> -----Original Message----- > From: Peter Zijlstra [mailto:peterz@xxxxxxxxxxxxx] > Sent: Monday, November 10, 2014 1:44 AM > To: Sitsofe Wheeler > Cc: KY Srinivasan; Haiyang Zhang; devel@xxxxxxxxxxxxxxxxxxxxxx; Ingo Molnar; > linux-kernel@xxxxxxxxxxxxxxx > Subject: Re: Inconsistent lock state with Hyper-V memory balloon? > > On Sat, Nov 08, 2014 at 02:36:54PM +0000, Sitsofe Wheeler wrote: > > 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! > > Its fairly simple, the first trace shows where bdev_lock was taken with > softirqs enabled, and the second trace shows where its taken from softirqs. > Combine the two and you've got a recursive deadlock. > > I don't know the block layer very well, but a quick glance at the code shows > its bdev_lock isn't meant to be used from softirq context, therefore the > hyperv stuff is broken. > > So complain to the hyperv people. Sitsofe, I am on vacation in India till the the 17th of November. I will look at this and fix this issue when I get back. Regards, K. Y _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
