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

On Tue, 20 Oct 2015 14:26:34 -0700
Andy Lutomirski [off-list ref] 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