Re: realtime scheduling problems with 2.4 linux kernel >= 2.4.10

[Andrew Morton]

Robert Love wrote:
> 
> On Mon, 2002-06-03 at 13:08, Andrew Morton wrote:
> 
> > keventd is a "process context bottom half handler".  It's designed
> > for use by interrupt handlers for handing off awkward, occasional
> > things which need process context.  For example, device hotplugging,
> > which was the original reason for its introduction.
> >
> > So it makes sense to give keventd SCHED_RR policy and maximum
> > priority.  Which should fix this problem as well, yes?
> 
> Next to ditching keventd, this is probably the best thing we can do.

I think the design is OK.  It's for "misc stuff".  There's only
a single instance, it's only lightly used.

> I wonder how much code _really_ needs it - that is, what really needs to
> be running in process-context?

Pretty much every use of keventd make sense as-is, IMO.

>  Obviously device hotplug probably does.
> But for things like that, what about spawning (temporarily) a kernel
> thread?

We need process context for starting a thread...

It's just an 8k stack.  I believe that keventd is OK, as
long as people don't go nuts when using it.   It may make
some sense to overload ksoftirqd to provide keventd functionality.
Except ksoftirqd runs at super-low priority, which is exactly
what keventd doesn't want.

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