From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f71.google.com (mail-pg0-f71.google.com [74.125.83.71]) by kanga.kvack.org (Postfix) with ESMTP id 86AD96B0279 for ; Wed, 24 May 2017 11:47:51 -0400 (EDT) Received: by mail-pg0-f71.google.com with SMTP id i63so115054776pgd.15 for ; Wed, 24 May 2017 08:47:51 -0700 (PDT) Received: from foss.arm.com (foss.arm.com. [217.140.101.70]) by mx.google.com with ESMTP id q5si438470pgs.129.2017.05.24.08.47.49 for ; Wed, 24 May 2017 08:47:50 -0700 (PDT) From: Punit Agrawal Subject: [PATCH] mm/migrate: Fix ref-count handling when !hugepage_migration_supported() Date: Wed, 24 May 2017 16:47:28 +0100 Message-Id: <20170524154728.2492-1-punit.agrawal@arm.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Punit Agrawal , will.deacon@arm.com, catalin.marinas@arm.com, manoj.iyer@arm.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, tbaicar@codeaurora.org, timur@qti.qualcomm.com, Joonsoo Kim , Naoya Horiguchi , Wanpeng Li , Christoph Lameter On failing to migrate a page, soft_offline_huge_page() performs the necessary update to the hugepage ref-count. When !hugepage_migration_supported() , unmap_and_move_hugepage() also decrements the page ref-count for the hugepage. The combined behaviour leaves the ref-count in an inconsistent state. This leads to soft lockups when running the overcommitted hugepage test from mce-tests suite. Soft offlining pfn 0x83ed600 at process virtual address 0x400000000000 soft offline: 0x83ed600: migration failed 1, type 1fffc00000008008 (uptodate|head) INFO: rcu_preempt detected stalls on CPUs/tasks: Tasks blocked on level-0 rcu_node (CPUs 0-7): P2715 (detected by 7, t=5254 jiffies, g=963, c=962, q=321) thugetlb_overco R running task 0 2715 2685 0x00000008 Call trace: [] dump_backtrace+0x0/0x268 [] show_stack+0x24/0x30 [] sched_show_task+0x134/0x180 [] rcu_print_detail_task_stall_rnp+0x54/0x7c [] rcu_check_callbacks+0xa74/0xb08 [] update_process_times+0x34/0x60 [] tick_sched_handle.isra.7+0x38/0x70 [] tick_sched_timer+0x4c/0x98 [] __hrtimer_run_queues+0xc0/0x300 [] hrtimer_interrupt+0xac/0x228 [] arch_timer_handler_phys+0x3c/0x50 [] handle_percpu_devid_irq+0x8c/0x290 [] generic_handle_irq+0x34/0x50 [] __handle_domain_irq+0x68/0xc0 [] gic_handle_irq+0x5c/0xb0 Fix this by dropping the ref-count decrement in unmap_and_move_hugepage() when !hugepage_migration_supported(). Fixes: 32665f2bbfed ("mm/migrate: correct failure handling if !hugepage_migration_support()") Reported-by: Manoj Iyer Signed-off-by: Punit Agrawal Cc: Joonsoo Kim Cc: Naoya Horiguchi Cc: Wanpeng Li Cc: Christoph Lameter -- Hi Andrew, We ran into this bug when working towards enabling memory corruption on arm64. The patch was tested on an arm64 platform running v4.12-rc2 with the series to enable memory corruption handling[0]. Please consider merging as a fix for the 4.12 release. Thanks, Punit [0] https://www.spinics.net/lists/arm-kernel/msg581657.html --- mm/migrate.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/mm/migrate.c b/mm/migrate.c index 89a0a1707f4c..187abd1526df 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1201,10 +1201,8 @@ static int unmap_and_move_huge_page(new_page_t get_new_page, * tables or check whether the hugepage is pmd-based or not before * kicking migration. */ - if (!hugepage_migration_supported(page_hstate(hpage))) { - putback_active_hugepage(hpage); + if (!hugepage_migration_supported(page_hstate(hpage))) return -ENOSYS; - } new_hpage = get_new_page(hpage, private, &result); if (!new_hpage) -- 2.11.0 -- 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