[linux-pm] [PATCH 09/10] Input: Hold wake lock while event queue is not empty.

[Arve Hjønnevåg]

On Fri, Feb 13, 2009 at 4:09 PM, Matthew Garrett <mjg59 at srcf.ucam.org> wrote:
> On Fri, Feb 13, 2009 at 03:51:40PM -0800, Arve Hjønnevåg wrote:
>> On Thu, Feb 12, 2009 at 4:57 PM, Matthew Garrett <mjg59 at srcf.ucam.org> wrote:
>> > It's not the job of the kernel to guard against userspace doing foolish
>> > things.
>>
>> Not true. The kernel in general tries to protect processes from
>> causing harm to other processes or to the kernel itself.
>
> Harm, yes. This isn't harm. It's undesirable, in the same way that an
> application taking a wake lock and then spinning until your battery runs
> out is undesirable. It's not the kernel's job to prevent that.
>
>> > Either you want to wait for input events to be consumed before
>> > suspend or you don't - arbitrary timeouts provide no guarantees about
>> > the correctness of your platform's behaviour. The default permissions on
>> > the event devices mean that the only components that could interfere
>> > with this are ones under your control, so fixing them seems like the
>> > sensible approach.
>>
>> We did fix the bug. My point is that is it completely unreasonable for
>> the user space to code take more than 5 seconds to read an input
>> event. Trying to protecting the system (not the app) against this is
>> not unreasonable.
>
> Completely unreasoable *in your use case*. The kernel doesn't exist to
> satisfy only your use case - it has to satisfy as many as possible.
> That's why hardcoding policy decisions such as this timeout is a bad
> idea.

Which is why I offered to make it configurable.

-- 
Arve Hjønnevåg