From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from outbound-smtp06.blacknight.com ([81.17.249.39]:43149 "EHLO outbound-smtp06.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750820AbdEZKsM (ORCPT ); Fri, 26 May 2017 06:48:12 -0400 Received: from mail.blacknight.com (pemlinmail06.blacknight.ie [81.17.255.152]) by outbound-smtp06.blacknight.com (Postfix) with ESMTPS id 36F0498920 for ; Fri, 26 May 2017 10:42:44 +0000 (UTC) Date: Fri, 26 May 2017 11:42:39 +0100 From: Mel Gorman To: akpm@linux-foundation.org Cc: punit.agrawal@arm.com, cl@linux.com, iamjoonsoo.kim@lge.com, manoj.iyer@canonical.com, n-horiguchi@ah.jp.nec.com, stable@vger.kernel.org, wanpeng.li@hotmail.com, mm-commits@vger.kernel.org Subject: Re: + mm-migrate-fix-ref-count-handling-when-hugepage_migration_supported-v2.patch added to -mm tree Message-ID: <20170526104239.d2dwmm3vdcjx2g5n@techsingularity.net> References: <59275ebf.J2Z9kk9uuHWKdJS8%akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <59275ebf.J2Z9kk9uuHWKdJS8%akpm@linux-foundation.org> Sender: stable-owner@vger.kernel.org List-ID: On Thu, May 25, 2017 at 03:46:23PM -0700, akpm@linux-foundation.org wrote: > ------------------------------------------------------ > From: Punit Agrawal > Subject: mm/migrate: fix refcount handling when !hugepage_migration_supported() > > 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 > > Address this by changing the putback_active_hugepage() in > soft_offline_huge_page() to putback_movable_pages(). > I've never looked too closely at how hardware poisoning and hugetlb pages migration is handled so I could easily have missed something but this changelog and patch confuses me. Surely if the inconsistency is between hugepage_migration_supported and !hugepage_migration_supported then the check in soft_offline_huge_page() should also be related to hugepage_migration_supported either in soft_offline_huge_page() or in putback_movable_pages()? -- Mel Gorman SUSE Labs