Date:	Mon, 24 Feb 2014 11:13:15 -0500
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Steven Noonan <steven@...inklabs.net>,
	kosaki.motohiro@...fujitsu.com, mgorman@...e.de
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Subject: Is: 'mm: __set_page_dirty_nobuffers() uses spin_lock_irqsave()
 instead of spin_lock_irq()' fixed it.Was:Re: [BISECTED] Xen HVM guest hangs
 since 3.12-rc5

On Sat, Feb 22, 2014 at 11:53:31PM -0800, Steven Noonan wrote:
> On Fri, Feb 21, 2014 at 12:07 PM, Konrad Rzeszutek Wilk
> <konrad.wilk@...cle.com> wrote:
> > On Thu, Feb 20, 2014 at 12:44:15PM -0800, Steven Noonan wrote:
> >> On Wed, Feb 19, 2014 at 1:01 PM, Steven Noonan <steven@...inklabs.net> wrote:
> >> > On Wed, Feb 19, 2014 at 9:41 AM, Konrad Rzeszutek Wilk
> >> > <konrad.wilk@...cle.com> wrote:
> >> >> On Tue, Feb 18, 2014 at 11:16:05PM -0800, Steven Noonan wrote:
> >> >>> I've been running into problems on an Xen HVM domU. I've got a guest with NUMA
> >> >>> enabled, 60GB of RAM, and 3 disks attached (including root volume). 2 of the
> >> >>> disks are in an MD RAID0 in the guest, with an ext4 filesystem on top of that.
> >> >>> I was running the fio 'iometer-file-access-server.fio' example config against
> >> >>> that fs. During this workload, it would eventually cause a soft lockup, like
> >> >>> the below:
> >> >>
> >> >> I presume since you mention NUMA and Mel is CC-ed that if you boot without
> >> >> NUMA enabled (either via the toolstack or via Linux command line) - the issue
> >> >> is not present?
> >> >
> >> > I mentioned NUMA because the bisected commit is sched/numa, and the
> >> > guest is NUMA-enabled. I hadn't attempted booting with NUMA off. I
> >> > just tried with numa=off, and the workload has run in a loop for 20
> >> > minutes so far with no issues (normally the issue would repro in less
> >> > than 5).
> >>
> >> The subject line is actually incorrect -- I did a 'git describe' on
> >> the result of the bisection when writing the subject line, but the
> >> '3.12-rc5' tag was just the base on which the code was originally
> >> developed. As far as what tags actually contain the commit:
> >>
> >> $ git tag --contains b795854b1fa70f6aee923ae5df74ff7afeaddcaa
> >> v3.13
> >> v3.13-rc1
> >> v3.13-rc2
> >> v3.13-rc3
> >> v3.13-rc4
> >> v3.13-rc5
> >> v3.13-rc6
> >> v3.13-rc7
> >> v3.13-rc8
> >> v3.13.1
> >> v3.13.2
> >> v3.13.3
> >> v3.14-rc1
> >> v3.14-rc2
> >>
> >> So it's more accurate to say it was introduced in the v3.13 merge window.
> >>
> >> In any case, does anyone have any ideas?
> >
> > There is nothing in that git commit that gives that 'AHA' feeling.
> >
> > If you revert that patch on top of the latest Linux kernel does the problem
> > go away? This is more of a double-check to see if the commit
> > is really the fault or if it exposed some latent issue.
> 
> I just tried out 3.13.5 and the problem went away. Looking through the
> commit logs, it appears this commit (added as part of 3.13.4) resolved
> the issue:

Excellent! Problem solved :-)

> 
> commit 27b4328e523b3de854229e6b505f94aa9708dde6
> Author: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> Date:   Thu Feb 6 12:04:24 2014 -0800
> 
>     mm: __set_page_dirty_nobuffers() uses spin_lock_irqsave() instead
> of spin_lock_irq()
> 
>     commit a85d9df1ea1d23682a0ed1e100e6965006595d06 upstream.
> 
>     During aio stress test, we observed the following lockdep warning.  This
>     mean AIO+numa_balancing is currently deadlockable.
> 
>     The problem is, aio_migratepage disable interrupt, but
>     __set_page_dirty_nobuffers unintentionally enable it again.
> 
>     Generally, all helper function should use spin_lock_irqsave() instead of
>     spin_lock_irq() because they don't know caller at all.
> 
>        other info that might help us debug this:
>         Possible unsafe locking scenario:
> 
>               CPU0
>               ----
>          lock(&(&ctx->completion_lock)->rlock);
>          <Interrupt>
>            lock(&(&ctx->completion_lock)->rlock);
> 
>         *** DEADLOCK ***
> 
>           dump_stack+0x19/0x1b
>           print_usage_bug+0x1f7/0x208
>           mark_lock+0x21d/0x2a0
>           mark_held_locks+0xb9/0x140
>           trace_hardirqs_on_caller+0x105/0x1d0
>           trace_hardirqs_on+0xd/0x10
>           _raw_spin_unlock_irq+0x2c/0x50
>           __set_page_dirty_nobuffers+0x8c/0xf0
>           migrate_page_copy+0x434/0x540
>           aio_migratepage+0xb1/0x140
>           move_to_new_page+0x7d/0x230
>           migrate_pages+0x5e5/0x700
>           migrate_misplaced_page+0xbc/0xf0
>           do_numa_page+0x102/0x190
>           handle_pte_fault+0x241/0x970
>           handle_mm_fault+0x265/0x370
>           __do_page_fault+0x172/0x5a0
>           do_page_fault+0x1a/0x70
>           page_fault+0x28/0x30
> 
>     Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
>     Cc: Larry Woodman <lwoodman@...hat.com>
>     Cc: Rik van Riel <riel@...hat.com>
>     Cc: Johannes Weiner <jweiner@...hat.com>
>     Acked-by: David Rientjes <rientjes@...gle.com>
>     Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
>     Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
>     Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> 
> >>
> >> >>>
> >> >>> [ 2536.250054] BUG: soft lockup - CPU#0 stuck for 23s! [kworker/u257:0:7]
> >> >>> [ 2536.250054] Modules linked in: isofs crct10dif_pclmul crct10dif_common crc32_pclmul crc32c_intel ghash_clmulni_intel aesni_intel aes_x86_64 lrw gf128mul glue_helper ablk_helper cryptd raid0 md_mod acpi_cpufreq psmouse i2c_piix4 intel_agp intel_gtt i2c_core processor serio_raw evdev microcode ext4 crc16 mbcache jbd2 ata_generic pata_acpi ata_piix libata scsi_mod floppy ixgbevf xen_privcmd xen_netfront xen_kbdfront syscopyarea sysfillrect sysimgblt fb_sys_fops xen_blkfront virtio_pci virtio_net virtio_blk virtio_ring virtio ipmi_poweroff ipmi_msghandler button
> >> >>> [ 2536.250054] CPU: 0 PID: 7 Comm: kworker/u257:0 Tainted: G        W    3.12.0-rc4-bisect-00073-g6fe6b2d #26
> >> >>> [ 2536.250054] Hardware name: Xen HVM domU, BIOS 4.2.amazon 01/14/2014
> >> >>> [ 2536.250054] Workqueue: writeback bdi_writeback_workfn (flush-202:0)
> >> >>> [ 2536.250054] task: ffff880766533400 ti: ffff88076652e000 task.ti: ffff88076652e000
> >> >>> [ 2536.250054] RIP: 0010:[<ffffffff810cc518>]  [<ffffffff810cc518>] smp_call_function_many+0x258/0x2b0
> >> >>> [ 2536.250054] RSP: 0018:ffff88076652f878  EFLAGS: 00000202
> >> >>> [ 2536.250054] RAX: 000000000000000f RBX: ffff88076652f808 RCX: ffff880ef0ef74a8
> >> >>> [ 2536.250054] RDX: 000000000000000f RSI: 0000000000000080 RDI: 0000000000000000
> >> >>> [ 2536.250054] RBP: ffff88076652f8c0 R08: ffff880771046c00 R09: ffff880770c008e0
> >> >>> [ 2536.250054] R10: 000000000000003e R11: 0000000000000210 R12: ffff88076652f7f0
> >> >>> [ 2536.250054] R13: ffffffff810b859e R14: ffff88076652f7e0 R15: ffffffff810b50e7
> >> >>> [ 2536.250054] FS:  0000000000000000(0000) GS:ffff880771600000(0000) knlGS:0000000000000000
> >> >>> [ 2536.250054] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> >> >>> [ 2536.250054] CR2: 00007f8752bea000 CR3: 0000000001a0d000 CR4: 00000000001406f0
> >> >>> [ 2536.250054] Stack:
> >> >>> [ 2536.250054]  0000000181275231 0000000000014d00 ffff88076652f8d0 ffffffff810564e0
> >> >>> [ 2536.250054]  ffff88076530b180 00007f0c8826a000 ffff880ed4d57700 ffff88076530b180
> >> >>> [ 2536.250054]  ffff880ed4cc6350 ffff88076652f8e8 ffffffff81056637 ffff88076530b180
> >> >>> [ 2536.250054] Call Trace:
> >> >>> [ 2536.250054]  [<ffffffff810564e0>] ? leave_mm+0x70/0x70
> >> >>> [ 2536.250054]  [<ffffffff81056637>] native_flush_tlb_others+0x37/0x40
> >> >>> [ 2536.250054]  [<ffffffff81056988>] flush_tlb_page+0x88/0x90
> >> >>> [ 2536.250054]  [<ffffffff8117bb94>] ptep_clear_flush+0x34/0x40
> >> >>> [ 2536.250054]  [<ffffffff81175b1e>] page_mkclean+0x12e/0x1d0
> >> >>> [ 2536.250054]  [<ffffffff8114aeeb>] clear_page_dirty_for_io+0x3b/0xe0
> >> >>> [ 2536.250054]  [<ffffffffa016fd52>] mpage_submit_page+0x52/0x80 [ext4]
> >> >>> [ 2536.250054]  [<ffffffffa016fe89>] mpage_process_page_bufs+0x109/0x140 [ext4]
> >> >>> [ 2536.250054]  [<ffffffffa01700d7>] mpage_prepare_extent_to_map+0x217/0x2d0 [ext4]
> >> >>> [ 2536.250054]  [<ffffffffa0174929>] ext4_writepages+0x469/0xca0 [ext4]
> >> >>> [ 2536.250054]  [<ffffffff8114cd3e>] do_writepages+0x1e/0x50
> >> >>> [ 2536.250054]  [<ffffffff811d7716>] __writeback_single_inode+0x76/0x240
> >> >>> [ 2536.250054]  [<ffffffff811d7c12>] writeback_sb_inodes+0x282/0x420
> >> >>> [ 2536.250054]  [<ffffffff811d7e2f>] __writeback_inodes_wb+0x7f/0xd0
> >> >>> [ 2536.250054]  [<ffffffff811d884b>] wb_writeback+0x15b/0x2a0
> >> >>> [ 2536.250054]  [<ffffffff811d8fa7>] bdi_writeback_workfn+0x1d7/0x450
> >> >>> [ 2536.250054]  [<ffffffff8107be4d>] process_one_work+0x25d/0x460
> >> >>> [ 2536.250054]  [<ffffffff8107d196>] worker_thread+0x266/0x480
> >> >>> [ 2536.250054]  [<ffffffff8107cf30>] ? manage_workers.isra.18+0x3f0/0x3f0
> >> >>> [ 2536.250054]  [<ffffffff81083bcb>] kthread+0xbb/0xd0
> >> >>> [ 2536.250054]  [<ffffffff81083b10>] ? kthread_stop+0xf0/0xf0
> >> >>> [ 2536.250054]  [<ffffffff814d4dbc>] ret_from_fork+0x7c/0xb0
> >> >>> [ 2536.250054]  [<ffffffff81083b10>] ? kthread_stop+0xf0/0xf0
> >> >>> [ 2536.250054] Code: 00 74 70 48 63 35 d1 1f a1 00 ba ff ff ff ff eb 29 66 90 48 98 48 8b 0b 48 03 0c c5 00 27 ad 81 f6 41 20 01 74 14 0f 1f 44 00 00 <f3> 90 f6 41 20 01 75 f8 48 63 35 a1 1f a1 00 48 8b 7b 08 83 c2
> >> >>> [ 2544.900055] BUG: soft lockup - CPU#31 stuck for 24s! [systemd-journal:304]
> >> >>> [ 2544.900055] Modules linked in: isofs crct10dif_pclmul crct10dif_common crc32_pclmul crc32c_intel ghash_clmulni_intel aesni_intel aes_x86_64 lrw gf128mul glue_helper ablk_helper cryptd raid0 md_mod acpi_cpufreq psmouse i2c_piix4 intel_agp intel_gtt i2c_core processor serio_raw evdev microcode ext4 crc16 mbcache jbd2 ata_generic pata_acpi ata_piix libata scsi_mod floppy ixgbevf xen_privcmd xen_netfront xen_kbdfront syscopyarea sysfillrect sysimgblt fb_sys_fops xen_blkfront virtio_pci virtio_net virtio_blk virtio_ring virtio ipmi_poweroff ipmi_msghandler button
> >> >>> [ 2544.900055] CPU: 31 PID: 304 Comm: systemd-journal Tainted: G        W    3.12.0-rc4-bisect-00073-g6fe6b2d #26
> >> >>> [ 2544.900055] Hardware name: Xen HVM domU, BIOS 4.2.amazon 01/14/2014
> >> >>> [ 2544.900055] task: ffff880764bcb400 ti: ffff8807653f6000 task.ti: ffff8807653f6000
> >> >>> [ 2544.900055] RIP: 0010:[<ffffffff810cc040>]  [<ffffffff810cc040>] generic_exec_single+0x80/0xa0
> >> >>> [ 2544.900055] RSP: 0018:ffff8807653f7c80  EFLAGS: 00000202
> >> >>> [ 2544.900055] RAX: 0000000000000080 RBX: ffffffff813207fd RCX: 0000000000000080
> >> >>> [ 2544.900055] RDX: 0000000000000001 RSI: 0000000000000000 RDI: 0000000000000080
> >> >>> [ 2544.900055] RBP: ffff8807653f7cb0 R08: ffffffff8160d148 R09: ffff880770c006a8
> >> >>> [ 2544.900055] R10: 0000000000000020 R11: ffffea003b490700 R12: ffffffff810b859e
> >> >>> [ 2544.900055] R13: ffff8807653f7bf8 R14: ffffffff810b50e7 R15: ffff8807653f7be8
> >> >>> [ 2544.900055] FS:  00007f0c934cd780(0000) GS:ffff880ef0fe0000(0000) knlGS:0000000000000000
> >> >>> [ 2544.900055] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> >> >>> [ 2544.900055] CR2: 00007f0c934db000 CR3: 0000000764b0f000 CR4: 00000000001406e0
> >> >>> [ 2544.900055] Stack:
> >> >>> [ 2544.900055]  0000000106038000 000000000000000f 000000000000001f ffffffff81adcfe0
> >> >>> [ 2544.900055]  ffffffff810564e0 000000000000001f ffff8807653f7d20 ffffffff810cc195
> >> >>> [ 2544.900055]  00007f0c934db000 ffff8807653f7cd8 ffff880ef0ef74a8 ffff880ef0ef4d00
> >> >>> [ 2544.900055] Call Trace:
> >> >>> [ 2544.900055]  [<ffffffff810564e0>] ? leave_mm+0x70/0x70
> >> >>> [ 2544.900055]  [<ffffffff810cc195>] smp_call_function_single+0x135/0x170
> >> >>> [ 2544.900055]  [<ffffffff810564e0>] ? leave_mm+0x70/0x70
> >> >>> [ 2544.900055]  [<ffffffff810cc3c5>] smp_call_function_many+0x105/0x2b0
> >> >>> [ 2544.900055]  [<ffffffff810564e0>] ? leave_mm+0x70/0x70
> >> >>> [ 2544.900055]  [<ffffffff81056637>] native_flush_tlb_others+0x37/0x40
> >> >>> [ 2544.900055]  [<ffffffff810568ae>] flush_tlb_mm_range+0x1fe/0x250
> >> >>> [ 2544.900055]  [<ffffffff81167917>] tlb_flush_mmu+0x37/0xa0
> >> >>> [ 2544.900055]  [<ffffffff81167994>] tlb_finish_mmu+0x14/0x50
> >> >>> [ 2544.900055]  [<ffffffff8116fdc5>] unmap_region+0x105/0x120
> >> >>> [ 2544.900055]  [<ffffffff811cd01e>] ? mntput_no_expire+0x3e/0x140
> >> >>> [ 2544.900055]  [<ffffffff81170349>] ? vma_rb_erase+0x1c9/0x210
> >> >>> [ 2544.900055]  [<ffffffff81171f10>] do_munmap+0x280/0x370
> >> >>> [ 2544.900055]  [<ffffffff81172041>] vm_munmap+0x41/0x60
> >> >>> [ 2544.900055]  [<ffffffff81172f42>] SyS_munmap+0x22/0x30
> >> >>> [ 2544.900055]  [<ffffffff814d4e6d>] system_call_fastpath+0x1a/0x1f
> >> >>> [ 2544.900055] Code: 48 89 4b 08 48 89 19 e8 4f 05 40 00 4d 39 fc 8b 55 d4 75 0f 44 89 f7 ff 15 5e 8d 95 00 8b 55 d4 0f 1f 00 85 d2 75 06 eb 0a 66 90 <f3> 90 f6 43 20 01 75 f8 48 83 c4 08 5b 41 5c 41 5d 41 5e 41 5f
> >> >>>
> >> >>> At this point, the MD array will not accept any I/O, and any requests will just
> >> >>> result in additional soft lockup messages.
> >> >>>
> >> >>> I originally noticed this issue on Linux 3.13.3, and wasn't able to reproduce
> >> >>> it on 3.10.30. I eventually narrowed it down to a regression introduced between
> >> >>> 3.12 and 3.13. A bisection blames this commit:
> >> >>>
> >> >>> commit b795854b1fa70f6aee923ae5df74ff7afeaddcaa
> >> >>> Author: Mel Gorman <mgorman@...e.de>
> >> >>> Date:   Mon Oct 7 11:29:07 2013 +0100
> >> >>>
> >> >>>     sched/numa: Set preferred NUMA node based on number of private faults
> >> >>>
> >> >>>     Ideally it would be possible to distinguish between NUMA hinting faults that
> >> >>>     are private to a task and those that are shared. If treated identically
> >> >>>     there is a risk that shared pages bounce between nodes depending on
> >> >>>     the order they are referenced by tasks. Ultimately what is desirable is
> >> >>>     that task private pages remain local to the task while shared pages are
> >> >>>     interleaved between sharing tasks running on different nodes to give good
> >> >>>     average performance. This is further complicated by THP as even
> >> >>>     applications that partition their data may not be partitioning on a huge
> >> >>>     page boundary.
> >> >>>
> >> >>>     To start with, this patch assumes that multi-threaded or multi-process
> >> >>>     applications partition their data and that in general the private accesses
> >> >>>     are more important for cpu->memory locality in the general case. Also,
> >> >>>     no new infrastructure is required to treat private pages properly but
> >> >>>     interleaving for shared pages requires additional infrastructure.
> >> >>>
> >> >>>     To detect private accesses the pid of the last accessing task is required
> >> >>>     but the storage requirements are a high. This patch borrows heavily from
> >> >>>     Ingo Molnar's patch "numa, mm, sched: Implement last-CPU+PID hash tracking"
> >> >>>     to encode some bits from the last accessing task in the page flags as
> >> >>>     well as the node information. Collisions will occur but it is better than
> >> >>>     just depending on the node information. Node information is then used to
> >> >>>     determine if a page needs to migrate. The PID information is used to detect
> >> >>>     private/shared accesses. The preferred NUMA node is selected based on where
> >> >>>     the maximum number of approximately private faults were measured. Shared
> >> >>>     faults are not taken into consideration for a few reasons.
> >> >>>
> >> >>>     First, if there are many tasks sharing the page then they'll all move
> >> >>>     towards the same node. The node will be compute overloaded and then
> >> >>>     scheduled away later only to bounce back again. Alternatively the shared
> >> >>>     tasks would just bounce around nodes because the fault information is
> >> >>>     effectively noise. Either way accounting for shared faults the same as
> >> >>>     private faults can result in lower performance overall.
> >> >>>
> >> >>>     The second reason is based on a hypothetical workload that has a small
> >> >>>     number of very important, heavily accessed private pages but a large shared
> >> >>>     array. The shared array would dominate the number of faults and be selected
> >> >>>     as a preferred node even though it's the wrong decision.
> >> >>>
> >> >>>     The third reason is that multiple threads in a process will race each
> >> >>>     other to fault the shared page making the fault information unreliable.
> >> >>>
> >> >>>     Signed-off-by: Mel Gorman <mgorman@...e.de>
> >> >>>     [ Fix complication error when !NUMA_BALANCING. ]
> >> >>>     Reviewed-by: Rik van Riel <riel@...hat.com>
> >> >>>     Cc: Andrea Arcangeli <aarcange@...hat.com>
> >> >>>     Cc: Johannes Weiner <hannes@...xchg.org>
> >> >>>     Cc: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
> >> >>>     Signed-off-by: Peter Zijlstra <peterz@...radead.org>
> >> >>>     Link: http://lkml.kernel.org/r/1381141781-10992-30-git-send-email-mgorman@suse.de
> >> >>>     Signed-off-by: Ingo Molnar <mingo@...nel.org>
> >> >>>
> >> >>> Here's the bisection log:
> >> >>>
> >> >>>  # bad:  [d8ec26d7] Linux 3.13
> >> >>>  # good: [5e01dc7b] Linux 3.12
> >> >>>  # bad:  [42a2d923] Merge git://git.kernel.org/pub/scm/linux/kernel/gi
> >> >>>  # bad:  [4b4d2b46] Merge tag 'h8300-for-linus' of git://git.kernel.or
> >> >>>  # skip: [c224b76b] Merge tag 'nfs-for-3.13-1' of git://git.linux-nfs.
> >> >>>  # good: [ae1dd9bc] Staging: xillybus: quoted strings split across lin
> >> >>>  # good: [beb5bfe4] Merge tag 'fixes-nc-for-linus' of git://git.kernel
> >> >>>  # good: [f9efbce6] Merge tag 'dt-for-linus' of git://git.kernel.org/p
> >> >>>  # good: [ad5d6989] Merge branch 'perf-core-for-linus' of git://git.ke
> >> >>>  # bad:  [39cf275a] Merge branch 'sched-core-for-linus' of git://git.k
> >> >>>  # good: [e6628d5b] sched/numa: Reschedule task on preferred NUMA node
> >> >>>  # bad:  [04bb2f94] sched/numa: Adjust scan rate in task_numa_placemen
> >> >>>  # bad:  [e1dda8a7] sched/numa: Fix placement of workloads spread acro
> >> >>>  # bad:  [58d081b5] sched/numa: Avoid overloading CPUs on a preferred
> >> >>>  # good: [073b5bee] sched/numa: Remove check that skips small VMAs
> >> >>>  # bad:  [6fe6b2d6] sched/numa: Do not migrate memory immediately afte
> >> >>>  # bad:  [b795854b] sched/numa: Set preferred NUMA node based on numbe
> >> >>>
> >> >>> Anyone have any ideas why this change broke things? Is there any additional
> >> >>> information I can provide to help pin this down?
> >> >>>
> >> >>> - Steven
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