Re: [RFC] reliability and scalability

[Olaf Hering <olh@suse.de>]

 On Sat, Feb 07, Greg KH wrote:

> On Sat, Feb 07, 2004 at 09:57:58AM +0100, Olaf Hering wrote:
> >  On Sat, Feb 07, Chris Friesen wrote:
> > 
> > > Comments, anyone?
> > 
> > Better get rid of udevd and keep track of the latest add and remove
> > SEQNUMs in the database.  unlink the devnodes and symlinks before
> > creating new ones during add events.
> 
> And how would you re-order events in this situation?

What do you mean with reorder? Maybe I miss the point.


I assume the database has some locking to serialize writes (maybe even
reads).
- If an add event arrives, check if a remove event was recoreded.
  If the remove event had a higher number than this add event, record this
  add event as seen if no newer add event was seen, then exit.
  If no remove and no newer add event was seen, unlink the node and
  symlinks and recreate them. Record the current number as 'add'.
- If a remove event arrives, check if an add event was recorded.
  If the add event had a higher number, record this remove event if no
  newer remove event was seen, then exit.

Maybe something like this:

switch(action)
        case add:
                if (last.add > seqnum)
                        exit
                if (last.remove > seqnum)
                        exit
                last.add = seqnum
                unlink (node)
                mknod (node)
                if (symlink) {
                        unlink (symlink)
                        ln (node, symlink)
                }
                exit

        case remove:
                if (last.add > seqnum)
                        exit
                if (last.remove > seqnum)
                        exit
                last.remove = seqnum
                unlink (node)
                if (symlink)
                        unlink (symlink)
                exit

> No, udevd is needed.

I'm not convinced.

-- 
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sUse lINUX ag, n√úRNBERG


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