Re: [PATCH] [RFC] Add support for uevents on block device idle changes

Kay Sievers
2009-11-19T14:35:06Z

On Thu, Nov 19, 2009 at 15:30, Matthew Garrett <mjg59@srcf.ucam.org> wrote:
> On Thu, Nov 19, 2009 at 03:25:59PM +0100, Kay Sievers wrote:
>> On Thu, Nov 19, 2009 at 15:16, Matthew Garrett <mjg59@srcf.ucam.org> wrote:
>> > It could, but it seems a bit of a hack. It'd still also require the
>> > timer to be in the kernel, so we might as well expose that to userspace.
>>
>> Sure, but a userspace configurable policy for an in-kernel disk-idle
>> powermanagent sounds fine, compared to a single-subscriber
>> userspace-only disk-idle event interface. :)
>
> Well, we still need to expose this for the access pattern modifying. I
> really don't see the issue with the single subscriber being devkit-disks
> - none of the operations involved are atomic, so we're inherently racy
> here.

Single-subscriber event interfaces are usually a no-go for generic
infrastructure like this. We still have the unmodified HAL running
until it is dead, and this works only because there are no such
awkward interfaces. In a few years we will probably have diskfoo
replacing dk-disks, and then ... :)

Kay