Re: [PATCH v1] ACPI / scan: Acquire device_hotplug_lock in acpi_scan_init()

[David Hildenbrand]

On 25.07.19 11:22, Rafael J. Wysocki wrote:
> On Thu, Jul 25, 2019 at 11:18 AM Oscar Salvador <osalvador@xxxxxxx> wrote:
>>
>> On Wed, Jul 24, 2019 at 04:30:17PM +0200, David Hildenbrand wrote:
>>> We end up calling __add_memory() without the device hotplug lock held.
>>> (I used a local patch to assert in __add_memory() that the
>>>  device_hotplug_lock is held - I might upstream that as well soon)
>>>
>>> [   26.771684]        create_memory_block_devices+0xa4/0x140
>>> [   26.772952]        add_memory_resource+0xde/0x200
>>> [   26.773987]        __add_memory+0x6e/0xa0
>>> [   26.775161]        acpi_memory_device_add+0x149/0x2b0
>>> [   26.776263]        acpi_bus_attach+0xf1/0x1f0
>>> [   26.777247]        acpi_bus_attach+0x66/0x1f0
>>> [   26.778268]        acpi_bus_attach+0x66/0x1f0
>>> [   26.779073]        acpi_bus_attach+0x66/0x1f0
>>> [   26.780143]        acpi_bus_scan+0x3e/0x90
>>> [   26.780844]        acpi_scan_init+0x109/0x257
>>> [   26.781638]        acpi_init+0x2ab/0x30d
>>> [   26.782248]        do_one_initcall+0x58/0x2cf
>>> [   26.783181]        kernel_init_freeable+0x1bd/0x247
>>> [   26.784345]        kernel_init+0x5/0xf1
>>> [   26.785314]        ret_from_fork+0x3a/0x50
>>>
>>> So perform the locking just like in acpi_device_hotplug().
>>>
>>> Cc: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx>
>>> Cc: Len Brown <lenb@xxxxxxxxxx
>>> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
>>> Cc: Oscar Salvador <osalvador@xxxxxxx>
>>> Cc: Michal Hocko <mhocko@xxxxxxxx>
>>> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
>>
>> Given that that call comes from a __init function, so while booting, I wonder
>> how bad it is.
> 
> Yes, it probably does not matter.

It can at least confuse lockdep, but I agree that this is not stable
material.

> 
>> Anyway, let us be consistent:
> 
> Right.
> 


-- 

Thanks,

David / dhildenb