Re: linux-next 20111025: warnings in rcu_idle_exit_common()/rcu_idle_enter_common()

Steven Rostedt
2011-11-02T14:56:30Z

On Wed, 2011-11-02 at 07:44 -0700, Paul E. McKenney wrote:

> rcu: Fix idle-task checks
>
> RCU has traditionally relied on idle_cpu() to determine whether a given
> CPU is running in the context of an idle task, but recent changes have
> invalidated this approach.

Correct. idle_cpu() returns if the CPU is idle or not, not if the CPU is
running the idle thread. If the CPU wakes up on the idle thread and
there's tasks on the run queue, then idle_cpu() will return false, even
though the task running is the idle thread. But the CPU itself is not
technically idle.

Acked-by: Steven Rostedt <rostedt@goodmis.org>

-- Steve