Re: [PATCH 01/12] usbnet: introduce usbnet 3 command helpers

On Wed, Oct 10, 2012 at 1:51 PM, Oliver Neukum [off-list ref] wrote:

No, the problem is autoresume.

Suppose we have a device with two interface. Interface A be usbnet; interface B
something you page on. Now consider that you can only resume both interfaces
and this is (and needs to be) done synchronously.

Now we can have this code path:

autoresume of device -> resume() -> kmalloc(..., GFP_KERNEL) ->
VM layer decides to start paging out -> IO to interface B -> autoresume of device
--> DEADLOCK

Currently scsi disk can only be runtime suspended when the device is not
opened, so are you sure that the paging out above can cause IO on a suspend
usb mass storage disk which is not mounted or opened by utility now?


Thanks,
--
Ming Lei
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