Re: [PATCH v8 04/14] task_isolation: add initial support

Steven Rostedt
2015-10-21T00:29:29Z

On Tue, 20 Oct 2015 14:26:34 -0700
Andy Lutomirski <luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org> wrote:

> I'm not a scheduler person, so I don't know. But "don't run me unless
> I'm isolated" seems like a design that will, at best, only ever work
> by dumb luck. You have to disable migration, avoid other runnable
> tasks, hope that the kernel keeps working the way it did when you
> wrote the patch, hope you continue to get lucky enough that you ever
> get to user mode in the first place, etc.

Since it only makes sense to run one isolated task per cpu (not more
than one on the same CPU), I wonder if we should add a new interface
for this, that would force everything else off the CPU that it
requests. That is, you bind a task to a CPU, and then change it to
SCHED_ISOLATED (or what not), and the kernel will force all other tasks
off that CPU. Well, we would still have kernel threads, but that's a
different matter.

Also, doesn't RCU need to have a few ticks go by before it can safely
disable itself from userspace? I recall something like that. Paul?

-- Steve