Re: [PATCH 3/4] 2.6.2-rc2-mm2 CPU Hotplug: The Core

Ingo Molnar
2004-02-02T12:46:24Z

On Mon, 2 Feb 2004, Rusty Russell wrote:

> Unfortunately the __migrate_task() check won't go away: someone may have
> asked to move from CPU 0 to 1, and by the time migration thread on 0
> gets to the request, 1 has gone down. We don't want all the callers to
> hold the cpucontrol lock, because now the NUMA scheduler uses migration
> as a common case 8(

well, when a CPU goes down it could process the migration request queue as
well. (this would be a pretty natural thing to do if CPU-down executes in
the migration-thread context.)

Another question is user-space semantics - if user-space relies on CPU
affinity, is the kernel allowed to violate it or should the process be
notified. Sending it a signal (SIGTERM or anything similar) if the
affinity was non-generic might be a good thing to do.

Ingo