Re: [dm-devel][PATCH] Uevent cookie env var support

[Kay Sievers <kay sievers vrfy org>]

On Wed, Apr 8, 2009 at 06:20, Alasdair G Kergon <agk redhat com> wrote:
> On Wed, Apr 08, 2009 at 05:49:11AM -0700, Kay Sievers wrote:
>> I always thought we would return the driver core generated seqnum with
>> the ioctl,
>
> When Peter tried to make that work it needed more and more hacks
> piled onto it and instead he came up with this cookie method which seems
> to satisfy all our requirements with a minimum amount of change, fingers
> crossed.
>
> E.g. A problem with the other approach was: lvm2 userspace doesn't know the
> seqnum till after the uevent has fired and udev could complete processing
> before the lvm2 code has set itself up to wait for that seqnum so you have to
> build extra interlocking into the process making it much more complex.  If you
> wait for all events up to a given number you could get stuck behind some
> unrelated event on an unresponsive device, with is also unsatisfactory.

Yeah, sounds sensible, and like a nice solution to the problem if you
are able to watch the events udev sends out.

Thanks,
Kay