From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f200.google.com (mail-wr0-f200.google.com [209.85.128.200]) by kanga.kvack.org (Postfix) with ESMTP id 5C8866B039F for ; Wed, 26 Jul 2017 09:34:36 -0400 (EDT) Received: by mail-wr0-f200.google.com with SMTP id w63so31866225wrc.5 for ; Wed, 26 Jul 2017 06:34:36 -0700 (PDT) Received: from Galois.linutronix.de (Galois.linutronix.de. [2a01:7a0:2:106d:700::1]) by mx.google.com with ESMTPS id u135si1307wmd.240.2017.07.26.06.34.35 for (version=TLS1_2 cipher=AES128-SHA bits=128/128); Wed, 26 Jul 2017 06:34:35 -0700 (PDT) Date: Wed, 26 Jul 2017 15:34:31 +0200 (CEST) From: Thomas Gleixner Subject: Re: [PATCH] mm: take memory hotplug lock within numa_zonelist_order_handler() In-Reply-To: <20170726111738.38768-1-heiko.carstens@de.ibm.com> Message-ID: References: <20170726111738.38768-1-heiko.carstens@de.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Heiko Carstens Cc: Andrew Morton , linux-mm@kvack.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, Andre Wild , KAMEZAWA Hiroyuki , Michal Hocko , Vlastimil Babka On Wed, 26 Jul 2017, Heiko Carstens wrote: > Andre Wild reported the folling warning: > > WARNING: CPU: 2 PID: 1205 at kernel/cpu.c:240 lockdep_assert_cpus_held+0x4c/0x60 > Modules linked in: > CPU: 2 PID: 1205 Comm: bash Not tainted 4.13.0-rc2-00022-gfd2b2c57ec20 #10 > Hardware name: IBM 2964 N96 702 (z/VM 6.4.0) > task: 00000000701d8100 task.stack: 0000000073594000 > Krnl PSW : 0704f00180000000 0000000000145e24 (lockdep_assert_cpus_held+0x4c/0x60) > ... > Call Trace: > lockdep_assert_cpus_held+0x42/0x60) > stop_machine_cpuslocked+0x62/0xf0 > build_all_zonelists+0x92/0x150 > numa_zonelist_order_handler+0x102/0x150 > proc_sys_call_handler.isra.12+0xda/0x118 > proc_sys_write+0x34/0x48 > __vfs_write+0x3c/0x178 > vfs_write+0xbc/0x1a0 > SyS_write+0x66/0xc0 > system_call+0xc4/0x2b0 > locks held by bash/1205: > #0: (sb_writers#4){.+.+.+}, at: [<000000000037b29e>] vfs_write+0xa6/0x1a0 > #1: (zl_order_mutex){+.+...}, at: [<00000000002c8e4c>] numa_zonelist_order_handler+0x44/0x150 > #2: (zonelists_mutex){+.+...}, at: [<00000000002c8efc>] numa_zonelist_order_handler+0xf4/0x150 > Last Breaking-Event-Address: > [<0000000000145e20>] lockdep_assert_cpus_held+0x48/0x60 > > This can be easily triggered with e.g. > > >echo n > /proc/sys/vm/numa_zonelist_order > > With commit 3f906ba23689a ("mm/memory-hotplug: switch locking to a > percpu rwsem") memory hotplug locking was changed to fix a potential > deadlock. This also switched the stop_machine() invocation within > build_all_zonelists() to stop_machine_cpuslocked() which now expects > that online cpus are locked when being called. > > This assumption is not true if build_all_zonelists() is being called > from numa_zonelist_order_handler(). In order to fix this simply add a > mem_hotplug_begin()/mem_hotplug_done() pair to numa_zonelist_order_handler(). Sorry, I missed that call path when I did the conversion. So yes, that needs some protection.... Thanks, tglx -- 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