KY Srinivasan <kys@xxxxxxxxxxxxx> writes: >> -----Original Message----- >> From: Vitaly Kuznetsov [mailto:vkuznets@xxxxxxxxxx] >> Sent: Thursday, February 12, 2015 2:24 AM >> To: linux-kernel@xxxxxxxxxxxxxxx >> Cc: Greg Kroah-Hartman; KY Srinivasan; Haiyang Zhang; Andrew Morton; >> Yasuaki Ishimatsu; Tang Chen; Vlastimil Babka; David Rientjes; Fabian >> Frederick; Zhang Zhen; Vladimir Davydov; Wang Nan; Rafael J. Wysocki; >> devel@xxxxxxxxxxxxxxxxxxxxxx; linux-mm@xxxxxxxxx >> Subject: [PATCH RESEND 0/3] memory_hotplug: hyperv: fix deadlock >> between memory adding and onlining >> >> RESEND (with no changes) because Rafael J. Wysocki was missing in >> recepients. >> >> 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] [<ffffffff81aac0a9>] schedule_preempt_disabled+0x29/0x70 >> [ 725.103799] [<ffffffff81aae33b>] mutex_lock_nested+0x14b/0x470 [ >> 725.122367] [<ffffffff815ed773>] ? device_attach+0x23/0xb0 [ 725.140992] >> [<ffffffff815ed773>] device_attach+0x23/0xb0 [ 725.159131] >> [<ffffffff815ecba0>] bus_probe_device+0xb0/0xe0 [ 725.177055] >> [<ffffffff815ea693>] device_add+0x443/0x650 [ 725.195558] >> [<ffffffff815ea8be>] device_register+0x1e/0x30 [ 725.213133] >> [<ffffffff81601790>] init_memory_block+0xd0/0xf0 [ 725.231533] >> [<ffffffff816018f1>] register_new_memory+0xb1/0xd0 [ 725.250769] >> [<ffffffff81a961cf>] __add_pages+0x13f/0x250 [ 725.269642] >> [<ffffffff81063770>] ? arch_add_memory+0x70/0xf0 [ 725.288764] >> [<ffffffff81063770>] arch_add_memory+0x70/0xf0 [ 725.306117] >> [<ffffffff81a95f8f>] add_memory+0xef/0x1f0 [ 725.322466] >> [<ffffffffa00293af>] hot_add_req+0x33f/0xf90 [hv_balloon] [ 725.342777] >> [<ffffffff8109509f>] process_one_work+0x1df/0x4e0 [ 725.361459] >> [<ffffffff8109502d>] ? process_one_work+0x16d/0x4e0 [ 725.380390] >> [<ffffffff810954bb>] worker_thread+0x11b/0x450 [ 725.397684] >> [<ffffffff810953a0>] ? process_one_work+0x4e0/0x4e0 [ 725.416533] >> [<ffffffff8109ac33>] kthread+0xf3/0x110 [ 725.433372] [<ffffffff8109ab40>] >> ? kthread_create_on_node+0x240/0x240 >> [ 725.453749] [<ffffffff81ab1dfc>] ret_from_fork+0x7c/0xb0 [ 725.470994] >> [<ffffffff8109ab40>] ? kthread_create_on_node+0x240/0x240 >> [ 725.491469] 6 locks held by kworker/0:1/27: >> [ 725.505037] #0: ("events"){......}, at: [<ffffffff8109502d>] >> process_one_work+0x16d/0x4e0 [ 725.533370] #1: >> ((&dm_device.ha_wrk.wrk)){......}, at: [<ffffffff8109502d>] >> process_one_work+0x16d/0x4e0 [ 725.565580] #2: >> (mem_hotplug.lock){......}, at: [<ffffffff811e6525>] >> mem_hotplug_begin+0x5/0x80 [ 725.594369] #3: >> (mem_hotplug.lock#2){......}, at: [<ffffffff811e656f>] >> mem_hotplug_begin+0x4f/0x80 [ 725.628554] #4: >> (mem_sysfs_mutex){......}, at: [<ffffffff81601873>] >> register_new_memory+0x33/0xd0 [ 725.658519] #5: (&dev->mutex){......}, >> at: [<ffffffff815ed773>] 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] [<ffffffff81aac0a9>] schedule_preempt_disabled+0x29/0x70 >> [ 725.879231] [<ffffffff81aae33b>] mutex_lock_nested+0x14b/0x470 [ >> 725.897860] [<ffffffff811e656f>] ? mem_hotplug_begin+0x4f/0x80 [ >> 725.916698] [<ffffffff811e656f>] mem_hotplug_begin+0x4f/0x80 [ >> 725.935064] [<ffffffff811e6525>] ? mem_hotplug_begin+0x5/0x80 [ >> 725.953464] [<ffffffff81a9631b>] online_pages+0x3b/0x520 [ 725.971542] >> [<ffffffff815eb0b3>] ? device_online+0x23/0xa0 [ 725.989207] >> [<ffffffff81601524>] memory_subsys_online+0x64/0xc0 [ 726.008513] >> [<ffffffff815eb0fd>] device_online+0x6d/0xa0 [ 726.025579] >> [<ffffffff816012eb>] store_mem_state+0x5b/0xe0 [ 726.043400] >> [<ffffffff815e8258>] dev_attr_store+0x18/0x30 [ 726.060506] >> [<ffffffff8127a808>] sysfs_kf_write+0x48/0x60 [ 726.077940] >> [<ffffffff81279d1b>] kernfs_fop_write+0x13b/0x1a0 [ 726.099416] >> [<ffffffff811f9f67>] vfs_write+0xb7/0x1f0 [ 726.115748] [<ffffffff811fabf8>] >> SyS_write+0x58/0xd0 [ 726.131933] [<ffffffff81ab1ea9>] >> system_call_fastpath+0x12/0x17 [ 726.150691] 7 locks held by systemd- >> udevd/888: >> [ 726.165044] #0: (sb_writers#3){......}, at: [<ffffffff811fa063>] >> vfs_write+0x1b3/0x1f0 [ 726.192422] #1: (&of->mutex){......}, at: >> [<ffffffff81279c46>] kernfs_fop_write+0x66/0x1a0 [ 726.220289] #2: >> (s_active#60){......}, at: [<ffffffff81279c4e>] kernfs_fop_write+0x6e/0x1a0 [ >> 726.249382] #3: (device_hotplug_lock){......}, at: [<ffffffff815e9c15>] >> lock_device_hotplug_sysfs+0x15/0x50 >> [ 726.281901] #4: (&dev->mutex){......}, at: [<ffffffff815eb0b3>] >> device_online+0x23/0xa0 [ 726.308619] #5: (mem_hotplug.lock){......}, at: >> [<ffffffff811e6525>] mem_hotplug_begin+0x5/0x80 [ 726.337994] #6: >> (mem_hotplug.lock#2){......}, at: [<ffffffff811e656f>] >> 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. > > This issue was first discovered by Andy Whitcroft: https://lkml.org/lkml/2014/3/14/451 > I had sent patches based on Andy's analysis that did not affect the users of the kernel hot-add > memory APIs: https://lkml.org/lkml/2014/12/2/662 Sorry I missed that. > > This patch puts the burden where it needs to be and can address the issue for all clients. > There is also one good solution from David Rientjes: https://lkml.org/lkml/2015/2/12/57 I just tested it and it also solves the issue. > K. Y >> >> Vitaly Kuznetsov (3): >> driver core: export lock_device_hotplug/unlock_device_hotplug >> memory_hotplug: add note about holding device_hotplug_lock and >> add_memory() >> Drivers: hv: balloon: fix deadlock between memory adding and onlining >> >> drivers/base/core.c | 2 ++ >> drivers/hv/hv_balloon.c | 10 ++++++++++ >> mm/memory_hotplug.c | 6 +++++- >> 3 files changed, 17 insertions(+), 1 deletion(-) >> >> -- >> 1.9.3 -- Vitaly -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>