From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f198.google.com (mail-pf0-f198.google.com [209.85.192.198]) by kanga.kvack.org (Postfix) with ESMTP id 255EF6B0279 for ; Wed, 24 May 2017 22:11:57 -0400 (EDT) Received: by mail-pf0-f198.google.com with SMTP id b74so211976102pfd.2 for ; Wed, 24 May 2017 19:11:57 -0700 (PDT) Received: from tyo161.gate.nec.co.jp (tyo161.gate.nec.co.jp. [114.179.232.161]) by mx.google.com with ESMTPS id z69si26255636pfk.418.2017.05.24.19.11.55 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 24 May 2017 19:11:56 -0700 (PDT) From: Naoya Horiguchi Subject: Re: [PATCH] mm/migrate: Fix ref-count handling when !hugepage_migration_supported() Date: Thu, 25 May 2017 01:59:28 +0000 Message-ID: <20170525015927.GA26520@hori1.linux.bs1.fc.nec.co.jp> References: <20170524154728.2492-1-punit.agrawal@arm.com> In-Reply-To: <20170524154728.2492-1-punit.agrawal@arm.com> Content-Language: ja-JP Content-Type: text/plain; charset="iso-2022-jp" Content-ID: Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Sender: owner-linux-mm@kvack.org List-ID: To: Punit Agrawal Cc: Andrew Morton , "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 , Wanpeng Li , Christoph Lameter On Wed, May 24, 2017 at 04:47:28PM +0100, Punit Agrawal wrote: > 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. >=20 > This leads to soft lockups when running the overcommitted hugepage test > from mce-tests suite. >=20 > 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=3D5254 jiffies, g=3D963, c=3D962, q=3D321) > 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 >=20 > Fix this by dropping the ref-count decrement in > unmap_and_move_hugepage() when !hugepage_migration_supported(). >=20 > Fixes: 32665f2bbfed ("mm/migrate: correct failure handling if !hugepage_m= igration_support()") > Reported-by: Manoj Iyer > Signed-off-by: Punit Agrawal > Cc: Joonsoo Kim > Cc: Naoya Horiguchi > Cc: Wanpeng Li > Cc: Christoph Lameter >=20 > -- > Hi Andrew, >=20 > 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]. >=20 > Please consider merging as a fix for the 4.12 release. >=20 > Thanks, > Punit >=20 > [0] https://www.spinics.net/lists/arm-kernel/msg581657.html > --- > mm/migrate.c | 4 +--- > 1 file changed, 1 insertion(+), 3 deletions(-) >=20 > 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); Thank you for reporting and suggestion, Punit, Manoj. Simply dropping this putback_active_hugepage() may resume the failure counting issue addressed in 32665f2bbfed, so I would recommend to call putback_movable_pages() in failure path in soft_offline_huge_page(). @@ -1600,7 +1600,8 @@ static int soft_offline_huge_page(struct page *page, = int flags) * only one hugepage pointed to by hpage, so we need not * run through the pagelist here. */ - putback_active_hugepage(hpage); + if (!list_empty(&pagelist)) + putback_movable_pages(&pagelist); if (ret > 0) ret =3D -EIO; } else { Could you check this works for you? Thanks, Naoya Horiguchi= -- 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