On Tue, 11 Feb 2014, Daniel Lezcano wrote: > The idle main function is a complex and a critical function. Added more > comments to the code. > > Signed-off-by: Daniel Lezcano <[email protected]>
Few questions below. In any case,: Acked-by: Nicolas Pitre <[email protected]> > --- > kernel/sched/idle.c | 37 +++++++++++++++++++++++++++++++++---- > 1 file changed, 33 insertions(+), 4 deletions(-) > > diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c > index 72b5926..36ff1a7 100644 > --- a/kernel/sched/idle.c > +++ b/kernel/sched/idle.c > @@ -86,19 +86,34 @@ static int cpuidle_idle_call(void) > if (cpu_idle_force_poll || tick_check_broadcast_expired()) > return cpu_idle_poll(); > > + /* > + * Check if the idle task must rescheduled. If it is the case, s/must/must be/ > + * exit the function after re-enabling the local irq and set > + * again the polling flag > + */ > if (current_clr_polling_and_test()) { > local_irq_enable(); > __current_set_polling(); > return 0; > } > > + /* > + * During the idle period, stop measuring the disabled irqs > + * critical sections latencies > + */ > stop_critical_timings(); > + > + /* > + * Tell the RCU framework we are entering an idle section, > + * so no more rcu read side critical sections and one more > + * step to the grace period > + */ > rcu_idle_enter(); > > - /* Ask the governor for the next state, this call can fail for > - * different reasons: cpuidle is not enabled or an idle state > - * fulfilling the constraints was not found. In this case, we fall > - * back to the default idle function > + /* > + * Ask the governor to choose an idle state it thinks it is > + * convenient to go to. There is *always* a convenient idle > + * state but the call could fail if cpuidle is not enabled > */ > next_state = cpuidle_select(drv, dev); > if (next_state < 0) { > @@ -106,6 +121,10 @@ static int cpuidle_idle_call(void) > goto out; > } > > + /* > + * The idle task must be scheduled, it is pointless to go to idle, > + * just update no idle residency and get out of this function > + */ > if (need_resched()) { > dev->last_residency = 0; > /* give the governor an opportunity to reflect on the outcome */ Is this if block really necessary? We already have need_resched() being monitored in the outer loop. Are cpuidle_select() or rcu_idle_enter() likely to spend a significant amount of time justifying a recheck here? Nicolas -- 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/
