On Sat, Jul 19, 2014 at 02:44:15AM +0200, Frederic Weisbecker wrote: > When a CPU wakes up from idle and finds out that the timekeeper is > sleeping, we need to kick it such that it switches from dynticks to > periodic mode to maintain its timekeeping duty on behalf of the newly > awoken CPU. > > However we aren't using the right API for that. rcu_kick_nohz_cpu() is > aimed at waking full dynticks CPUs and not the timekeeper. > > Moreover the timekeeper must perform a new dynticks cycle to check the > new sysidle state and restart the tick if necessary. A simple call > to irq_exit() isn't enough. > > wake_up_nohz_cpu() is a good fit for that job because it pulls the > target out of the idle loop and restart the tick. Then if no other > task waits for the CPU, it will reenter the idle loop and then the > new sysidle state will be visible and well handled. > > Cc: Ingo Molnar <[email protected]> > Cc: Paul E. McKenney <[email protected]> > Cc: Peter Zijlstra <[email protected]> > Cc: Steven Rostedt <[email protected]> > Cc: Thomas Gleixner <[email protected]> > Cc: Viresh Kumar <[email protected]> > Signed-off-by: Frederic Weisbecker <[email protected]>
Either name is fine by me... ;-) Reviewed-by: Paul E. McKenney <[email protected]> > --- > kernel/rcu/tree_plugin.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h > index 395c14d..b65da1a 100644 > --- a/kernel/rcu/tree_plugin.h > +++ b/kernel/rcu/tree_plugin.h > @@ -2494,7 +2494,7 @@ void rcu_sysidle_force_exit(void) > oldstate, RCU_SYSIDLE_NOT); > if (oldstate == newoldstate && > oldstate == RCU_SYSIDLE_FULL_NOTED) { > - rcu_kick_nohz_cpu(tick_do_timer_cpu); > + wake_up_nohz_cpu(tick_do_timer_cpu); > return; /* We cleared it, done! */ > } > oldstate = newoldstate; > -- > 1.8.3.1 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to [email protected] > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
