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SubjectRe: intel-dmar: possible circular locking dependency detected
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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

--
Siemens AG, Corporate Technology, CT RDA ITP SES-DE
Corporate Competence Center Embedded Linux

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