Re: wake_up vs. wake_up_sync

[Mike Kravetz]

On Wed, Jun 27, 2001 at 11:22:19PM +0200, Manfred Spraul wrote:
> > Why would you want to prevent
> > reschedule_idle()?
> > 
> If one process runs, wakes up another process and _knows_ that it's
> going to sleep immediately after the wake_up it doesn't need the
> reschedule_idle: the current cpu will be idle soon, the scheduler
> doesn't need to find another cpu for the woken up thread.

I'm curious.  How does the caller of wake_up_sync know that the
current cpu will soon be idle.  Does it assume that there are no
other tasks on the runqueue waiting for a CPU?  If there are other
tasks on the runqueue, isn't it possible that another task has a
higher goodness value than the task being awakened.  In such a case,
isn't is possible that the awakened task could sit on the runqueue
(waiting for a CPU) while tasks with a lower goodness value are
allowed to run?

-- 
Mike Kravetz                                 [e-mail]
IBM Linux Technology Center