2012/12/3 Vincent Guittot <vincent.guit...@linaro.org>: > With the coupled cpuidle driver (but probably also with other drivers), > a CPU loops in a temporary safe state while waiting for other CPUs of its > cluster to be ready to enter the coupled C-state. If an IRQ or a softirq > occurs, the CPU will stay in this internal loop if there is no need > to resched. The SCHED softirq clears the NOHZ and increases > nr_busy_cpus. If there is no need to resched, we will not call > set_cpu_sd_state_idle because of this internal loop in a cpuidle state. > We have to call set_cpu_sd_state_idle in tick_nohz_irq_exit which is used > to handle such situation.
I'm a bit confused with this. set_cpu_sd_state_busy() is only called from nohz_kick_needed(). And it checks idle_cpu() before doing anything. So if no task is going to be scheduled, idle_cpu() prevents from calling set_cpu_sd_state_busy(). I'm probably missing something. Thanks. > > Signed-off-by: Vincent Guittot <vincent.guit...@linaro.org> > --- > kernel/time/tick-sched.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c > index 955d35b..b8d74ea 100644 > --- a/kernel/time/tick-sched.c > +++ b/kernel/time/tick-sched.c > @@ -570,6 +570,8 @@ void tick_nohz_irq_exit(void) > if (!ts->inidle) > return; > > + set_cpu_sd_state_idle(); > + > /* Cancel the timer because CPU already waken up from the C-states*/ > menu_hrtimer_cancel(); > __tick_nohz_idle_enter(ts); > -- > 1.7.9.5 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ _______________________________________________ linaro-dev mailing list linaro-dev@lists.linaro.org http://lists.linaro.org/mailman/listinfo/linaro-dev
