Re: [PATCH v5 tip/core/rcu 15/16] rcu: Make RCU-tasks wait for idle tasks

From: Peter Zijlstra
Date: Wed Aug 13 2014 - 10:07:35 EST

On Wed, Aug 13, 2014 at 09:51:32AM -0400, Steven Rostedt wrote:

> I still need to look at the patches, but if this is just for the idle
> case, then we don't need it. The idle case can be solved with a simple
> sched_on_each_cpu(). I need a way to solve waiting for processes to
> finish from a preemption point.
> That's all I want, and if we can remove the "idle" case and document it
> well that it's not covered and a sched_on_each_cpu() may be needed,
> then I'm fine with that.
> sched_on_each_cpu(dummy_op);
> call_rcu_tasks(free_tramp);

Sure, but why not dtrt and push rcu_idle hooks all the way down into the
idle drivers if and where appropriate?

There isn't _that_ much idle driver code. Also, some stuff should be
cleaned up; we're already calling stop_critical_timings() in the generic
idle code, and then calling it again in the cpuidle drivers.

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