Luis Henriques wrote:
> Hi,
>
> Since I am not sure if this problem has already been reported, here it goes.
>
> My log gets the following messages in -tip tree.  I don't know for how long this
> issue is around and whether the problem is on lockdep or on kvm.  After the
> first lockdep message, I get a huge amount of BUGs from kvm (which stop only
> when I kill kvm).  So, I believe issue is on kvm.
>
> I am running on an AMD64.  Please let me know if more info is needed (config,
> etc).
>
> [ 3293.134688] BUG: MAX_LOCK_DEPTH too low!
>   

Looks like a genuine issue, need to increase MAX_LOCK_DEPTH.  Andrea?

> [ 3293.134704] turning off the locking correctness validator.
> [ 3293.134718] Pid: 5117, comm: kvm Not tainted 2.6.30-rc1-tip-01420-g58e70a8
> #18
> [ 3293.134727] Call Trace:
> [ 3293.134749]  [<ffffffff802805f6>] __lock_acquire+0x4c6/0xbf0
> [ 3293.134764]  [<ffffffff80280e2e>] lock_acquire+0x10e/0x160
> [ 3293.134780]  [<ffffffff802f3760>] ? mm_take_all_locks+0x110/0x150
> [ 3293.134798]  [<ffffffff80580c3b>] _spin_lock_nest_lock+0x3b/0x50
> [ 3293.134811]  [<ffffffff802f3760>] ? mm_take_all_locks+0x110/0x150
> [ 3293.134823]  [<ffffffff802f3760>] mm_take_all_locks+0x110/0x150
> [ 3293.134838]  [<ffffffff803093af>] do_mmu_notifier_register+0xdf/0x1f0
> [ 3293.134852]  [<ffffffff803094f3>] mmu_notifier_register+0x13/0x20
> [ 3293.134899]  [<ffffffffa02edede>] kvm_dev_ioctl+0x1ae/0x360 [kvm]
> [ 3293.134914]  [<ffffffff80327a16>] vfs_ioctl+0x36/0xb0
> [ 3293.134927]  [<ffffffff80327b22>] do_vfs_ioctl+0x92/0x5c0
> [ 3293.134942]  [<ffffffff80273d9b>] ? up_read+0x2b/0x40
> [ 3293.134955]  [<ffffffff8032809f>] sys_ioctl+0x4f/0x80
> [ 3293.134971]  [<ffffffff8020c1f2>] system_call_fastpath+0x16/0x1b request
>   


> [ 3297.598606] BUG: using smp_processor_id() in preemptible [00000000] code: kvm/5118
> [ 3297.598630] caller is kvm_arch_vcpu_ioctl_run+0x61c/0xd10 [kvm]
> [ 3297.598635] Pid: 5118, comm: kvm Not tainted 2.6.30-rc1-tip-01420-g58e70a8 #18
> [ 3297.598638] Call Trace:
> [ 3297.598647]  [<ffffffff803d9db3>] debug_smp_processor_id+0xe3/0xf0
> [ 3297.598660]  [<ffffffffa02f684c>] kvm_arch_vcpu_ioctl_run+0x61c/0xd10 [kvm]
> [ 3297.598667]  [<ffffffff8032de67>] ? file_update_time+0xc7/0x130
> [ 3297.598672]  [<ffffffff802ed26b>] ? do_wp_page+0x1eb/0x7e0
> [ 3297.598684]  [<ffffffffa02ebb23>] kvm_vcpu_ioctl+0x4b3/0x8f0 [kvm]
> [ 3297.598691]  [<ffffffff805804d6>] ? trace_hardirqs_on_thunk+0x3a/0x3f
> [ 3297.598696]  [<ffffffff80581a35>] ? do_IRQ+0x95/0x100
> [ 3297.598702]  [<ffffffff8025c85a>] ? irq_exit+0x8a/0xc0
> [ 3297.598707]  [<ffffffff80327a16>] vfs_ioctl+0x36/0xb0
> [ 3297.598712]  [<ffffffff80327b22>] do_vfs_ioctl+0x92/0x5c0
> [ 3297.598716]  [<ffffffff8032809f>] sys_ioctl+0x4f/0x80
> [ 3297.598723]  [<ffffffff8020c1f2>] system_call_fastpath+0x16/0x1b
>   

This might be fixed by the attached patch.


-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.