Inconsistent lock state with Hyper-V memory balloon?

[Sitsofe Wheeler]

I've been trying to use the Hyper-V balloon driver to allow the host to
reclaim unused memory but have been hitting issues. With a Hyper-V 2012
R2 guest with 4GBytes of RAM, dynamic memory on, 1GByte minimum 10GByte
maximum, 8 vcpus, running a 3.18.0-rc3 kernel with no swap configured
the following lockdep splat occurred:

=================================
[ INFO: inconsistent lock state ]
3.18.0-rc3.x86_64 #159 Not tainted
---------------------------------
inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.
swapper/0/0 [HC0[0]:SC1[1]:HE1:SE0] takes:
 (bdev_lock){+.?...}, at: [<ffffffff811ff39c>] nr_blockdev_pages+0x1c/0x80
{SOFTIRQ-ON-W} state was registered at:
  [<ffffffff810ba03d>] __lock_acquire+0x87d/0x1c60
  [<ffffffff810bbcdc>] lock_acquire+0xfc/0x150
  [<ffffffff816e4019>] _raw_spin_lock+0x39/0x50
  [<ffffffff811ff39c>] nr_blockdev_pages+0x1c/0x80
  [<ffffffff8115d5f7>] si_meminfo+0x47/0x70
  [<ffffffff81d6622f>] eventpoll_init+0x11/0x10a
  [<ffffffff81d3d150>] do_one_initcall+0xf9/0x1a7
  [<ffffffff81d3d3d2>] kernel_init_freeable+0x1d4/0x268
  [<ffffffff816ce0ae>] kernel_init+0xe/0x100
  [<ffffffff816e4dfc>] ret_from_fork+0x7c/0xb0
irq event stamp: 2660283708
hardirqs last  enabled at (2660283708): [<ffffffff8115eef5>] free_hot_cold_page+0x175/0x190
hardirqs last disabled at (2660283707): [<ffffffff8115ee25>] free_hot_cold_page+0xa5/0x190
softirqs last  enabled at (2660132034): [<ffffffff81071e6a>] _local_bh_enable+0x4a/0x50
softirqs last disabled at (2660132035): [<ffffffff81072478>] irq_exit+0x58/0xc0

might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(bdev_lock);
  <Interrupt>
    lock(bdev_lock);

*

no locks held by swapper/0/0.


CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.18.0-rc3.x86_64 #159
Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS 090006  05/23/2012
 ffffffff8266ac90 ffff880107403af8 ffffffff816db3ef 0000000000000000
 ffffffff81c134c0 ffff880107403b58 ffffffff816d6fd3 0000000000000001
 ffffffff00000001 ffff880100000000 ffffffff81010e6f 0000000000000046
Call Trace:
 <IRQ>  [<ffffffff816db3ef>] dump_stack+0x4e/0x68
 [<ffffffff816d6fd3>] print_usage_bug+0x1f3/0x204
 [<ffffffff81010e6f>] ? save_stack_trace+0x2f/0x50
 [<ffffffff810b6f40>] ? print_irq_inversion_bug+0x200/0x200
 [<ffffffff810b78e6>] mark_lock+0x176/0x2e0
 [<ffffffff810b9f83>] __lock_acquire+0x7c3/0x1c60
 [<ffffffff8103d548>] ? lookup_address+0x28/0x30
 [<ffffffff8103d58b>] ? _lookup_address_cpa.isra.3+0x3b/0x40
 [<ffffffff813c4e89>] ? __debug_check_no_obj_freed+0x89/0x220
 [<ffffffff810bbcdc>] lock_acquire+0xfc/0x150
 [<ffffffff811ff39c>] ? nr_blockdev_pages+0x1c/0x80
 [<ffffffff816e4019>] _raw_spin_lock+0x39/0x50
 [<ffffffff811ff39c>] ? nr_blockdev_pages+0x1c/0x80
 [<ffffffff811ff39c>] nr_blockdev_pages+0x1c/0x80
 [<ffffffff8115d5f7>] si_meminfo+0x47/0x70
 [<ffffffff815eb14d>] post_status.isra.3+0x6d/0x190
 [<ffffffff810b7f4d>] ? trace_hardirqs_on+0xd/0x10
 [<ffffffff8115f00f>] ? __free_pages+0x2f/0x60
 [<ffffffff815eb34f>] ? free_balloon_pages.isra.5+0x8f/0xb0
 [<ffffffff815eb972>] balloon_onchannelcallback+0x212/0x380
 [<ffffffff815e69d3>] vmbus_on_event+0x173/0x1d0
 [<ffffffff81071b47>] tasklet_action+0x127/0x160
 [<ffffffff81071ffa>] __do_softirq+0x18a/0x340
 [<ffffffff81072478>] irq_exit+0x58/0xc0
 [<ffffffff810290c5>] hyperv_vector_handler+0x45/0x60
 [<ffffffff816e6b92>] hyperv_callback_vector+0x72/0x80
 <EOI>  [<ffffffff81037b76>] ? native_safe_halt+0x6/0x10
 [<ffffffff810b7f4d>] ? trace_hardirqs_on+0xd/0x10
 [<ffffffff8100c8d1>] default_idle+0x51/0xf0
 [<ffffffff8100d30f>] arch_cpu_idle+0xf/0x20
 [<ffffffff810b01e7>] cpu_startup_entry+0x217/0x3f0
 [<ffffffff816ce099>] rest_init+0xc9/0xd0
 [<ffffffff816cdfd5>] ? rest_init+0x5/0xd0
 [<ffffffff81d3d04a>] start_kernel+0x438/0x445
 [<ffffffff81d3c94a>] ? set_init_arg+0x57/0x57
 [<ffffffff81d3c120>] ? early_idt_handlers+0x120/0x120
 [<ffffffff81d3c59f>] x86_64_start_reservations+0x2a/0x2c
 [<ffffffff81d3c6df>] x86_64_start_kernel+0x13e/0x14d

Any help deciphering the above is greatly appreciated!

-- 
Sitsofe | http://sucs.org/~sits/
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/