Re: [ANNOUNCE] udev 0.1 release

Andrew Morton
2003-04-11T23:11:58Z

Greg KH <greg@kroah.com> wrote:
>
> On Fri, Apr 11, 2003 at 03:09:33PM -0700, Andrew Morton wrote:
> > Steven Dake <sdake@mvista.com> wrote:
> > >
> > > A much better solution could be had by select()ing on a filehandle
> > > indicating when a new hotswap event is ready to be processed. No races,
> > > no security issues, no performance issues.
> >
> > I must say that I've always felt this to be a better approach than the
> > /sbin/hotplug callout.
> >
> > Apart from the performance issue, it means that the kernel can buffer the
> > "insertion" events which happen at boot-time discovery until the userspace
> > handler attaches itself.
>
> But how many events to we buffer?

On a large machine: 856,432.

> When do we start to throw them away?
> Fun policy decisions that we don't have to worry about in the current
> scheme.

The current scheme will run out of processes, kernel stacks, etc before a
message scheme would.

> Also, what's the format of the kernel->user interface.

Exactly the same as at present, with /sbin/hotplug chopped off. So you can
run the daemon:

while read x
do
/sbin/hotplug $x
done < /dev/hotplug_event_pipe

for compatibility with existing scripts.

But I'm not really very opinionated about it. I don't expect any of it to be
super-robust, really.