Re: nohz problem with idle time on old hardware

[Steven Rostedt]

On Wed, 13 Nov 2013 17:07:18 +0100 (CET)
Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:


> Right. It's telling you if NOHZ is enabled. It's not telling you that
> NOHZ is active.

Yeah, which makes this code rather silly:

in rcu_prepare_for_idle():

	/* Handle nohz enablement switches conservatively. */
	tne = ACCESS_ONCE(tick_nohz_enabled);
	if (tne != rdtp->tick_nohz_enabled_snap) {
		if (rcu_cpu_has_callbacks(cpu, NULL))
			invoke_rcu_core(); /* force nohz to see update. */
		rdtp->tick_nohz_enabled_snap = tne;
		return;
	}

-- Steve
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