From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f173.google.com (mail-wi0-f173.google.com [209.85.212.173]) by kanga.kvack.org (Postfix) with ESMTP id CFD6B6B0032 for ; Wed, 11 Feb 2015 15:30:40 -0500 (EST) Received: by mail-wi0-f173.google.com with SMTP id bs8so23346294wib.0 for ; Wed, 11 Feb 2015 12:30:40 -0800 (PST) Received: from mail-wg0-x22d.google.com (mail-wg0-x22d.google.com. [2a00:1450:400c:c00::22d]) by mx.google.com with ESMTPS id vv8si844918wjc.96.2015.02.11.12.30.37 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 11 Feb 2015 12:30:38 -0800 (PST) Received: by mail-wg0-f45.google.com with SMTP id k14so2808467wgh.4 for ; Wed, 11 Feb 2015 12:30:37 -0800 (PST) Date: Wed, 11 Feb 2015 12:30:30 -0800 (PST) From: David Rientjes Subject: Re: [PATCH 0/3] memory_hotplug: hyperv: fix deadlock between memory adding and onlining In-Reply-To: <1423669462-30918-1-git-send-email-vkuznets@redhat.com> Message-ID: References: <1423669462-30918-1-git-send-email-vkuznets@redhat.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Vitaly Kuznetsov Cc: Greg Kroah-Hartman , "K. Y. Srinivasan" , Haiyang Zhang , Andrew Morton , Yasuaki Ishimatsu , Tang Chen , Vlastimil Babka , Fabian Frederick , Zhang Zhen , Vladimir Davydov , Wang Nan , linux-kernel@vger.kernel.org, devel@linuxdriverproject.org, linux-mm@kvack.org On Wed, 11 Feb 2015, Vitaly Kuznetsov wrote: > If newly added memory is brought online with e.g. udev rule: > SUBSYSTEM=="memory", ACTION=="add", ATTR{state}="online" > the following deadlock is observed (and easily reproducable): > > First participant, worker thread doing add_memory(): > > [ 724.948846] kworker/0:1 D ffff88000412f9c8 13248 27 2 0x00000000 > [ 724.973543] Workqueue: events hot_add_req [hv_balloon] > [ 724.991736] ffff88000412f9c8 0000000000000000 ffff88003fa1dc30 00000000000151c0 > [ 725.019725] 0000000000000246 ffff88000412ffd8 00000000000151c0 ffff88003a77a4e0 > [ 725.046486] ffff88003fa1dc30 00000001032a6000 ffff88003a7ca838 ffff88003a7ca898 > [ 725.072969] Call Trace: > [ 725.082690] [] schedule_preempt_disabled+0x29/0x70 > [ 725.103799] [] mutex_lock_nested+0x14b/0x470 > [ 725.122367] [] ? device_attach+0x23/0xb0 > [ 725.140992] [] device_attach+0x23/0xb0 > [ 725.159131] [] bus_probe_device+0xb0/0xe0 > [ 725.177055] [] device_add+0x443/0x650 > [ 725.195558] [] device_register+0x1e/0x30 > [ 725.213133] [] init_memory_block+0xd0/0xf0 > [ 725.231533] [] register_new_memory+0xb1/0xd0 > [ 725.250769] [] __add_pages+0x13f/0x250 > [ 725.269642] [] ? arch_add_memory+0x70/0xf0 > [ 725.288764] [] arch_add_memory+0x70/0xf0 > [ 725.306117] [] add_memory+0xef/0x1f0 > [ 725.322466] [] hot_add_req+0x33f/0xf90 [hv_balloon] > [ 725.342777] [] process_one_work+0x1df/0x4e0 > [ 725.361459] [] ? process_one_work+0x16d/0x4e0 > [ 725.380390] [] worker_thread+0x11b/0x450 > [ 725.397684] [] ? process_one_work+0x4e0/0x4e0 > [ 725.416533] [] kthread+0xf3/0x110 > [ 725.433372] [] ? kthread_create_on_node+0x240/0x240 > [ 725.453749] [] ret_from_fork+0x7c/0xb0 > [ 725.470994] [] ? kthread_create_on_node+0x240/0x240 > [ 725.491469] 6 locks held by kworker/0:1/27: > [ 725.505037] #0: ("events"){......}, at: [] process_one_work+0x16d/0x4e0 > [ 725.533370] #1: ((&dm_device.ha_wrk.wrk)){......}, at: [] process_one_work+0x16d/0x4e0 > [ 725.565580] #2: (mem_hotplug.lock){......}, at: [] mem_hotplug_begin+0x5/0x80 > [ 725.594369] #3: (mem_hotplug.lock#2){......}, at: [] mem_hotplug_begin+0x4f/0x80 > [ 725.628554] #4: (mem_sysfs_mutex){......}, at: [] register_new_memory+0x33/0xd0 > [ 725.658519] #5: (&dev->mutex){......}, at: [] device_attach+0x23/0xb0 > > Second participant, udev: > > [ 725.750889] systemd-udevd D ffff88003b94fc68 14016 888 530 0x00000004 > [ 725.773767] ffff88003b94fc68 0000000000000000 ffff8800034949c0 00000000000151c0 > [ 725.798332] ffffffff8210d980 ffff88003b94ffd8 00000000000151c0 ffff880037a69270 > [ 725.822841] ffff8800034949c0 0000000100000001 ffff8800034949c0 ffffffff81ff2b48 > [ 725.849184] Call Trace: > [ 725.858987] [] schedule_preempt_disabled+0x29/0x70 > [ 725.879231] [] mutex_lock_nested+0x14b/0x470 > [ 725.897860] [] ? mem_hotplug_begin+0x4f/0x80 > [ 725.916698] [] mem_hotplug_begin+0x4f/0x80 > [ 725.935064] [] ? mem_hotplug_begin+0x5/0x80 > [ 725.953464] [] online_pages+0x3b/0x520 > [ 725.971542] [] ? device_online+0x23/0xa0 > [ 725.989207] [] memory_subsys_online+0x64/0xc0 > [ 726.008513] [] device_online+0x6d/0xa0 > [ 726.025579] [] store_mem_state+0x5b/0xe0 > [ 726.043400] [] dev_attr_store+0x18/0x30 > [ 726.060506] [] sysfs_kf_write+0x48/0x60 > [ 726.077940] [] kernfs_fop_write+0x13b/0x1a0 > [ 726.099416] [] vfs_write+0xb7/0x1f0 > [ 726.115748] [] SyS_write+0x58/0xd0 > [ 726.131933] [] system_call_fastpath+0x12/0x17 > [ 726.150691] 7 locks held by systemd-udevd/888: > [ 726.165044] #0: (sb_writers#3){......}, at: [] vfs_write+0x1b3/0x1f0 > [ 726.192422] #1: (&of->mutex){......}, at: [] kernfs_fop_write+0x66/0x1a0 > [ 726.220289] #2: (s_active#60){......}, at: [] kernfs_fop_write+0x6e/0x1a0 > [ 726.249382] #3: (device_hotplug_lock){......}, at: [] lock_device_hotplug_sysfs+0x15/0x50 > [ 726.281901] #4: (&dev->mutex){......}, at: [] device_online+0x23/0xa0 > [ 726.308619] #5: (mem_hotplug.lock){......}, at: [] mem_hotplug_begin+0x5/0x80 > [ 726.337994] #6: (mem_hotplug.lock#2){......}, at: [] mem_hotplug_begin+0x4f/0x80 > > In short: onlining grabs device lock and then tries to do mem_hotplug_begin() > while add_memory() is between mem_hotplug_begin() and mem_hotplug_done() and it > tries grabbing device lock. > > To my understanding ACPI memory hotplug doesn't have the same issue as > device_hotplug_lock is being grabbed when the ACPI device is added. > > Solve the issue by grabbing device_hotplug_lock before doing add_memory(). If > we do that, lock_device_hotplug_sysfs() will cause syscall retry which will > eventually succeed. To support the change we need to export lock_device_hotplug/ > unlock_device_hotplug. This approach can be completely wrong though. Saying the approach could be completely wrong doesn't inspire a lot of confidence. I assume this output is from the hung task detector, is there any other lockdep output that suggests there's a possible deadlock? -- 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