Re: triggering udev rules based on the state of udevd

[Kay Sievers <kay.sievers@vrfy.org>]

On Wed, 2008-07-02 at 12:26 -0400, Bill Nottingham wrote:
> Kay Sievers (kay.sievers@vrfy.org) said: 
> > > There doesn't seem to be a good happy medium that allows for degraded assembly
> > > when needed, but normal assembly in most cases. One potential way to do this
> > > would be to queue events such as these RAID-handling events as 'idle', or
> > > 'end of queue', such that they are always run at the end of queue after other
> > > events have run. Is that sort of thing possible?
> > 
> > What would be a "queue"? How would you define one?
> 
> The event queue... basically just a push an event to 'last'.
> 
> > Can't you run a "all I need is there" - check with every matching
> > device, and make sure, you serialize/lock things properly, and only
> > the last device/event would have all needed requirements and trigger
> > the action, all earlier would just need to give up. The s390 stuff
> > does things like that with the "collect" extra, Ubuntu has a
> > "watershed" extra, which may do something like you need.
> 
> watershed just locks to avoid running multiple instances of the same
> base command; it doesn't actually solve this. Moreover, just saying
> 'only the last device/event' isn't really proper - how do you tell what
> is 'last' in the event of a degraded raid array?

The same "last" that would say: "The event queue... basically just a
push an event to 'last'", I guess :)

What would be the "end" of the queue you want to push events to?

Kay