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 8265C6B0292 for ; Wed, 24 May 2017 22:13:01 -0400 (EDT) Received: by mail-pf0-f198.google.com with SMTP id e7so205596649pfk.9 for ; Wed, 24 May 2017 19:13:01 -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 x7si26274611pff.280.2017.05.24.19.13.00 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 24 May 2017 19:13:00 -0700 (PDT) From: Naoya Horiguchi Subject: Re: [PATCH] mm/migrate: Fix ref-count handling when !hugepage_migration_supported() Date: Thu, 25 May 2017 02:11:43 +0000 Message-ID: <20170525021142.GB26520@hori1.linux.bs1.fc.nec.co.jp> References: <20170524154728.2492-1-punit.agrawal@arm.com> <20170524125610.8fbc644f8fa1cf8175b7757b@linux-foundation.org> In-Reply-To: <20170524125610.8fbc644f8fa1cf8175b7757b@linux-foundation.org> Content-Language: ja-JP Content-Type: text/plain; charset="iso-2022-jp" Content-ID: <3BB02A997C24BB429E89A0CCE36B595D@gisp.nec.co.jp> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 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 , Wanpeng Li , Christoph Lameter On Wed, May 24, 2017 at 12:56:10PM -0700, Andrew Morton wrote: > On Wed, 24 May 2017 16:47:28 +0100 Punit Agrawal = wrote: >=20 > > 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= _migration_support()") > > Reported-by: Manoj Iyer > > Signed-off-by: Punit Agrawal > > Cc: Joonsoo Kim > > Cc: Naoya Horiguchi > > Cc: Wanpeng Li > > Cc: Christoph Lameter >=20 > 32665f2bbfed was three years ago. Do you have any theory as to why > this took so long to be detected? My per-release testing only ran for "hugepage_migration_supported() =3D=3D = true" setting (i.e. x86 with CONFIG_HUGETLB_PAGE=3Dy). I need extend the coverage= . And other arch's developers recently have come to have interest in hugepage migration. > And do you believe a -stable > backport is warranted? I agree to send the fix to stable, so the stable tag is wanted. Cc: stable@kernel.org # v3.14+ 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