From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753542Ab2GQHCM (ORCPT ); Tue, 17 Jul 2012 03:02:12 -0400 Received: from LGEMRELSE6Q.lge.com ([156.147.1.121]:48966 "EHLO LGEMRELSE6Q.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751401Ab2GQHBX (ORCPT ); Tue, 17 Jul 2012 03:01:23 -0400 X-AuditID: 9c930179-b7bdcae000003d91-be-50050dbf3840 From: Minchan Kim To: Kamezawa Hiroyuki , Mel Gorman Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , KOSAKI Motohiro , Hugh Dickins , Minchan Kim Subject: [RFC 3/3] memory-hotplug: bug fix race between isolation and allocation Date: Tue, 17 Jul 2012 16:01:45 +0900 Message-Id: <1342508505-23492-4-git-send-email-minchan@kernel.org> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1342508505-23492-1-git-send-email-minchan@kernel.org> References: <1342508505-23492-1-git-send-email-minchan@kernel.org> X-Brightmail-Tracker: AAAAAA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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; + } else if (page_count(page) == 0 && get_page_migratetype(page) == MIGRATE_ISOLATE) pfn += 1; -- 1.7.9.5