From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx152.postini.com [74.125.245.152]) by kanga.kvack.org (Postfix) with SMTP id 13CD56B005D for ; Tue, 17 Jul 2012 06:13:19 -0400 (EDT) Received: by wgbdt14 with SMTP id dt14so218504wgb.26 for ; Tue, 17 Jul 2012 03:13:17 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <1342508505-23492-4-git-send-email-minchan@kernel.org> References: <1342508505-23492-1-git-send-email-minchan@kernel.org> <1342508505-23492-4-git-send-email-minchan@kernel.org> Date: Tue, 17 Jul 2012 18:13:17 +0800 Message-ID: Subject: Re: [RFC 3/3] memory-hotplug: bug fix race between isolation and allocation From: Bob Liu Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Minchan Kim Cc: Kamezawa Hiroyuki , Mel Gorman , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , KOSAKI Motohiro , Hugh Dickins Hi Minchan, On Tue, Jul 17, 2012 at 3:01 PM, Minchan Kim wrote: > Like below, memory-hotplug makes race between page-isolation > and page-allocation so it can hit BUG_ON in __offline_isolated_pages. > > CPU A CPU B > > start_isolate_page_range > set_migratetype_isolate > spin_lock_irqsave(zone->lock) > > free_hot_cold_page(Page A) > /* without zone->lock */ > migratetype = get_pageblock_migratetype(Page A); > /* > * Page could be moved into MIGRATE_MOVABLE > * of per_cpu_pages > */ > list_add_tail(&page->lru, &pcp->lists[migratetype]); > > set_pageblock_isolate > move_freepages_block > drain_all_pages > > /* Page A could be in MIGRATE_MOVABLE of free_list. */ > > check_pages_isolated > __test_page_isolated_in_pageblock > /* > * We can't catch freed page which > * is free_list[MIGRATE_MOVABLE] > */ > if (PageBuddy(page A)) > pfn += 1 << page_order(page A); > > /* So, Page A could be allocated */ > > __offline_isolated_pages > /* > * BUG_ON hit or offline page > * which is used by someone > */ > BUG_ON(!PageBuddy(page A)); > > Signed-off-by: Minchan Kim > --- > I found this problem during code review so please confirm it. > Kame? > > mm/page_isolation.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/mm/page_isolation.c b/mm/page_isolation.c > index acf65a7..4699d1f 100644 > --- a/mm/page_isolation.c > +++ b/mm/page_isolation.c > @@ -196,8 +196,11 @@ __test_page_isolated_in_pageblock(unsigned long pfn, unsigned long end_pfn) > continue; > } > page = pfn_to_page(pfn); > - if (PageBuddy(page)) > + if (PageBuddy(page)) { > pfn += 1 << page_order(page); > + if (get_page_migratetype(page) != MIGRATE_ISOLATE) > + break; > + } test_page_isolated() already have check get_pageblock_migratetype(page) != MIGRATE_ISOLATE. > else if (page_count(page) == 0 && > get_page_migratetype(page) == MIGRATE_ISOLATE) > pfn += 1; > -- > 1.7.9.5 > -- Regards, --Bob -- 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