Messages in this thread Patch in this message | | | From | Minchan Kim <> | Subject | [PATCH 3/3] memory-hotplug: bug fix race between isolation and allocation | Date | Wed, 5 Sep 2012 16:26:02 +0900 |
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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 <minchan@kernel.org> --- 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)) { + if (get_page_migratetype(page) != MIGRATE_ISOLATE) + break; pfn += 1 << page_order(page); + } else if (page_count(page) == 0 && get_page_migratetype(page) == MIGRATE_ISOLATE) pfn += 1; -- 1.7.9.5
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