> -----Original Message----- > From: Vitaly Kuznetsov [mailto:vkuznets@xxxxxxxxxx] > Sent: Thursday, February 12, 2015 7:50 AM > To: KY Srinivasan > Cc: linux-kernel@xxxxxxxxxxxxxxx; Greg Kroah-Hartman; 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: Re: [PATCH RESEND 0/3] memory_hotplug: hyperv: fix deadlock > between memory adding and onlining > > 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. Thanks; looks good. K. Y > > > > 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 _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
