======================================================
WARNING: possible circular locking dependency detected
4.13.0-rc6-next-20170824+ #8 Not tainted
------------------------------------------------------
kworker/0:1/24 is trying to acquire lock:
 ((&irqfd->shutdown)){+.+.}, at: [<ffffffff8146458c>] process_one_work+0xb2c/0x1be0 kernel/workqueue.c:2094

but now in release context of a crosslock acquired at the following:
 ((complete)&rcu.completion){+.+.}, at: [<ffffffff815afff5>] __synchronize_srcu+0x1b5/0x250 kernel/rcu/srcutree.c:898

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 ((complete)&rcu.completion){+.+.}:
       check_prevs_add kernel/locking/lockdep.c:2020 [inline]
       validate_chain kernel/locking/lockdep.c:2469 [inline]
       __lock_acquire+0x3286/0x4620 kernel/locking/lockdep.c:3498
       lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:4002
       complete_acquire include/linux/completion.h:39 [inline]
       __wait_for_common kernel/sched/completion.c:108 [inline]
       wait_for_common kernel/sched/completion.c:122 [inline]
       wait_for_completion+0xc8/0x770 kernel/sched/completion.c:143
       __synchronize_srcu+0x1b5/0x250 kernel/rcu/srcutree.c:898
       synchronize_srcu_expedited kernel/rcu/srcutree.c:923 [inline]
       synchronize_srcu+0x1a3/0x560 kernel/rcu/srcutree.c:974
       kvm_irqfd_assign arch/x86/kvm/../../../virt/kvm/eventfd.c:364 [inline]
       kvm_irqfd+0x994/0x1d50 arch/x86/kvm/../../../virt/kvm/eventfd.c:572
       kvm_vm_ioctl+0x1079/0x1c40 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3032
       vfs_ioctl fs/ioctl.c:45 [inline]
       do_vfs_ioctl+0x1b1/0x1530 fs/ioctl.c:685
       SYSC_ioctl fs/ioctl.c:700 [inline]
       SyS_ioctl+0x8f/0xc0 fs/ioctl.c:691
       entry_SYSCALL_64_fastpath+0x1f/0xbe

-> #1 (&kvm->irqfds.resampler_lock){+.+.}:
       check_prevs_add kernel/locking/lockdep.c:2020 [inline]
       validate_chain kernel/locking/lockdep.c:2469 [inline]
       __lock_acquire+0x3286/0x4620 kernel/locking/lockdep.c:3498
       lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:4002
       __mutex_lock_common kernel/locking/mutex.c:756 [inline]
       __mutex_lock+0x16f/0x1870 kernel/locking/mutex.c:893
       mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
       irqfd_resampler_shutdown+0xe3/0x6b0 arch/x86/kvm/../../../virt/kvm/eventfd.c:98
       irqfd_shutdown+0xd8/0x1a0 arch/x86/kvm/../../../virt/kvm/eventfd.c:137
       process_one_work+0xbfd/0x1be0 kernel/workqueue.c:2098
       worker_thread+0x223/0x1860 kernel/workqueue.c:2233
       kthread+0x39c/0x470 kernel/kthread.c:231
       ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431

-> #0 ((&irqfd->shutdown)){+.+.}:
       process_one_work+0xba5/0x1be0 kernel/workqueue.c:2095
       worker_thread+0x223/0x1860 kernel/workqueue.c:2233
       kthread+0x39c/0x470 kernel/kthread.c:231
       ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431
       0xffffffffffffffff

other info that might help us debug this:

Chain exists of:
  (&irqfd->shutdown) --> &kvm->irqfds.resampler_lock --> (complete)&rcu.completion

 Possible unsafe locking scenario by crosslock:

       CPU0                    CPU1
       ----                    ----
  lock(&kvm->irqfds.resampler_lock);
  lock((complete)&rcu.completion);
                               lock((&irqfd->shutdown));
                               unlock((complete)&rcu.completion);

 *** DEADLOCK ***

3 locks held by kworker/0:1/24:
 #0:  ("events_power_efficient"){.+.+}, at: [<ffffffff81464534>] __write_once_size include/linux/compiler.h:305 [inline]
 #0:  ("events_power_efficient"){.+.+}, at: [<ffffffff81464534>] atomic64_set arch/x86/include/asm/atomic64_64.h:33 [inline]
 #0:  ("events_power_efficient"){.+.+}, at: [<ffffffff81464534>] atomic_long_set include/asm-generic/atomic-long.h:56 [inline]
 #0:  ("events_power_efficient"){.+.+}, at: [<ffffffff81464534>] set_work_data kernel/workqueue.c:617 [inline]
 #0:  ("events_power_efficient"){.+.+}, at: [<ffffffff81464534>] set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 #0:  ("events_power_efficient"){.+.+}, at: [<ffffffff81464534>] process_one_work+0xad4/0x1be0 kernel/workqueue.c:2090
 #1:  ((&(&sdp->work)->work)){+.+.}, at: [<ffffffff8146458c>] process_one_work+0xb2c/0x1be0 kernel/workqueue.c:2094
 #2:  (&x->wait#5){....}, at: [<ffffffff81524c68>] complete+0x18/0x80 kernel/sched/completion.c:34

stack backtrace:
CPU: 0 PID: 24 Comm: kworker/0:1 Not tainted 4.13.0-rc6-next-20170824+ #8
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events_power_efficient srcu_invoke_callbacks
Call Trace:
 __dump_stack lib/dump_stack.c:16 [inline]
 dump_stack+0x194/0x257 lib/dump_stack.c:52
 print_circular_bug+0x503/0x710 kernel/locking/lockdep.c:1259
 check_prev_add+0x865/0x1520 kernel/locking/lockdep.c:1894
 commit_xhlock kernel/locking/lockdep.c:5002 [inline]
 commit_xhlocks kernel/locking/lockdep.c:5046 [inline]
 lock_commit_crosslock+0xe73/0x1d10 kernel/locking/lockdep.c:5085
 complete_release_commit include/linux/completion.h:49 [inline]
 complete+0x24/0x80 kernel/sched/completion.c:39
 wakeme_after_rcu+0xd/0x10 kernel/rcu/update.c:376
 srcu_invoke_callbacks+0x280/0x4d0 kernel/rcu/srcutree.c:1161
 process_one_work+0xbfd/0x1be0 kernel/workqueue.c:2098
 worker_thread+0x223/0x1860 kernel/workqueue.c:2233
 kthread+0x39c/0x470 kernel/kthread.c:231
 ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431