE7E for ; Wed, 28 Sep 2011 11:45:34 +0900 (JST) Received: from s3.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s3.gw.fujitsu.co.jp (Postfix) with ESMTP id 2E9EB1DB803E for ; Wed, 28 Sep 2011 11:45:34 +0900 (JST) Received: from m107.s.css.fujitsu.com (m107.s.css.fujitsu.com [10.240.81.147]) by s3.gw.fujitsu.co.jp (Postfix) with ESMTP id F048C1DB803B for ; Wed, 28 Sep 2011 11:45:33 +0900 (JST) Message-ID: <4E828AFC.7070405@jp.fujitsu.com> Date: Wed, 28 Sep 2011 11:48:28 +0900 From: KOSAKI Motohiro MIME-Version: 1.0 Subject: Re: [PATCH] vmscan: add barrier to prevent evictable page in unevictable list References: <1317174330-2677-1-git-send-email-minchan.kim@gmail.com> <4E8284C6.1050900@jp.fujitsu.com> <20110928022510.GB12100@barrios-desktop> In-Reply-To: <20110928022510.GB12100@barrios-desktop> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: minchan.kim@gmail.com Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, jweiner@redhat.com, mel@csn.ul.ie, riel@redhat.com, lee.schermerhorn@hp.com (2011/09/28 11:25), Minchan Kim wrote: > On Wed, Sep 28, 2011 at 11:21:58AM +0900, KOSAKI Motohiro wrote: >> (2011/09/28 10:45), Minchan Kim wrote: >>> When racing between putback_lru_page and shmem_unlock happens, >>> progrom execution order is as follows, but clear_bit in processor #1 >>> could be reordered right before spin_unlock of processor #1. >>> Then, the page would be stranded on the unevictable list. >>> >>> spin_lock >>> SetPageLRU >>> spin_unlock >>> clear_bit(AS_UNEVICTABLE) >>> spin_lock >>> if PageLRU() >>> if !test_bit(AS_UNEVICTABLE) >>> move evictable list >>> smp_mb >>> if !test_bit(AS_UNEVICTABLE) >>> move evictable list >>> spin_unlock >>> >>> But, pagevec_lookup in scan_mapping_unevictable_pages has rcu_read_[un]lock so >>> it could protect reordering before reaching test_bit(AS_UNEVICTABLE) on processor #1 >>> so this problem never happens. But it's a unexpected side effect and we should >>> solve this problem properly. >> >> Do we still need this after Hannes removes scan_mapping_unevictable_pages? > > Hi KOSAKI, > > What Hannes removes is scan_zone_unevictable_pages not scan_mapping_unevictable_pages. > Oops, you are right. -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org