On Wed, Oct 10, 2012 at 1:51 PM, Oliver Neukum <oneu...@suse.de> 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
OK, thanks for your detailed explanation.
> We need to use GFP_NOIO in situations the helper cannot know about.
> Please add a gfp_t parameter. Then the caller will solve that.
Considered that most of drivers call the helpers in different context, I think
it is better to switch the gpf_t flag runtime inside helpers, like below:
if (dev->power.runtime_status == RPM_RESUMING)
gfp = GFP_NOIO;
else
gfp = GFP_KERNEL;
Thanks,
--
Ming Lei
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