Messages in this thread |  | | Date | Wed, 13 Nov 2013 08:18:29 -0800 | From | "Paul E. McKenney" <> | Subject | Re: nohz problem with idle time on old hardware |
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On Wed, Nov 13, 2013 at 11:12:57AM -0500, Steven Rostedt wrote: > On Wed, 13 Nov 2013 17:07:18 +0100 (CET) > Thomas Gleixner <tglx@linutronix.de> 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; > }
OK, what should I be checking instead? Not much point in trying to get RCU out of the way of disabling the scheduling-clock interrupt if NOHZ is disabled. ;-)
Thanx, Paul
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