Re: fanotify - overall design before I start sending patches

Peter Zijlstra
2009-08-06T10:29:44Z

On Thu, 2009-08-06 at 11:20 +0100, Douglas Leeder wrote:
> Pavel Machek wrote:
> > On Wed 2009-08-05 17:46:16, Tvrtko Ursulin wrote:
> >> On Wednesday 05 August 2009 03:05:34 Pavel Machek wrote:
>
> >> Just to make sure you haven't missed this - it is not that they have to
> >> complete the whole operation before the timeout period (since you mention
> >> realtime/mlock I suspect this is what you think?), but _during_ the operation
> >> they have to show that they are active by sending something like keep alive
> >> messages.
> >>
> >> Or you are worried about failing to meet even that on a loaded system? There
> >> has to be something like this otherwise hung userspace client would kill the
> >> whole system.
> >
> > Of course, I'm worried about failing to meet this on loaded
> > system. And the fact that I _have_ to worry about that means that
> > interface is ugly/broken.
>
> You mean that in 5 seconds, you won't have any point when you can tell
> the kernel, "I'm still working"?

I have to agree with Pavel here, either you demand the monitor process
is RT/mlock and can respond in time, in which case the interface doesn't
need a 5 second timeout, or you cannot and you have a hole somewhere.

Now having the kernel depend on any user task to guarantee process is of
course utterly insane too.

Sounds like a bad place to be, and I'd rather not have it.

If you really need the intermediate you might as well use a FUSE
filesystem, but I suspect there's plenty of problems there as well.

It all reeks of ugly though..

/me craws back from whence he came.