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Message-ID: <BY2PR0301MB071121896C2C9A93BD7E665BA0220@BY2PR0301MB0711.namprd03.prod.outlook.com>
Date: Thu, 12 Feb 2015 17:40:44 +0000
From: KY Srinivasan <kys@...rosoft.com>
To: Vitaly Kuznetsov <vkuznets@...hat.com>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
Haiyang Zhang <haiyangz@...rosoft.com>,
Andrew Morton <akpm@...ux-foundation.org>,
"Yasuaki Ishimatsu" <isimatu.yasuaki@...fujitsu.com>,
Tang Chen <tangchen@...fujitsu.com>,
Vlastimil Babka <vbabka@...e.cz>,
David Rientjes <rientjes@...gle.com>,
Fabian Frederick <fabf@...net.be>,
Zhang Zhen <zhenzhang.zhang@...wei.com>,
Vladimir Davydov <vdavydov@...allels.com>,
"Wang Nan" <wangnan0@...wei.com>,
"Rafael J. Wysocki" <rjw@...ysocki.net>,
"devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: RE: [PATCH RESEND 0/3] memory_hotplug: hyperv: fix deadlock between
memory adding and onlining
> -----Original Message-----
> From: Vitaly Kuznetsov [mailto:vkuznets@...hat.com]
> Sent: Thursday, February 12, 2015 7:50 AM
> To: KY Srinivasan
> Cc: linux-kernel@...r.kernel.org; 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@...uxdriverproject.org; linux-mm@...ck.org
> Subject: Re: [PATCH RESEND 0/3] memory_hotplug: hyperv: fix deadlock
> between memory adding and onlining
>
> KY Srinivasan <kys@...rosoft.com> writes:
>
> >> -----Original Message-----
> >> From: Vitaly Kuznetsov [mailto:vkuznets@...hat.com]
> >> Sent: Thursday, February 12, 2015 2:24 AM
> >> To: linux-kernel@...r.kernel.org
> >> 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@...uxdriverproject.org; linux-mm@...ck.org
> >> 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
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