Re: intel-dmar: possible circular locking dependency detected

[Jan Kiszka]

On 2017-09-27 14:14, Jan Kiszka wrote:
> Hi,
> 
> while I'm triggering this with a still out-of-tree module from the
> Jailhouse project, the potential deadlock appears to me being unrelated
> to it. Please have a look:
> 
> ======================================================
> WARNING: possible circular locking dependency detected
> 4.14.0-rc2-dbg+ #176 Tainted: G           O
> ------------------------------------------------------
> jailhouse/6105 is trying to acquire lock:
> dmar_pci_bus_notifier+0x4f/0xcb
> 
> but task is already holding lock:
> __blocking_notifier_call_chain+0x31/0x65
> 
> which lock already depends on the new lock.
> 
> 
> the existing dependency chain (in reverse order) is:
> 
> -> #1 (&(&priv->bus_notifier)->rwsem){++++}:
>        __lock_acquire+0xed7/0x113b
>        lock_acquire+0x148/0x1f6
>        down_write+0x3b/0x6a
>        blocking_notifier_chain_register+0x33/0x53
>        bus_register_notifier+0x1c/0x1e
>        dmar_dev_scope_init+0x2c6/0x2db
>        intel_iommu_init+0xec/0x11c2
>        pci_iommu_init+0x17/0x41
>        do_one_initcall+0x90/0x143
>        kernel_init_freeable+0x1cc/0x256
>        kernel_init+0xe/0xf8
>        ret_from_fork+0x2a/0x40
> 
> -> #0 (dmar_global_lock){++++}:
>        check_prev_add+0x112/0x65f
>        __lock_acquire+0xed7/0x113b
>        lock_acquire+0x148/0x1f6
>        down_write+0x3b/0x6a
>        dmar_pci_bus_notifier+0x4f/0xcb
>        notifier_call_chain+0x3c/0x5e
>        __blocking_notifier_call_chain+0x4c/0x65
>        blocking_notifier_call_chain+0x14/0x16
>        device_add+0x40c/0x522
>        pci_device_add+0x1c0/0x1ce
>        pci_scan_single_device+0x92/0x9d
>        pci_scan_slot+0x59/0x10a
>        jailhouse_pci_do_all_devices+0x74/0x263 [jailhouse]
>        jailhouse_pci_virtual_root_devices_add+0x40/0x42 [jailhouse]
>        jailhouse_cmd_enable+0x4fd/0x5e8 [jailhouse]
>        jailhouse_ioctl+0x28/0x70 [jailhouse]
>        vfs_ioctl+0x18/0x34
>        do_vfs_ioctl+0x51b/0x5e3
>        SyS_ioctl+0x50/0x7b
>        entry_SYSCALL_64_fastpath+0x1f/0xbe
> 
> other info that might help us debug this:
> 
>  Possible unsafe locking scenario:
> 
>        CPU0                    CPU1
>        ----                    ----
>   lock(&(&priv->bus_notifier)->rwsem);
>                                lock(dmar_global_lock);
>                                lock(&(&priv->bus_notifier)->rwsem);
>   lock(dmar_global_lock);
> 
>  *** DEADLOCK ***
> 
> 2 locks held by jailhouse/6105:
> jailhouse_cmd_enable+0x130/0x5e8 [jailhouse]
> __blocking_notifier_call_chain+0x31/0x65
> 
> stack backtrace:
> CPU: 1 PID: 6105 Comm: jailhouse Tainted: G           O
> 4.14.0-rc2-dbg+ #176
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS
> rel-1.10.2-0-g5f4c7b1-prebuilt.qemu-project.org 04/01/2014
> Call Trace:
>  dump_stack+0x85/0xbe
>  print_circular_bug+0x389/0x398
>  ? add_lock_to_list.isra.23+0x96/0x96
>  check_prev_add+0x112/0x65f
>  ? kernel_text_address+0x1c/0x6a
>  ? add_lock_to_list.isra.23+0x96/0x96
>  __lock_acquire+0xed7/0x113b
>  ? __lock_acquire+0xed7/0x113b
>  lock_acquire+0x148/0x1f6
>  ? dmar_pci_bus_notifier+0x4f/0xcb
>  down_write+0x3b/0x6a
>  ? dmar_pci_bus_notifier+0x4f/0xcb
>  dmar_pci_bus_notifier+0x4f/0xcb
>  notifier_call_chain+0x3c/0x5e
>  __blocking_notifier_call_chain+0x4c/0x65
>  blocking_notifier_call_chain+0x14/0x16
>  device_add+0x40c/0x522
>  pci_device_add+0x1c0/0x1ce
>  pci_scan_single_device+0x92/0x9d
>  pci_scan_slot+0x59/0x10a
>  jailhouse_pci_do_all_devices+0x74/0x263 [jailhouse]
>  jailhouse_pci_virtual_root_devices_add+0x40/0x42 [jailhouse]
>  jailhouse_cmd_enable+0x4fd/0x5e8 [jailhouse]
>  jailhouse_ioctl+0x28/0x70 [jailhouse]
>  vfs_ioctl+0x18/0x34
>  do_vfs_ioctl+0x51b/0x5e3
>  ? kmem_cache_free+0x15b/0x1fa
>  ? entry_SYSCALL_64_fastpath+0x5/0xbe
>  ? trace_hardirqs_on_caller+0x180/0x19c
>  SyS_ioctl+0x50/0x7b
>  entry_SYSCALL_64_fastpath+0x1f/0xbe
> RIP: 0033:0x7f8b3b110d87
> RSP: 002b:00007ffc44b70088 EFLAGS: 00000206 ORIG_RAX: 0000000000000010
> RAX: ffffffffffffffda RBX: 0000000000000046 RCX: 00007f8b3b110d87
> RDX: 0000000000604010 RSI: 0000000040080000 RDI: 0000000000000003
> RBP: 0000000000604010 R08: 00007f8b3b3ade80 R09: 00000000000885d0
> R10: 00007ffc44b6fe40 R11: 0000000000000206 R12: 00000000000025d4
> R13: 0000000000000000 R14: 00007ffc44b714a4 R15: 0000000000000000
> 
> Thanks,
> Jan
> 

Oh, just realized that I already sent this report earlier this year [1]
but didn't receive any feedback so far.

Jan

[1] https://lkml.org/lkml/2017/7/24/238

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