Messages in this thread Patch in this message | | | From | Daniel Lezcano <> | Subject | [PATCH V3 5/5] idle: Add more comments to the code | Date | Tue, 25 Feb 2014 09:08:53 +0100 |
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The idle main function is a complex and a critical function. Added more comments to the code.
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org> Acked-by: Nicolas Pitre <nico@linaro.org> --- Changelog:
V2: * fixed typo in comment --- kernel/sched/idle.c | 43 +++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 41 insertions(+), 2 deletions(-)
Index: cpuidle-next/kernel/sched/idle.c =================================================================== --- cpuidle-next.orig/kernel/sched/idle.c +++ cpuidle-next/kernel/sched/idle.c @@ -76,20 +76,48 @@ static int cpuidle_idle_call(void) int next_state, entered_state; bool broadcast; + /* + * Check if the idle task must be rescheduled. If it is the + * case, 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(); + /* + * Check if the cpuidle framework is ready, otherwise fallback + * to the default arch specific idle method + */ if (cpuidle_enabled(drv, dev) == 0) { - /* ask the governor for the next state */ + /* + * Ask the governor to choose an idle state it thinks + * it is convenient to go to. There is *always* a + * convenient idle state + */ next_state = cpuidle_select(drv, dev); + /* + * 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 (current_clr_polling_and_test()) { dev->last_residency = 0; entered_state = next_state; @@ -104,7 +132,13 @@ static int cpuidle_idle_call(void) clockevents_notify( CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &dev->cpu); - + /* + * Enter the idle state previously returned by + * the governor decision. This function will + * block until an interrupt occurs and will + * take care of re-enabling the local + * interrupts + */ entered_state = cpuidle_enter(drv, dev, next_state); if (broadcast) @@ -164,6 +198,11 @@ static void cpu_idle_loop(void) if (cpu_idle_force_poll || tick_check_broadcast_expired()) cpu_idle_poll(); else + /* + * It is up to the underlying + * functions to enable the local + * interrupts again + */ cpuidle_idle_call(); arch_cpu_idle_exit();
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