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 78BFE6B0279 for ; Wed, 24 May 2017 15:56:14 -0400 (EDT) Received: by mail-pf0-f198.google.com with SMTP id b74so201715931pfd.2 for ; Wed, 24 May 2017 12:56:14 -0700 (PDT) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTPS id b78si25161507pfe.220.2017.05.24.12.56.13 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 24 May 2017 12:56:13 -0700 (PDT) Date: Wed, 24 May 2017 12:56:10 -0700 From: Andrew Morton Subject: Re: [PATCH] mm/migrate: Fix ref-count handling when !hugepage_migration_supported() Message-Id: <20170524125610.8fbc644f8fa1cf8175b7757b@linux-foundation.org> In-Reply-To: <20170524154728.2492-1-punit.agrawal@arm.com> References: <20170524154728.2492-1-punit.agrawal@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Punit Agrawal Cc: 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 Wed, 24 May 2017 16:47:28 +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. > > 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 32665f2bbfed was three years ago. Do you have any theory as to why this took so long to be detected? And do you believe a -stable backport is warranted? -- 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